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i2c: st: Implement bus clear 

>From I2C specifications:
      http://www.nxp.com/documents/user_manual/UM10204.pdf

Chapter 3.1.16, when the i2c device held the SDA line low, the master
should send 9 clocks pulses to try to recover.

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Peter Griffin 2016-05-11 17:21:59 +01:00 committed by Wolfram Sang
parent 3a9ddaf4dc
commit 40027b2fff
1 changed files with 44 additions and 1 deletions
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45
drivers/i2c/busses/i2c-st.c
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@ -337,10 +337,42 @@ static void st_i2c_hw_config(struct st_i2c_dev *i2c_dev)
writel_relaxed(val, i2c_dev->base + SSC_NOISE_SUPP_WIDTH_DATAOUT);
}
static int st_i2c_recover_bus(struct i2c_adapter *i2c_adap)
{
struct st_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
u32 ctl;
dev_dbg(i2c_dev->dev, "Trying to recover bus\n");
/*
* SSP IP is dual role SPI/I2C to generate 9 clock pulses
* we switch to SPI node, 9 bit words and write a 0. This
* has been validate with a oscilloscope and is easier
* than switching to GPIO mode.
*/
/* Disable interrupts */
writel_relaxed(0, i2c_dev->base + SSC_IEN);
st_i2c_hw_config(i2c_dev);
ctl = SSC_CTL_EN | SSC_CTL_MS | SSC_CTL_EN_RX_FIFO | SSC_CTL_EN_TX_FIFO;
st_i2c_set_bits(i2c_dev->base + SSC_CTL, ctl);
st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_I2CM);
usleep_range(8000, 10000);
writel_relaxed(0, i2c_dev->base + SSC_TBUF);
usleep_range(2000, 4000);
st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_I2CM);
return 0;
}
static int st_i2c_wait_free_bus(struct st_i2c_dev *i2c_dev)
{
u32 sta;
int i;
int i, ret;
for (i = 0; i < 10; i++) {
sta = readl_relaxed(i2c_dev->base + SSC_STA);
@ -352,6 +384,12 @@ static int st_i2c_wait_free_bus(struct st_i2c_dev *i2c_dev)
dev_err(i2c_dev->dev, "bus not free (status = 0x%08x)\n", sta);
ret = i2c_recover_bus(&i2c_dev->adap);
if (ret) {
dev_err(i2c_dev->dev, "Failed to recover the bus (%d)\n", ret);
return ret;
}
return -EBUSY;
}
@ -743,6 +781,10 @@ static struct i2c_algorithm st_i2c_algo = {
.functionality = st_i2c_func,
};
static struct i2c_bus_recovery_info st_i2c_recovery_info = {
.recover_bus = st_i2c_recover_bus,
};
static int st_i2c_of_get_deglitch(struct device_node *np,
struct st_i2c_dev *i2c_dev)
{
@ -825,6 +867,7 @@ static int st_i2c_probe(struct platform_device *pdev)
adap->timeout = 2 * HZ;
adap->retries = 0;
adap->algo = &st_i2c_algo;
adap->bus_recovery_info = &st_i2c_recovery_info;
adap->dev.parent = &pdev->dev;
adap->dev.of_node = pdev->dev.of_node;