![Nicola Corna](/assets/img/avatar_default.png)
As reported in the links given below. the BCM2835 has a hardware bug in its i2c module which prevents a correct clock stretching. This patch adds the I2C_AQ_NO_CLK_STRETCH quirk flag to i2c-bcm2835. Signed-off-by: Nicola Corna <nicola@corna.info> [wsa: put the links into the code as comments] Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
346 lines
8.7 KiB
C
346 lines
8.7 KiB
C
/*
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* BCM2835 master mode driver
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*
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* This software is licensed under the terms of the GNU General Public
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* License version 2, as published by the Free Software Foundation, and
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* may be copied, distributed, and modified under those terms.
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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/err.h>
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#include <linux/i2c.h>
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#include <linux/interrupt.h>
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#include <linux/io.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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#include <linux/slab.h>
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#define BCM2835_I2C_C 0x0
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#define BCM2835_I2C_S 0x4
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#define BCM2835_I2C_DLEN 0x8
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#define BCM2835_I2C_A 0xc
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#define BCM2835_I2C_FIFO 0x10
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#define BCM2835_I2C_DIV 0x14
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#define BCM2835_I2C_DEL 0x18
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#define BCM2835_I2C_CLKT 0x1c
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#define BCM2835_I2C_C_READ BIT(0)
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#define BCM2835_I2C_C_CLEAR BIT(4) /* bits 4 and 5 both clear */
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#define BCM2835_I2C_C_ST BIT(7)
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#define BCM2835_I2C_C_INTD BIT(8)
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#define BCM2835_I2C_C_INTT BIT(9)
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#define BCM2835_I2C_C_INTR BIT(10)
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#define BCM2835_I2C_C_I2CEN BIT(15)
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#define BCM2835_I2C_S_TA BIT(0)
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#define BCM2835_I2C_S_DONE BIT(1)
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#define BCM2835_I2C_S_TXW BIT(2)
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#define BCM2835_I2C_S_RXR BIT(3)
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#define BCM2835_I2C_S_TXD BIT(4)
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#define BCM2835_I2C_S_RXD BIT(5)
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#define BCM2835_I2C_S_TXE BIT(6)
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#define BCM2835_I2C_S_RXF BIT(7)
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#define BCM2835_I2C_S_ERR BIT(8)
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#define BCM2835_I2C_S_CLKT BIT(9)
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#define BCM2835_I2C_S_LEN BIT(10) /* Fake bit for SW error reporting */
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#define BCM2835_I2C_BITMSK_S 0x03FF
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#define BCM2835_I2C_CDIV_MIN 0x0002
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#define BCM2835_I2C_CDIV_MAX 0xFFFE
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#define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000))
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struct bcm2835_i2c_dev {
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struct device *dev;
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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 i2c_adapter adapter;
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struct completion completion;
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u32 msg_err;
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u8 *msg_buf;
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size_t msg_buf_remaining;
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};
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static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
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u32 reg, u32 val)
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{
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writel(val, i2c_dev->regs + reg);
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}
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static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
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{
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return readl(i2c_dev->regs + reg);
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}
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static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
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{
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u32 val;
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while (i2c_dev->msg_buf_remaining) {
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val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
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if (!(val & BCM2835_I2C_S_TXD))
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break;
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
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*i2c_dev->msg_buf);
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i2c_dev->msg_buf++;
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i2c_dev->msg_buf_remaining--;
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}
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}
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static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
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{
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u32 val;
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while (i2c_dev->msg_buf_remaining) {
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val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
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if (!(val & BCM2835_I2C_S_RXD))
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break;
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*i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
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BCM2835_I2C_FIFO);
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i2c_dev->msg_buf++;
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i2c_dev->msg_buf_remaining--;
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}
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}
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static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
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{
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struct bcm2835_i2c_dev *i2c_dev = data;
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u32 val, err;
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val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
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val &= BCM2835_I2C_BITMSK_S;
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val);
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err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
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if (err) {
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i2c_dev->msg_err = err;
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complete(&i2c_dev->completion);
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return IRQ_HANDLED;
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}
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if (val & BCM2835_I2C_S_RXD) {
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bcm2835_drain_rxfifo(i2c_dev);
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if (!(val & BCM2835_I2C_S_DONE))
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return IRQ_HANDLED;
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}
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if (val & BCM2835_I2C_S_DONE) {
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if (i2c_dev->msg_buf_remaining)
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i2c_dev->msg_err = BCM2835_I2C_S_LEN;
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else
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i2c_dev->msg_err = 0;
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complete(&i2c_dev->completion);
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return IRQ_HANDLED;
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}
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if (val & BCM2835_I2C_S_TXD) {
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bcm2835_fill_txfifo(i2c_dev);
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return IRQ_HANDLED;
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}
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return IRQ_NONE;
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}
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static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
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struct i2c_msg *msg)
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{
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u32 c;
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unsigned long time_left;
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i2c_dev->msg_buf = msg->buf;
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i2c_dev->msg_buf_remaining = msg->len;
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reinit_completion(&i2c_dev->completion);
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
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if (msg->flags & I2C_M_RD) {
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c = BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
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} else {
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c = BCM2835_I2C_C_INTT;
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bcm2835_fill_txfifo(i2c_dev);
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}
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c |= BCM2835_I2C_C_ST | BCM2835_I2C_C_INTD | BCM2835_I2C_C_I2CEN;
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
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time_left = wait_for_completion_timeout(&i2c_dev->completion,
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BCM2835_I2C_TIMEOUT);
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
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if (!time_left) {
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dev_err(i2c_dev->dev, "i2c transfer timed out\n");
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return -ETIMEDOUT;
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}
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if (likely(!i2c_dev->msg_err))
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return 0;
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if ((i2c_dev->msg_err & BCM2835_I2C_S_ERR) &&
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(msg->flags & I2C_M_IGNORE_NAK))
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return 0;
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dev_err(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
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if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
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return -EREMOTEIO;
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else
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return -EIO;
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}
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static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
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int num)
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{
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struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
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int i;
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int ret = 0;
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for (i = 0; i < num; i++) {
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ret = bcm2835_i2c_xfer_msg(i2c_dev, &msgs[i]);
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if (ret)
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break;
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}
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return ret ?: i;
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}
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static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
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{
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return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
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}
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static const struct i2c_algorithm bcm2835_i2c_algo = {
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.master_xfer = bcm2835_i2c_xfer,
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.functionality = bcm2835_i2c_func,
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};
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/*
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* This HW was reported to have problems with clock stretching:
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* http://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
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* https://www.raspberrypi.org/forums/viewtopic.php?p=146272
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*/
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static const struct i2c_adapter_quirks bcm2835_i2c_quirks = {
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.flags = I2C_AQ_NO_CLK_STRETCH,
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};
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static int bcm2835_i2c_probe(struct platform_device *pdev)
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{
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struct bcm2835_i2c_dev *i2c_dev;
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struct resource *mem, *irq;
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u32 bus_clk_rate, divider;
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int ret;
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struct i2c_adapter *adap;
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i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
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if (!i2c_dev)
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return -ENOMEM;
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platform_set_drvdata(pdev, i2c_dev);
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i2c_dev->dev = &pdev->dev;
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init_completion(&i2c_dev->completion);
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mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem);
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if (IS_ERR(i2c_dev->regs))
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return PTR_ERR(i2c_dev->regs);
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i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
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if (IS_ERR(i2c_dev->clk)) {
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dev_err(&pdev->dev, "Could not get clock\n");
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return PTR_ERR(i2c_dev->clk);
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}
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ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
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&bus_clk_rate);
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if (ret < 0) {
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dev_warn(&pdev->dev,
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"Could not read clock-frequency property\n");
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bus_clk_rate = 100000;
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}
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divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), bus_clk_rate);
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/*
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* Per the datasheet, the register is always interpreted as an even
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* number, by rounding down. In other words, the LSB is ignored. So,
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* if the LSB is set, increment the divider to avoid any issue.
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*/
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if (divider & 1)
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divider++;
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if ((divider < BCM2835_I2C_CDIV_MIN) ||
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(divider > BCM2835_I2C_CDIV_MAX)) {
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dev_err(&pdev->dev, "Invalid clock-frequency\n");
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return -ENODEV;
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}
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
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irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
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if (!irq) {
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dev_err(&pdev->dev, "No IRQ resource\n");
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return -ENODEV;
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}
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i2c_dev->irq = irq->start;
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ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
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dev_name(&pdev->dev), i2c_dev);
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if (ret) {
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dev_err(&pdev->dev, "Could not request IRQ\n");
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return -ENODEV;
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}
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adap = &i2c_dev->adapter;
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i2c_set_adapdata(adap, i2c_dev);
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adap->owner = THIS_MODULE;
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adap->class = I2C_CLASS_DEPRECATED;
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strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name));
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adap->algo = &bcm2835_i2c_algo;
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adap->dev.parent = &pdev->dev;
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adap->dev.of_node = pdev->dev.of_node;
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adap->quirks = &bcm2835_i2c_quirks;
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
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ret = i2c_add_adapter(adap);
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if (ret)
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free_irq(i2c_dev->irq, i2c_dev);
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return ret;
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}
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static int bcm2835_i2c_remove(struct platform_device *pdev)
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{
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struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
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free_irq(i2c_dev->irq, i2c_dev);
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i2c_del_adapter(&i2c_dev->adapter);
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return 0;
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}
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static const struct of_device_id bcm2835_i2c_of_match[] = {
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{ .compatible = "brcm,bcm2835-i2c" },
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{},
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};
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MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
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static struct platform_driver bcm2835_i2c_driver = {
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.probe = bcm2835_i2c_probe,
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.remove = bcm2835_i2c_remove,
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.driver = {
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.name = "i2c-bcm2835",
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.of_match_table = bcm2835_i2c_of_match,
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},
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};
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module_platform_driver(bcm2835_i2c_driver);
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MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
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MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
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MODULE_LICENSE("GPL v2");
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MODULE_ALIAS("platform:i2c-bcm2835");
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