Hi Philby,
On Wed, Jan 27, 2010 at 05:11:33, Kevin Hilman wrote:
> From: Philby John <pjohn@xxxxxxxxxxxxx>
>
> Come out of i2c time out condition by following the
> bus recovery procedure outlined in the i2c protocol v3 spec.
> The kernel must be robust enough to gracefully recover
> from i2c bus failure without having to reset the machine.
> This is done by first NACKing the slave, pulsing the SCL
> line 9 times and then sending the stop command.
>
> This patch has been tested on a DM6446 and DM355
>
> Signed-off-by: Philby John <pjohn@xxxxxxxxxxxxx>
> Signed-off-by: Srinivasan, Nageswari <nageswari@xxxxxx>
> Acked-by: Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-davinci.c | 57 +++++++++++++++++++++++++++++++++++--
> 1 files changed, 53 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
> index 35f9daa..5459065 100644
> --- a/drivers/i2c/busses/i2c-davinci.c
> +++ b/drivers/i2c/busses/i2c-davinci.c
> @@ -36,6 +36,7 @@
> #include <linux/platform_device.h>
> #include <linux/io.h>
> #include <linux/cpufreq.h>
> +#include <linux/gpio.h>
>
> #include <mach/hardware.h>
> #include <mach/i2c.h>
> @@ -43,6 +44,7 @@
> /* ----- global defines ----------------------------------------------- */
>
> #define DAVINCI_I2C_TIMEOUT (1*HZ)
> +#define DAVINCI_I2C_MAX_TRIES 2
> #define I2C_DAVINCI_INTR_ALL (DAVINCI_I2C_IMR_AAS | \
> DAVINCI_I2C_IMR_SCD | \
> DAVINCI_I2C_IMR_ARDY | \
> @@ -130,6 +132,44 @@ static inline u16 davinci_i2c_read_reg(struct davinci_i2c_dev *i2c_dev, int reg)
> return __raw_readw(i2c_dev->base + reg);
> }
>
> +/* Generate a pulse on the i2c clock pin. */
> +static void generic_i2c_clock_pulse(unsigned int scl_pin)
> +{
> + u16 i;
> +
> + if (scl_pin) {
> + /* Send high and low on the SCL line */
> + for (i = 0; i < 9; i++) {
> + gpio_set_value(scl_pin, 0);
> + udelay(20);
> + gpio_set_value(scl_pin, 1);
> + udelay(20);
> + }
Before using the pins as GPIO, you would have to set the
functionality of these pins as GPIO. You had this code in
previous incarnations of this patch - not sure why it is
dropped now.
Couple of good to haves:
It will be good to do a gpio_request() before using the pins
as GPIO - though I can see it may have been deemed unnecessary
- the pins are owned by I2C already - even so it may help catch
system configuration errors in later platforms.
The I2C peripheral on da8xx itself contains a mode where its
pins could be used as GPIO - so no need for SoC level muxing
and need for the platform data. This seems to be missing from
DM355 though. Thankfully there is a revision id within the I2C
memory map which will help you differentiate the two cases
(revision 0x5 vs 0x6)
Thanks,
Sekhar
> + }
> +}
> +
> +/* This routine does i2c bus recovery as specified in the
> + * i2c protocol Rev. 03 section 3.16 titled "Bus clear"
> + */
> +static void i2c_recover_bus(struct davinci_i2c_dev *dev)
> +{
> + u32 flag = 0;
> + struct davinci_i2c_platform_data *pdata = dev->dev->platform_data;
> +
> + dev_err(dev->dev, "initiating i2c bus recovery\n");
> + /* Send NACK to the slave */
> + flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
> + flag |= DAVINCI_I2C_MDR_NACK;
> + /* write the data into mode register */
> + davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
> + if (pdata)
> + generic_i2c_clock_pulse(pdata->scl_pin);
> + /* Send STOP */
> + flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
> + flag |= DAVINCI_I2C_MDR_STP;
> + davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
> +}
> +
> static inline void davinci_i2c_reset_ctrl(struct davinci_i2c_dev *i2c_dev,
> int val)
> {
> @@ -235,14 +275,22 @@ static int i2c_davinci_wait_bus_not_busy(struct davinci_i2c_dev *dev,
> char allow_sleep)
> {
> unsigned long timeout;
> + static u16 to_cnt;
>
> timeout = jiffies + dev->adapter.timeout;
> while (davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG)
> & DAVINCI_I2C_STR_BB) {
> - if (time_after(jiffies, timeout)) {
> - dev_warn(dev->dev,
> - "timeout waiting for bus ready\n");
> - return -ETIMEDOUT;
> + if (to_cnt <= DAVINCI_I2C_MAX_TRIES) {
> + if (time_after(jiffies, timeout)) {
> + dev_warn(dev->dev,
> + "timeout waiting for bus ready\n");
> + to_cnt++;
> + return -ETIMEDOUT;
> + } else {
> + to_cnt = 0;
> + i2c_recover_bus(dev);
> + i2c_davinci_init(dev);
> + }
> }
> if (allow_sleep)
> schedule_timeout(1);
> @@ -324,6 +372,7 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
> dev->adapter.timeout);
> if (r == 0) {
> dev_err(dev->dev, "controller timed out\n");
> + i2c_recover_bus(dev);
> i2c_davinci_init(dev);
> dev->buf_len = 0;
> return -ETIMEDOUT;
> --
> 1.6.6
>
> _______________________________________________
> Davinci-linux-open-source mailing list
> Davinci-linux-open-source@xxxxxxxxxxxxxxxxxxxx
> http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
>
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