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alistair23-linux/drivers/spi/spi-oc-tiny.c
Linus Walleij f03ee2042b
spi: oc-tiny: Use GPIO descriptors 
Switch the OC Tiny driver over to handling CS GPIOs using
GPIO descriptors in the core.

This driver is entirely relying on GPIOs to be used for
chipselect, so let the core pick these out using either
device tree or machine descriptors.

There are no in-tree users of this driver so no board files
need to be patched, out-of-tree boardfiles can use machine
descriptor tables, c.f. commit 1dfbf334f1.

Cc: Thomas Chou <thomas@wytron.com.tw>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20191205092411.64341-1-linus.walleij@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>
2019-12-27 01:08:11 +00:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* OpenCores tiny SPI master driver
*
* http://opencores.org/project,tiny_spi
*
* Copyright (C) 2011 Thomas Chou <thomas@wytron.com.tw>
*
* Based on spi_s3c24xx.c, which is:
* Copyright (c) 2006 Ben Dooks
* Copyright (c) 2006 Simtec Electronics
* Ben Dooks <ben@simtec.co.uk>
*/
#include <linux/interrupt.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/spi/spi_oc_tiny.h>
#include <linux/io.h>
#include <linux/of.h>
#define DRV_NAME "spi_oc_tiny"
#define TINY_SPI_RXDATA 0
#define TINY_SPI_TXDATA 4
#define TINY_SPI_STATUS 8
#define TINY_SPI_CONTROL 12
#define TINY_SPI_BAUD 16
#define TINY_SPI_STATUS_TXE 0x1
#define TINY_SPI_STATUS_TXR 0x2
struct tiny_spi {
/* bitbang has to be first */
struct spi_bitbang bitbang;
struct completion done;
void __iomem *base;
int irq;
unsigned int freq;
unsigned int baudwidth;
unsigned int baud;
unsigned int speed_hz;
unsigned int mode;
unsigned int len;
unsigned int txc, rxc;
const u8 *txp;
u8 *rxp;
};
static inline struct tiny_spi *tiny_spi_to_hw(struct spi_device *sdev)
{
return spi_master_get_devdata(sdev->master);
}
static unsigned int tiny_spi_baud(struct spi_device *spi, unsigned int hz)
{
struct tiny_spi *hw = tiny_spi_to_hw(spi);
return min(DIV_ROUND_UP(hw->freq, hz * 2), (1U << hw->baudwidth)) - 1;
}
static int tiny_spi_setup_transfer(struct spi_device *spi,
struct spi_transfer *t)
{
struct tiny_spi *hw = tiny_spi_to_hw(spi);
unsigned int baud = hw->baud;
if (t) {
if (t->speed_hz && t->speed_hz != hw->speed_hz)
baud = tiny_spi_baud(spi, t->speed_hz);
}
writel(baud, hw->base + TINY_SPI_BAUD);
writel(hw->mode, hw->base + TINY_SPI_CONTROL);
return 0;
}
static int tiny_spi_setup(struct spi_device *spi)
{
struct tiny_spi *hw = tiny_spi_to_hw(spi);
if (spi->max_speed_hz != hw->speed_hz) {
hw->speed_hz = spi->max_speed_hz;
hw->baud = tiny_spi_baud(spi, hw->speed_hz);
}
hw->mode = spi->mode & (SPI_CPOL | SPI_CPHA);
return 0;
}
static inline void tiny_spi_wait_txr(struct tiny_spi *hw)
{
while (!(readb(hw->base + TINY_SPI_STATUS) &
TINY_SPI_STATUS_TXR))
cpu_relax();
}
static inline void tiny_spi_wait_txe(struct tiny_spi *hw)
{
while (!(readb(hw->base + TINY_SPI_STATUS) &
TINY_SPI_STATUS_TXE))
cpu_relax();
}
static int tiny_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
{
struct tiny_spi *hw = tiny_spi_to_hw(spi);
const u8 *txp = t->tx_buf;
u8 *rxp = t->rx_buf;
unsigned int i;
if (hw->irq >= 0) {
/* use interrupt driven data transfer */
hw->len = t->len;
hw->txp = t->tx_buf;
hw->rxp = t->rx_buf;
hw->txc = 0;
hw->rxc = 0;
/* send the first byte */
if (t->len > 1) {
writeb(hw->txp ? *hw->txp++ : 0,
hw->base + TINY_SPI_TXDATA);
hw->txc++;
writeb(hw->txp ? *hw->txp++ : 0,
hw->base + TINY_SPI_TXDATA);
hw->txc++;
writeb(TINY_SPI_STATUS_TXR, hw->base + TINY_SPI_STATUS);
} else {
writeb(hw->txp ? *hw->txp++ : 0,
hw->base + TINY_SPI_TXDATA);
hw->txc++;
writeb(TINY_SPI_STATUS_TXE, hw->base + TINY_SPI_STATUS);
}
wait_for_completion(&hw->done);
} else {
/* we need to tighten the transfer loop */
writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);
for (i = 1; i < t->len; i++) {
writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);
if (rxp || (i != t->len - 1))
tiny_spi_wait_txr(hw);
if (rxp)
*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
}
tiny_spi_wait_txe(hw);
if (rxp)
*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
}
return t->len;
}
static irqreturn_t tiny_spi_irq(int irq, void *dev)
{
struct tiny_spi *hw = dev;
writeb(0, hw->base + TINY_SPI_STATUS);
if (hw->rxc + 1 == hw->len) {
if (hw->rxp)
*hw->rxp++ = readb(hw->base + TINY_SPI_RXDATA);
hw->rxc++;
complete(&hw->done);
} else {
if (hw->rxp)
*hw->rxp++ = readb(hw->base + TINY_SPI_TXDATA);
hw->rxc++;
if (hw->txc < hw->len) {
writeb(hw->txp ? *hw->txp++ : 0,
hw->base + TINY_SPI_TXDATA);
hw->txc++;
writeb(TINY_SPI_STATUS_TXR,
hw->base + TINY_SPI_STATUS);
} else {
writeb(TINY_SPI_STATUS_TXE,
hw->base + TINY_SPI_STATUS);
}
}
return IRQ_HANDLED;
}
#ifdef CONFIG_OF
#include <linux/of_gpio.h>
static int tiny_spi_of_probe(struct platform_device *pdev)
{
struct tiny_spi *hw = platform_get_drvdata(pdev);
struct device_node *np = pdev->dev.of_node;
u32 val;
if (!np)
return 0;
hw->bitbang.master->dev.of_node = pdev->dev.of_node;
if (!of_property_read_u32(np, "clock-frequency", &val))
hw->freq = val;
if (!of_property_read_u32(np, "baud-width", &val))
hw->baudwidth = val;
return 0;
}
#else /* !CONFIG_OF */
static int tiny_spi_of_probe(struct platform_device *pdev)
{
return 0;
}
#endif /* CONFIG_OF */
static int tiny_spi_probe(struct platform_device *pdev)
{
struct tiny_spi_platform_data *platp = dev_get_platdata(&pdev->dev);
struct tiny_spi *hw;
struct spi_master *master;
int err = -ENODEV;
master = spi_alloc_master(&pdev->dev, sizeof(struct tiny_spi));
if (!master)
return err;
/* setup the master state. */
master->bus_num = pdev->id;
master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
master->setup = tiny_spi_setup;
master->use_gpio_descriptors = true;
hw = spi_master_get_devdata(master);
platform_set_drvdata(pdev, hw);
/* setup the state for the bitbang driver */
hw->bitbang.master = master;
hw->bitbang.setup_transfer = tiny_spi_setup_transfer;
hw->bitbang.txrx_bufs = tiny_spi_txrx_bufs;
/* find and map our resources */
hw->base = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(hw->base)) {
err = PTR_ERR(hw->base);
goto exit;
}
/* irq is optional */
hw->irq = platform_get_irq(pdev, 0);
if (hw->irq >= 0) {
init_completion(&hw->done);
err = devm_request_irq(&pdev->dev, hw->irq, tiny_spi_irq, 0,
pdev->name, hw);
if (err)
goto exit;
}
/* find platform data */
if (platp) {
hw->freq = platp->freq;
hw->baudwidth = platp->baudwidth;
} else {
err = tiny_spi_of_probe(pdev);
if (err)
goto exit;
}
/* register our spi controller */
err = spi_bitbang_start(&hw->bitbang);
if (err)
goto exit;
dev_info(&pdev->dev, "base %p, irq %d\n", hw->base, hw->irq);
return 0;
exit:
spi_master_put(master);
return err;
}
static int tiny_spi_remove(struct platform_device *pdev)
{
struct tiny_spi *hw = platform_get_drvdata(pdev);
struct spi_master *master = hw->bitbang.master;
spi_bitbang_stop(&hw->bitbang);
spi_master_put(master);
return 0;
}
#ifdef CONFIG_OF
static const struct of_device_id tiny_spi_match[] = {
{ .compatible = "opencores,tiny-spi-rtlsvn2", },
{},
};
MODULE_DEVICE_TABLE(of, tiny_spi_match);
#endif /* CONFIG_OF */
static struct platform_driver tiny_spi_driver = {
.probe = tiny_spi_probe,
.remove = tiny_spi_remove,
.driver = {
.name = DRV_NAME,
.pm = NULL,
.of_match_table = of_match_ptr(tiny_spi_match),
},
};
module_platform_driver(tiny_spi_driver);
MODULE_DESCRIPTION("OpenCores tiny SPI driver");
MODULE_AUTHOR("Thomas Chou <thomas@wytron.com.tw>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRV_NAME);
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