In the event that a I2C bus is disturbed, for instance by a slave missing
a clock pulse, it is desirable to have a way to get the bus back working
other than by power-cycling the whole system. This patch makes it possible to
to have a special function in board support code issue an I2C reset, since
the IMX peripheral is not capable of doing this, and it needs to be done
by bit-banging the corresponding pins in GPIO mode.
The reset function needs to check if the bus is hung by checking the state
of SDA and issue a reset by pulsing SCL a few times as long as SDA is low.
Signed-off-by: David Jander <david@xxxxxxxxxxx>
---
arch/arm/plat-mxc/include/mach/i2c.h | 2 ++
drivers/i2c/busses/i2c-imx.c | 6 ++++++
2 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/arch/arm/plat-mxc/include/mach/i2c.h b/arch/arm/plat-mxc/include/mach/i2c.h
index 4a5dc5c..7ed4f64 100644
--- a/arch/arm/plat-mxc/include/mach/i2c.h
+++ b/arch/arm/plat-mxc/include/mach/i2c.h
@@ -13,12 +13,14 @@
* struct imxi2c_platform_data - structure of platform data for MXC I2C driver
* @init: Initialise gpio's and other board specific things
* @exit: Free everything initialised by @init
+ * @reset: Issue I2C reset if needed (toggle SCL via GPIO access)
* @bitrate: Bus speed measured in Hz
*
**/
struct imxi2c_platform_data {
int (*init)(struct device *dev);
void (*exit)(struct device *dev);
+ int (*reset)(struct device *dev);
int bitrate;
};
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 4c2a62b..c5c5cec 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -123,6 +123,7 @@ struct imx_i2c_struct {
unsigned int disable_delay;
int stopped;
unsigned int ifdr; /* IMX_I2C_IFDR */
+ int (*reset)(struct device *dev);
};
/** Functions for IMX I2C adapter driver ***************************************
@@ -197,6 +198,10 @@ static int i2c_imx_start(struct imx_i2c_struct *i2c_imx)
/* Wait controller to be stable */
udelay(50);
+ /* Check if bus is busy (hung if not multi-master) and issue reset */
+ if (i2c_imx->reset && i2c_imx->reset(&i2c_imx->adapter.dev))
+ return -ETIMEDOUT;
+
/* Start I2C transaction */
temp = readb(i2c_imx->base + IMX_I2C_I2CR);
temp |= I2CR_MSTA;
@@ -523,6 +528,7 @@ static int __init i2c_imx_probe(struct platform_device *pdev)
i2c_imx->irq = irq;
i2c_imx->base = base;
i2c_imx->res = res;
+ i2c_imx->reset = pdata->reset;
/* Get I2C clock */
i2c_imx->clk = clk_get(&pdev->dev, "i2c_clk");
--
1.7.5.4
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