![Meghana Madhyastha](/assets/img/avatar_default.png)
Split spi transfers into chunks of <=65532 to enable the driver to perform DMA transfer on big buffers. The DLEN register specifies the number of bytes to transfer in DMA mode. It is 16-bit wide and thus the maximum DMA transfer is 65535 bytes. Set the maximum to 65532 (4 byte aligned) since the FIFO in DMA mode is accessed in 4 byte chunks. ->max_dma_len is the value the spi core uses when splitting the buffer into scatter gather entries. The BCM2835 DMA block has 2 types of channels/engines: - Normal: Max length: 1G - Lite: Max length: 65535 Even when using a Lite channel we will not exceed the max length, so let's drop setting ->max_dma_len. Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> Reviewed-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Mark Brown <broonie@kernel.org>
1022 lines
28 KiB
C
1022 lines
28 KiB
C
/*
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* Driver for Broadcom BCM2835 SPI Controllers
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*
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* Copyright (C) 2012 Chris Boot
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* Copyright (C) 2013 Stephen Warren
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* Copyright (C) 2015 Martin Sperl
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*
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* This driver is inspired by:
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* spi-ath79.c, Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org>
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* spi-atmel.c, Copyright (C) 2006 Atmel Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/clk.h>
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#include <linux/completion.h>
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#include <linux/delay.h>
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#include <linux/dma-mapping.h>
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#include <linux/dmaengine.h>
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#include <linux/err.h>
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#include <linux/interrupt.h>
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#include <linux/io.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/of_address.h>
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#include <linux/of_device.h>
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#include <linux/of_gpio.h>
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#include <linux/of_irq.h>
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#include <linux/spi/spi.h>
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/* SPI register offsets */
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#define BCM2835_SPI_CS 0x00
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#define BCM2835_SPI_FIFO 0x04
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#define BCM2835_SPI_CLK 0x08
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#define BCM2835_SPI_DLEN 0x0c
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#define BCM2835_SPI_LTOH 0x10
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#define BCM2835_SPI_DC 0x14
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/* Bitfields in CS */
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#define BCM2835_SPI_CS_LEN_LONG 0x02000000
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#define BCM2835_SPI_CS_DMA_LEN 0x01000000
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#define BCM2835_SPI_CS_CSPOL2 0x00800000
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#define BCM2835_SPI_CS_CSPOL1 0x00400000
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#define BCM2835_SPI_CS_CSPOL0 0x00200000
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#define BCM2835_SPI_CS_RXF 0x00100000
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#define BCM2835_SPI_CS_RXR 0x00080000
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#define BCM2835_SPI_CS_TXD 0x00040000
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#define BCM2835_SPI_CS_RXD 0x00020000
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#define BCM2835_SPI_CS_DONE 0x00010000
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#define BCM2835_SPI_CS_LEN 0x00002000
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#define BCM2835_SPI_CS_REN 0x00001000
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#define BCM2835_SPI_CS_ADCS 0x00000800
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#define BCM2835_SPI_CS_INTR 0x00000400
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#define BCM2835_SPI_CS_INTD 0x00000200
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#define BCM2835_SPI_CS_DMAEN 0x00000100
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#define BCM2835_SPI_CS_TA 0x00000080
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#define BCM2835_SPI_CS_CSPOL 0x00000040
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#define BCM2835_SPI_CS_CLEAR_RX 0x00000020
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#define BCM2835_SPI_CS_CLEAR_TX 0x00000010
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#define BCM2835_SPI_CS_CPOL 0x00000008
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#define BCM2835_SPI_CS_CPHA 0x00000004
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#define BCM2835_SPI_CS_CS_10 0x00000002
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#define BCM2835_SPI_CS_CS_01 0x00000001
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#define BCM2835_SPI_FIFO_SIZE 64
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#define BCM2835_SPI_FIFO_SIZE_3_4 48
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#define BCM2835_SPI_POLLING_LIMIT_US 30
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#define BCM2835_SPI_POLLING_JIFFIES 2
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#define BCM2835_SPI_DMA_MIN_LENGTH 96
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#define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \
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| SPI_NO_CS | SPI_3WIRE)
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#define DRV_NAME "spi-bcm2835"
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/**
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* struct bcm2835_spi - BCM2835 SPI controller
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* @regs: base address of register map
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* @clk: core clock, divided to calculate serial clock
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* @irq: interrupt, signals TX FIFO empty or RX FIFO ¾ full
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* @tfr: SPI transfer currently processed
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* @tx_buf: pointer whence next transmitted byte is read
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* @rx_buf: pointer where next received byte is written
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* @tx_len: remaining bytes to transmit
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* @rx_len: remaining bytes to receive
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* @tx_prologue: bytes transmitted without DMA if first TX sglist entry's
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* length is not a multiple of 4 (to overcome hardware limitation)
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* @rx_prologue: bytes received without DMA if first RX sglist entry's
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* length is not a multiple of 4 (to overcome hardware limitation)
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* @tx_spillover: whether @tx_prologue spills over to second TX sglist entry
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* @dma_pending: whether a DMA transfer is in progress
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*/
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struct bcm2835_spi {
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void __iomem *regs;
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struct clk *clk;
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int irq;
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struct spi_transfer *tfr;
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const u8 *tx_buf;
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u8 *rx_buf;
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int tx_len;
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int rx_len;
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int tx_prologue;
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int rx_prologue;
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unsigned int tx_spillover;
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unsigned int dma_pending;
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};
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static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned reg)
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{
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return readl(bs->regs + reg);
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}
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static inline void bcm2835_wr(struct bcm2835_spi *bs, unsigned reg, u32 val)
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{
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writel(val, bs->regs + reg);
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}
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static inline void bcm2835_rd_fifo(struct bcm2835_spi *bs)
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{
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u8 byte;
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while ((bs->rx_len) &&
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(bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_RXD)) {
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byte = bcm2835_rd(bs, BCM2835_SPI_FIFO);
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if (bs->rx_buf)
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*bs->rx_buf++ = byte;
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bs->rx_len--;
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}
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}
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static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs)
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{
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u8 byte;
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while ((bs->tx_len) &&
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(bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_TXD)) {
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byte = bs->tx_buf ? *bs->tx_buf++ : 0;
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bcm2835_wr(bs, BCM2835_SPI_FIFO, byte);
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bs->tx_len--;
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}
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}
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/**
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* bcm2835_rd_fifo_count() - blindly read exactly @count bytes from RX FIFO
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* @bs: BCM2835 SPI controller
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* @count: bytes to read from RX FIFO
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*
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* The caller must ensure that @bs->rx_len is greater than or equal to @count,
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* that the RX FIFO contains at least @count bytes and that the DMA Enable flag
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* in the CS register is set (such that a read from the FIFO register receives
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* 32-bit instead of just 8-bit). Moreover @bs->rx_buf must not be %NULL.
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*/
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static inline void bcm2835_rd_fifo_count(struct bcm2835_spi *bs, int count)
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{
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u32 val;
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int len;
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bs->rx_len -= count;
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while (count > 0) {
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val = bcm2835_rd(bs, BCM2835_SPI_FIFO);
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len = min(count, 4);
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memcpy(bs->rx_buf, &val, len);
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bs->rx_buf += len;
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count -= 4;
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}
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}
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/**
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* bcm2835_wr_fifo_count() - blindly write exactly @count bytes to TX FIFO
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* @bs: BCM2835 SPI controller
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* @count: bytes to write to TX FIFO
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*
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* The caller must ensure that @bs->tx_len is greater than or equal to @count,
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* that the TX FIFO can accommodate @count bytes and that the DMA Enable flag
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* in the CS register is set (such that a write to the FIFO register transmits
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* 32-bit instead of just 8-bit).
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*/
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static inline void bcm2835_wr_fifo_count(struct bcm2835_spi *bs, int count)
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{
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u32 val;
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int len;
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bs->tx_len -= count;
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while (count > 0) {
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if (bs->tx_buf) {
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len = min(count, 4);
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memcpy(&val, bs->tx_buf, len);
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bs->tx_buf += len;
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} else {
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val = 0;
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}
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bcm2835_wr(bs, BCM2835_SPI_FIFO, val);
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count -= 4;
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}
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}
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/**
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* bcm2835_wait_tx_fifo_empty() - busy-wait for TX FIFO to empty
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* @bs: BCM2835 SPI controller
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*
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* The caller must ensure that the RX FIFO can accommodate as many bytes
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* as have been written to the TX FIFO: Transmission is halted once the
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* RX FIFO is full, causing this function to spin forever.
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*/
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static inline void bcm2835_wait_tx_fifo_empty(struct bcm2835_spi *bs)
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{
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while (!(bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_DONE))
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cpu_relax();
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}
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/**
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* bcm2835_rd_fifo_blind() - blindly read up to @count bytes from RX FIFO
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* @bs: BCM2835 SPI controller
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* @count: bytes available for reading in RX FIFO
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*/
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static inline void bcm2835_rd_fifo_blind(struct bcm2835_spi *bs, int count)
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{
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u8 val;
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count = min(count, bs->rx_len);
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bs->rx_len -= count;
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while (count) {
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val = bcm2835_rd(bs, BCM2835_SPI_FIFO);
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if (bs->rx_buf)
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*bs->rx_buf++ = val;
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count--;
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}
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}
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/**
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* bcm2835_wr_fifo_blind() - blindly write up to @count bytes to TX FIFO
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* @bs: BCM2835 SPI controller
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* @count: bytes available for writing in TX FIFO
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*/
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static inline void bcm2835_wr_fifo_blind(struct bcm2835_spi *bs, int count)
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{
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u8 val;
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count = min(count, bs->tx_len);
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bs->tx_len -= count;
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while (count) {
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val = bs->tx_buf ? *bs->tx_buf++ : 0;
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bcm2835_wr(bs, BCM2835_SPI_FIFO, val);
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count--;
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}
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}
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static void bcm2835_spi_reset_hw(struct spi_master *master)
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{
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struct bcm2835_spi *bs = spi_master_get_devdata(master);
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u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
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/* Disable SPI interrupts and transfer */
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cs &= ~(BCM2835_SPI_CS_INTR |
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BCM2835_SPI_CS_INTD |
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BCM2835_SPI_CS_DMAEN |
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BCM2835_SPI_CS_TA);
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/* and reset RX/TX FIFOS */
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cs |= BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX;
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/* and reset the SPI_HW */
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bcm2835_wr(bs, BCM2835_SPI_CS, cs);
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/* as well as DLEN */
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bcm2835_wr(bs, BCM2835_SPI_DLEN, 0);
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}
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static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id)
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{
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struct spi_master *master = dev_id;
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struct bcm2835_spi *bs = spi_master_get_devdata(master);
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u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
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/*
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* An interrupt is signaled either if DONE is set (TX FIFO empty)
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* or if RXR is set (RX FIFO >= ¾ full).
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*/
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if (cs & BCM2835_SPI_CS_RXF)
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bcm2835_rd_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE);
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else if (cs & BCM2835_SPI_CS_RXR)
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bcm2835_rd_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE_3_4);
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if (bs->tx_len && cs & BCM2835_SPI_CS_DONE)
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bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE);
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/* Read as many bytes as possible from FIFO */
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bcm2835_rd_fifo(bs);
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/* Write as many bytes as possible to FIFO */
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bcm2835_wr_fifo(bs);
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if (!bs->rx_len) {
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/* Transfer complete - reset SPI HW */
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bcm2835_spi_reset_hw(master);
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/* wake up the framework */
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complete(&master->xfer_completion);
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}
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return IRQ_HANDLED;
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}
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static int bcm2835_spi_transfer_one_irq(struct spi_master *master,
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struct spi_device *spi,
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struct spi_transfer *tfr,
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u32 cs, bool fifo_empty)
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{
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struct bcm2835_spi *bs = spi_master_get_devdata(master);
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/*
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* Enable HW block, but with interrupts still disabled.
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* Otherwise the empty TX FIFO would immediately trigger an interrupt.
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*/
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bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
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/* fill TX FIFO as much as possible */
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if (fifo_empty)
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bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE);
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bcm2835_wr_fifo(bs);
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/* enable interrupts */
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cs |= BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA;
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bcm2835_wr(bs, BCM2835_SPI_CS, cs);
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/* signal that we need to wait for completion */
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return 1;
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}
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/**
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* bcm2835_spi_transfer_prologue() - transfer first few bytes without DMA
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* @master: SPI master
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* @tfr: SPI transfer
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* @bs: BCM2835 SPI controller
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* @cs: CS register
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*
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* A limitation in DMA mode is that the FIFO must be accessed in 4 byte chunks.
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* Only the final write access is permitted to transmit less than 4 bytes, the
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* SPI controller deduces its intended size from the DLEN register.
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*
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* If a TX or RX sglist contains multiple entries, one per page, and the first
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* entry starts in the middle of a page, that first entry's length may not be
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* a multiple of 4. Subsequent entries are fine because they span an entire
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* page, hence do have a length that's a multiple of 4.
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*
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* This cannot happen with kmalloc'ed buffers (which is what most clients use)
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* because they are contiguous in physical memory and therefore not split on
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* page boundaries by spi_map_buf(). But it *can* happen with vmalloc'ed
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* buffers.
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*
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* The DMA engine is incapable of combining sglist entries into a continuous
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* stream of 4 byte chunks, it treats every entry separately: A TX entry is
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* rounded up a to a multiple of 4 bytes by transmitting surplus bytes, an RX
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* entry is rounded up by throwing away received bytes.
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*
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* Overcome this limitation by transferring the first few bytes without DMA:
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* E.g. if the first TX sglist entry's length is 23 and the first RX's is 42,
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* write 3 bytes to the TX FIFO but read only 2 bytes from the RX FIFO.
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* The residue of 1 byte in the RX FIFO is picked up by DMA. Together with
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* the rest of the first RX sglist entry it makes up a multiple of 4 bytes.
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*
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* Should the RX prologue be larger, say, 3 vis-à-vis a TX prologue of 1,
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* write 1 + 4 = 5 bytes to the TX FIFO and read 3 bytes from the RX FIFO.
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* Caution, the additional 4 bytes spill over to the second TX sglist entry
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* if the length of the first is *exactly* 1.
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*
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* At most 6 bytes are written and at most 3 bytes read. Do we know the
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* transfer has this many bytes? Yes, see BCM2835_SPI_DMA_MIN_LENGTH.
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*
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* The FIFO is normally accessed with 8-bit width by the CPU and 32-bit width
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* by the DMA engine. Toggling the DMA Enable flag in the CS register switches
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* the width but also garbles the FIFO's contents. The prologue must therefore
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* be transmitted in 32-bit width to ensure that the following DMA transfer can
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* pick up the residue in the RX FIFO in ungarbled form.
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*/
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static void bcm2835_spi_transfer_prologue(struct spi_master *master,
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struct spi_transfer *tfr,
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struct bcm2835_spi *bs,
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u32 cs)
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{
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int tx_remaining;
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bs->tfr = tfr;
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bs->tx_prologue = 0;
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bs->rx_prologue = 0;
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bs->tx_spillover = false;
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if (!sg_is_last(&tfr->tx_sg.sgl[0]))
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bs->tx_prologue = sg_dma_len(&tfr->tx_sg.sgl[0]) & 3;
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if (!sg_is_last(&tfr->rx_sg.sgl[0])) {
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bs->rx_prologue = sg_dma_len(&tfr->rx_sg.sgl[0]) & 3;
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if (bs->rx_prologue > bs->tx_prologue) {
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if (sg_is_last(&tfr->tx_sg.sgl[0])) {
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bs->tx_prologue = bs->rx_prologue;
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} else {
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bs->tx_prologue += 4;
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bs->tx_spillover =
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!(sg_dma_len(&tfr->tx_sg.sgl[0]) & ~3);
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}
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}
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}
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/* rx_prologue > 0 implies tx_prologue > 0, so check only the latter */
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if (!bs->tx_prologue)
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return;
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/* Write and read RX prologue. Adjust first entry in RX sglist. */
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if (bs->rx_prologue) {
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bcm2835_wr(bs, BCM2835_SPI_DLEN, bs->rx_prologue);
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bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA
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| BCM2835_SPI_CS_DMAEN);
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bcm2835_wr_fifo_count(bs, bs->rx_prologue);
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bcm2835_wait_tx_fifo_empty(bs);
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bcm2835_rd_fifo_count(bs, bs->rx_prologue);
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bcm2835_spi_reset_hw(master);
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dma_sync_single_for_device(master->dma_rx->device->dev,
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sg_dma_address(&tfr->rx_sg.sgl[0]),
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bs->rx_prologue, DMA_FROM_DEVICE);
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|
|
sg_dma_address(&tfr->rx_sg.sgl[0]) += bs->rx_prologue;
|
|
sg_dma_len(&tfr->rx_sg.sgl[0]) -= bs->rx_prologue;
|
|
}
|
|
|
|
/*
|
|
* Write remaining TX prologue. Adjust first entry in TX sglist.
|
|
* Also adjust second entry if prologue spills over to it.
|
|
*/
|
|
tx_remaining = bs->tx_prologue - bs->rx_prologue;
|
|
if (tx_remaining) {
|
|
bcm2835_wr(bs, BCM2835_SPI_DLEN, tx_remaining);
|
|
bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA
|
|
| BCM2835_SPI_CS_DMAEN);
|
|
bcm2835_wr_fifo_count(bs, tx_remaining);
|
|
bcm2835_wait_tx_fifo_empty(bs);
|
|
bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_CLEAR_TX);
|
|
}
|
|
|
|
if (likely(!bs->tx_spillover)) {
|
|
sg_dma_address(&tfr->tx_sg.sgl[0]) += bs->tx_prologue;
|
|
sg_dma_len(&tfr->tx_sg.sgl[0]) -= bs->tx_prologue;
|
|
} else {
|
|
sg_dma_len(&tfr->tx_sg.sgl[0]) = 0;
|
|
sg_dma_address(&tfr->tx_sg.sgl[1]) += 4;
|
|
sg_dma_len(&tfr->tx_sg.sgl[1]) -= 4;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* bcm2835_spi_undo_prologue() - reconstruct original sglist state
|
|
* @bs: BCM2835 SPI controller
|
|
*
|
|
* Undo changes which were made to an SPI transfer's sglist when transmitting
|
|
* the prologue. This is necessary to ensure the same memory ranges are
|
|
* unmapped that were originally mapped.
|
|
*/
|
|
static void bcm2835_spi_undo_prologue(struct bcm2835_spi *bs)
|
|
{
|
|
struct spi_transfer *tfr = bs->tfr;
|
|
|
|
if (!bs->tx_prologue)
|
|
return;
|
|
|
|
if (bs->rx_prologue) {
|
|
sg_dma_address(&tfr->rx_sg.sgl[0]) -= bs->rx_prologue;
|
|
sg_dma_len(&tfr->rx_sg.sgl[0]) += bs->rx_prologue;
|
|
}
|
|
|
|
if (likely(!bs->tx_spillover)) {
|
|
sg_dma_address(&tfr->tx_sg.sgl[0]) -= bs->tx_prologue;
|
|
sg_dma_len(&tfr->tx_sg.sgl[0]) += bs->tx_prologue;
|
|
} else {
|
|
sg_dma_len(&tfr->tx_sg.sgl[0]) = bs->tx_prologue - 4;
|
|
sg_dma_address(&tfr->tx_sg.sgl[1]) -= 4;
|
|
sg_dma_len(&tfr->tx_sg.sgl[1]) += 4;
|
|
}
|
|
}
|
|
|
|
static void bcm2835_spi_dma_done(void *data)
|
|
{
|
|
struct spi_master *master = data;
|
|
struct bcm2835_spi *bs = spi_master_get_devdata(master);
|
|
|
|
/* reset fifo and HW */
|
|
bcm2835_spi_reset_hw(master);
|
|
|
|
/* and terminate tx-dma as we do not have an irq for it
|
|
* because when the rx dma will terminate and this callback
|
|
* is called the tx-dma must have finished - can't get to this
|
|
* situation otherwise...
|
|
*/
|
|
if (cmpxchg(&bs->dma_pending, true, false)) {
|
|
dmaengine_terminate_async(master->dma_tx);
|
|
bcm2835_spi_undo_prologue(bs);
|
|
}
|
|
|
|
/* and mark as completed */;
|
|
complete(&master->xfer_completion);
|
|
}
|
|
|
|
static int bcm2835_spi_prepare_sg(struct spi_master *master,
|
|
struct spi_transfer *tfr,
|
|
bool is_tx)
|
|
{
|
|
struct dma_chan *chan;
|
|
struct scatterlist *sgl;
|
|
unsigned int nents;
|
|
enum dma_transfer_direction dir;
|
|
unsigned long flags;
|
|
|
|
struct dma_async_tx_descriptor *desc;
|
|
dma_cookie_t cookie;
|
|
|
|
if (is_tx) {
|
|
dir = DMA_MEM_TO_DEV;
|
|
chan = master->dma_tx;
|
|
nents = tfr->tx_sg.nents;
|
|
sgl = tfr->tx_sg.sgl;
|
|
flags = 0 /* no tx interrupt */;
|
|
|
|
} else {
|
|
dir = DMA_DEV_TO_MEM;
|
|
chan = master->dma_rx;
|
|
nents = tfr->rx_sg.nents;
|
|
sgl = tfr->rx_sg.sgl;
|
|
flags = DMA_PREP_INTERRUPT;
|
|
}
|
|
/* prepare the channel */
|
|
desc = dmaengine_prep_slave_sg(chan, sgl, nents, dir, flags);
|
|
if (!desc)
|
|
return -EINVAL;
|
|
|
|
/* set callback for rx */
|
|
if (!is_tx) {
|
|
desc->callback = bcm2835_spi_dma_done;
|
|
desc->callback_param = master;
|
|
}
|
|
|
|
/* submit it to DMA-engine */
|
|
cookie = dmaengine_submit(desc);
|
|
|
|
return dma_submit_error(cookie);
|
|
}
|
|
|
|
static int bcm2835_spi_transfer_one_dma(struct spi_master *master,
|
|
struct spi_device *spi,
|
|
struct spi_transfer *tfr,
|
|
u32 cs)
|
|
{
|
|
struct bcm2835_spi *bs = spi_master_get_devdata(master);
|
|
int ret;
|
|
|
|
/*
|
|
* Transfer first few bytes without DMA if length of first TX or RX
|
|
* sglist entry is not a multiple of 4 bytes (hardware limitation).
|
|
*/
|
|
bcm2835_spi_transfer_prologue(master, tfr, bs, cs);
|
|
|
|
/* setup tx-DMA */
|
|
ret = bcm2835_spi_prepare_sg(master, tfr, true);
|
|
if (ret)
|
|
goto err_reset_hw;
|
|
|
|
/* start TX early */
|
|
dma_async_issue_pending(master->dma_tx);
|
|
|
|
/* mark as dma pending */
|
|
bs->dma_pending = 1;
|
|
|
|
/* set the DMA length */
|
|
bcm2835_wr(bs, BCM2835_SPI_DLEN, bs->tx_len);
|
|
|
|
/* start the HW */
|
|
bcm2835_wr(bs, BCM2835_SPI_CS,
|
|
cs | BCM2835_SPI_CS_TA | BCM2835_SPI_CS_DMAEN);
|
|
|
|
/* setup rx-DMA late - to run transfers while
|
|
* mapping of the rx buffers still takes place
|
|
* this saves 10us or more.
|
|
*/
|
|
ret = bcm2835_spi_prepare_sg(master, tfr, false);
|
|
if (ret) {
|
|
/* need to reset on errors */
|
|
dmaengine_terminate_sync(master->dma_tx);
|
|
bs->dma_pending = false;
|
|
goto err_reset_hw;
|
|
}
|
|
|
|
/* start rx dma late */
|
|
dma_async_issue_pending(master->dma_rx);
|
|
|
|
/* wait for wakeup in framework */
|
|
return 1;
|
|
|
|
err_reset_hw:
|
|
bcm2835_spi_reset_hw(master);
|
|
bcm2835_spi_undo_prologue(bs);
|
|
return ret;
|
|
}
|
|
|
|
static bool bcm2835_spi_can_dma(struct spi_master *master,
|
|
struct spi_device *spi,
|
|
struct spi_transfer *tfr)
|
|
{
|
|
/* we start DMA efforts only on bigger transfers */
|
|
if (tfr->len < BCM2835_SPI_DMA_MIN_LENGTH)
|
|
return false;
|
|
|
|
/* return OK */
|
|
return true;
|
|
}
|
|
|
|
static void bcm2835_dma_release(struct spi_master *master)
|
|
{
|
|
if (master->dma_tx) {
|
|
dmaengine_terminate_sync(master->dma_tx);
|
|
dma_release_channel(master->dma_tx);
|
|
master->dma_tx = NULL;
|
|
}
|
|
if (master->dma_rx) {
|
|
dmaengine_terminate_sync(master->dma_rx);
|
|
dma_release_channel(master->dma_rx);
|
|
master->dma_rx = NULL;
|
|
}
|
|
}
|
|
|
|
static void bcm2835_dma_init(struct spi_master *master, struct device *dev)
|
|
{
|
|
struct dma_slave_config slave_config;
|
|
const __be32 *addr;
|
|
dma_addr_t dma_reg_base;
|
|
int ret;
|
|
|
|
/* base address in dma-space */
|
|
addr = of_get_address(master->dev.of_node, 0, NULL, NULL);
|
|
if (!addr) {
|
|
dev_err(dev, "could not get DMA-register address - not using dma mode\n");
|
|
goto err;
|
|
}
|
|
dma_reg_base = be32_to_cpup(addr);
|
|
|
|
/* get tx/rx dma */
|
|
master->dma_tx = dma_request_slave_channel(dev, "tx");
|
|
if (!master->dma_tx) {
|
|
dev_err(dev, "no tx-dma configuration found - not using dma mode\n");
|
|
goto err;
|
|
}
|
|
master->dma_rx = dma_request_slave_channel(dev, "rx");
|
|
if (!master->dma_rx) {
|
|
dev_err(dev, "no rx-dma configuration found - not using dma mode\n");
|
|
goto err_release;
|
|
}
|
|
|
|
/* configure DMAs */
|
|
slave_config.direction = DMA_MEM_TO_DEV;
|
|
slave_config.dst_addr = (u32)(dma_reg_base + BCM2835_SPI_FIFO);
|
|
slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
|
|
|
|
ret = dmaengine_slave_config(master->dma_tx, &slave_config);
|
|
if (ret)
|
|
goto err_config;
|
|
|
|
slave_config.direction = DMA_DEV_TO_MEM;
|
|
slave_config.src_addr = (u32)(dma_reg_base + BCM2835_SPI_FIFO);
|
|
slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
|
|
|
|
ret = dmaengine_slave_config(master->dma_rx, &slave_config);
|
|
if (ret)
|
|
goto err_config;
|
|
|
|
/* all went well, so set can_dma */
|
|
master->can_dma = bcm2835_spi_can_dma;
|
|
/* need to do TX AND RX DMA, so we need dummy buffers */
|
|
master->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;
|
|
|
|
return;
|
|
|
|
err_config:
|
|
dev_err(dev, "issue configuring dma: %d - not using DMA mode\n",
|
|
ret);
|
|
err_release:
|
|
bcm2835_dma_release(master);
|
|
err:
|
|
return;
|
|
}
|
|
|
|
static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
|
|
struct spi_device *spi,
|
|
struct spi_transfer *tfr,
|
|
u32 cs,
|
|
unsigned long long xfer_time_us)
|
|
{
|
|
struct bcm2835_spi *bs = spi_master_get_devdata(master);
|
|
unsigned long timeout;
|
|
|
|
/* enable HW block without interrupts */
|
|
bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
|
|
|
|
/* fill in the fifo before timeout calculations
|
|
* if we are interrupted here, then the data is
|
|
* getting transferred by the HW while we are interrupted
|
|
*/
|
|
bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE);
|
|
|
|
/* set the timeout */
|
|
timeout = jiffies + BCM2835_SPI_POLLING_JIFFIES;
|
|
|
|
/* loop until finished the transfer */
|
|
while (bs->rx_len) {
|
|
/* fill in tx fifo with remaining data */
|
|
bcm2835_wr_fifo(bs);
|
|
|
|
/* read from fifo as much as possible */
|
|
bcm2835_rd_fifo(bs);
|
|
|
|
/* if there is still data pending to read
|
|
* then check the timeout
|
|
*/
|
|
if (bs->rx_len && time_after(jiffies, timeout)) {
|
|
dev_dbg_ratelimited(&spi->dev,
|
|
"timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
|
|
jiffies - timeout,
|
|
bs->tx_len, bs->rx_len);
|
|
/* fall back to interrupt mode */
|
|
return bcm2835_spi_transfer_one_irq(master, spi,
|
|
tfr, cs, false);
|
|
}
|
|
}
|
|
|
|
/* Transfer complete - reset SPI HW */
|
|
bcm2835_spi_reset_hw(master);
|
|
/* and return without waiting for completion */
|
|
return 0;
|
|
}
|
|
|
|
static int bcm2835_spi_transfer_one(struct spi_master *master,
|
|
struct spi_device *spi,
|
|
struct spi_transfer *tfr)
|
|
{
|
|
struct bcm2835_spi *bs = spi_master_get_devdata(master);
|
|
unsigned long spi_hz, clk_hz, cdiv;
|
|
unsigned long spi_used_hz;
|
|
unsigned long long xfer_time_us;
|
|
u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
|
|
|
|
/* set clock */
|
|
spi_hz = tfr->speed_hz;
|
|
clk_hz = clk_get_rate(bs->clk);
|
|
|
|
if (spi_hz >= clk_hz / 2) {
|
|
cdiv = 2; /* clk_hz/2 is the fastest we can go */
|
|
} else if (spi_hz) {
|
|
/* CDIV must be a multiple of two */
|
|
cdiv = DIV_ROUND_UP(clk_hz, spi_hz);
|
|
cdiv += (cdiv % 2);
|
|
|
|
if (cdiv >= 65536)
|
|
cdiv = 0; /* 0 is the slowest we can go */
|
|
} else {
|
|
cdiv = 0; /* 0 is the slowest we can go */
|
|
}
|
|
spi_used_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536);
|
|
bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);
|
|
|
|
/* handle all the 3-wire mode */
|
|
if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf))
|
|
cs |= BCM2835_SPI_CS_REN;
|
|
else
|
|
cs &= ~BCM2835_SPI_CS_REN;
|
|
|
|
/*
|
|
* The driver always uses software-controlled GPIO Chip Select.
|
|
* Set the hardware-controlled native Chip Select to an invalid
|
|
* value to prevent it from interfering.
|
|
*/
|
|
cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01;
|
|
|
|
/* set transmit buffers and length */
|
|
bs->tx_buf = tfr->tx_buf;
|
|
bs->rx_buf = tfr->rx_buf;
|
|
bs->tx_len = tfr->len;
|
|
bs->rx_len = tfr->len;
|
|
|
|
/* calculate the estimated time in us the transfer runs */
|
|
xfer_time_us = (unsigned long long)tfr->len
|
|
* 9 /* clocks/byte - SPI-HW waits 1 clock after each byte */
|
|
* 1000000;
|
|
do_div(xfer_time_us, spi_used_hz);
|
|
|
|
/* for short requests run polling*/
|
|
if (xfer_time_us <= BCM2835_SPI_POLLING_LIMIT_US)
|
|
return bcm2835_spi_transfer_one_poll(master, spi, tfr,
|
|
cs, xfer_time_us);
|
|
|
|
/* run in dma mode if conditions are right */
|
|
if (master->can_dma && bcm2835_spi_can_dma(master, spi, tfr))
|
|
return bcm2835_spi_transfer_one_dma(master, spi, tfr, cs);
|
|
|
|
/* run in interrupt-mode */
|
|
return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs, true);
|
|
}
|
|
|
|
static int bcm2835_spi_prepare_message(struct spi_master *master,
|
|
struct spi_message *msg)
|
|
{
|
|
struct spi_device *spi = msg->spi;
|
|
struct bcm2835_spi *bs = spi_master_get_devdata(master);
|
|
u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
|
|
int ret;
|
|
|
|
/*
|
|
* DMA transfers are limited to 16 bit (0 to 65535 bytes) by the SPI HW
|
|
* due to DLEN. Split up transfers (32-bit FIFO aligned) if the limit is
|
|
* exceeded.
|
|
*/
|
|
ret = spi_split_transfers_maxsize(master, msg, 65532,
|
|
GFP_KERNEL | GFP_DMA);
|
|
if (ret)
|
|
return ret;
|
|
|
|
cs &= ~(BCM2835_SPI_CS_CPOL | BCM2835_SPI_CS_CPHA);
|
|
|
|
if (spi->mode & SPI_CPOL)
|
|
cs |= BCM2835_SPI_CS_CPOL;
|
|
if (spi->mode & SPI_CPHA)
|
|
cs |= BCM2835_SPI_CS_CPHA;
|
|
|
|
bcm2835_wr(bs, BCM2835_SPI_CS, cs);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void bcm2835_spi_handle_err(struct spi_master *master,
|
|
struct spi_message *msg)
|
|
{
|
|
struct bcm2835_spi *bs = spi_master_get_devdata(master);
|
|
|
|
/* if an error occurred and we have an active dma, then terminate */
|
|
if (cmpxchg(&bs->dma_pending, true, false)) {
|
|
dmaengine_terminate_sync(master->dma_tx);
|
|
dmaengine_terminate_sync(master->dma_rx);
|
|
bcm2835_spi_undo_prologue(bs);
|
|
}
|
|
/* and reset */
|
|
bcm2835_spi_reset_hw(master);
|
|
}
|
|
|
|
static int chip_match_name(struct gpio_chip *chip, void *data)
|
|
{
|
|
return !strcmp(chip->label, data);
|
|
}
|
|
|
|
static int bcm2835_spi_setup(struct spi_device *spi)
|
|
{
|
|
int err;
|
|
struct gpio_chip *chip;
|
|
/*
|
|
* sanity checking the native-chipselects
|
|
*/
|
|
if (spi->mode & SPI_NO_CS)
|
|
return 0;
|
|
if (gpio_is_valid(spi->cs_gpio))
|
|
return 0;
|
|
if (spi->chip_select > 1) {
|
|
/* error in the case of native CS requested with CS > 1
|
|
* officially there is a CS2, but it is not documented
|
|
* which GPIO is connected with that...
|
|
*/
|
|
dev_err(&spi->dev,
|
|
"setup: only two native chip-selects are supported\n");
|
|
return -EINVAL;
|
|
}
|
|
/* now translate native cs to GPIO */
|
|
|
|
/* get the gpio chip for the base */
|
|
chip = gpiochip_find("pinctrl-bcm2835", chip_match_name);
|
|
if (!chip)
|
|
return 0;
|
|
|
|
/* and calculate the real CS */
|
|
spi->cs_gpio = chip->base + 8 - spi->chip_select;
|
|
|
|
/* and set up the "mode" and level */
|
|
dev_info(&spi->dev, "setting up native-CS%i as GPIO %i\n",
|
|
spi->chip_select, spi->cs_gpio);
|
|
|
|
/* set up GPIO as output and pull to the correct level */
|
|
err = gpio_direction_output(spi->cs_gpio,
|
|
(spi->mode & SPI_CS_HIGH) ? 0 : 1);
|
|
if (err) {
|
|
dev_err(&spi->dev,
|
|
"could not set CS%i gpio %i as output: %i",
|
|
spi->chip_select, spi->cs_gpio, err);
|
|
return err;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int bcm2835_spi_probe(struct platform_device *pdev)
|
|
{
|
|
struct spi_master *master;
|
|
struct bcm2835_spi *bs;
|
|
struct resource *res;
|
|
int err;
|
|
|
|
master = spi_alloc_master(&pdev->dev, sizeof(*bs));
|
|
if (!master) {
|
|
dev_err(&pdev->dev, "spi_alloc_master() failed\n");
|
|
return -ENOMEM;
|
|
}
|
|
|
|
platform_set_drvdata(pdev, master);
|
|
|
|
master->mode_bits = BCM2835_SPI_MODE_BITS;
|
|
master->bits_per_word_mask = SPI_BPW_MASK(8);
|
|
master->num_chipselect = 3;
|
|
master->setup = bcm2835_spi_setup;
|
|
master->transfer_one = bcm2835_spi_transfer_one;
|
|
master->handle_err = bcm2835_spi_handle_err;
|
|
master->prepare_message = bcm2835_spi_prepare_message;
|
|
master->dev.of_node = pdev->dev.of_node;
|
|
|
|
bs = spi_master_get_devdata(master);
|
|
|
|
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
|
|
bs->regs = devm_ioremap_resource(&pdev->dev, res);
|
|
if (IS_ERR(bs->regs)) {
|
|
err = PTR_ERR(bs->regs);
|
|
goto out_master_put;
|
|
}
|
|
|
|
bs->clk = devm_clk_get(&pdev->dev, NULL);
|
|
if (IS_ERR(bs->clk)) {
|
|
err = PTR_ERR(bs->clk);
|
|
dev_err(&pdev->dev, "could not get clk: %d\n", err);
|
|
goto out_master_put;
|
|
}
|
|
|
|
bs->irq = platform_get_irq(pdev, 0);
|
|
if (bs->irq <= 0) {
|
|
dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
|
|
err = bs->irq ? bs->irq : -ENODEV;
|
|
goto out_master_put;
|
|
}
|
|
|
|
clk_prepare_enable(bs->clk);
|
|
|
|
bcm2835_dma_init(master, &pdev->dev);
|
|
|
|
/* initialise the hardware with the default polarities */
|
|
bcm2835_wr(bs, BCM2835_SPI_CS,
|
|
BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
|
|
|
|
err = devm_request_irq(&pdev->dev, bs->irq, bcm2835_spi_interrupt, 0,
|
|
dev_name(&pdev->dev), master);
|
|
if (err) {
|
|
dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
|
|
goto out_clk_disable;
|
|
}
|
|
|
|
err = devm_spi_register_master(&pdev->dev, master);
|
|
if (err) {
|
|
dev_err(&pdev->dev, "could not register SPI master: %d\n", err);
|
|
goto out_clk_disable;
|
|
}
|
|
|
|
return 0;
|
|
|
|
out_clk_disable:
|
|
clk_disable_unprepare(bs->clk);
|
|
out_master_put:
|
|
spi_master_put(master);
|
|
return err;
|
|
}
|
|
|
|
static int bcm2835_spi_remove(struct platform_device *pdev)
|
|
{
|
|
struct spi_master *master = platform_get_drvdata(pdev);
|
|
struct bcm2835_spi *bs = spi_master_get_devdata(master);
|
|
|
|
/* Clear FIFOs, and disable the HW block */
|
|
bcm2835_wr(bs, BCM2835_SPI_CS,
|
|
BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
|
|
|
|
clk_disable_unprepare(bs->clk);
|
|
|
|
bcm2835_dma_release(master);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static const struct of_device_id bcm2835_spi_match[] = {
|
|
{ .compatible = "brcm,bcm2835-spi", },
|
|
{}
|
|
};
|
|
MODULE_DEVICE_TABLE(of, bcm2835_spi_match);
|
|
|
|
static struct platform_driver bcm2835_spi_driver = {
|
|
.driver = {
|
|
.name = DRV_NAME,
|
|
.of_match_table = bcm2835_spi_match,
|
|
},
|
|
.probe = bcm2835_spi_probe,
|
|
.remove = bcm2835_spi_remove,
|
|
};
|
|
module_platform_driver(bcm2835_spi_driver);
|
|
|
|
MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835");
|
|
MODULE_AUTHOR("Chris Boot <bootc@bootc.net>");
|
|
MODULE_LICENSE("GPL");
|