Re: [PATCH/RFC 1/1] recover from davinci i2c time out conditions

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Hello,



----- Original Message ----
> From: Philby John <pjohn@xxxxxxxxxxxxx>
> To: linux-i2c@xxxxxxxxxxxxxxx
> Cc: khali@xxxxxxxxxxxx; davinci-linux-open-source@xxxxxxxxxxxxxxxxxxxx
> Sent: Wednesday, July 15, 2009 13:04:27
> Subject: [PATCH/RFC 1/1] recover from davinci i2c time out conditions
> 
> >From dbe7e824d576636bb15b82a20fd2557fddc9a8f7 Mon Sep 17 00:00:00 2001
> From: Philby John 
> Date: Tue, 14 Jul 2009 21:46:47 +0530
> Subject: [PATCH] Reset i2c bus to come out of time out conditions
> 
> Get out of i2c time out condition by resetting
> the i2c bus. 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
> and then resetting the i2c bus after a certain timeout.
> 
> Signed-off-by: Philby John 

I tried this on DM6443 based board with 2.6.18 kernel. The result I am posting below. It gives controller time out again and again.

dhcppc9 login: i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery
i2c_davinci i2c_davinci.1: controller timed out
i2c_davinci i2c_davinci.1: initiating i2c bus recovery

regards

-Nitin
> ---
> drivers/i2c/busses/i2c-davinci.c |   98 +++++++++++++++++++++++++++++++++++--
> 1 files changed, 92 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
> index 17f2ee7..4ed1a4c 100755
> --- a/drivers/i2c/busses/i2c-davinci.c
> +++ b/drivers/i2c/busses/i2c-davinci.c
> @@ -35,14 +35,18 @@
> #include 
> #include 
> #include 
> +#include 
> 
> #include 
> 
> #include 
> +#include 
> +#include 
> 
> /* ----- 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 | \
> @@ -135,6 +139,50 @@ static inline u16 davinci_i2c_read_reg(struct 
> davinci_i2c_dev *i2c_dev, int reg)
> }
> 
> /*
> + * Configure the i2c data pin as a GPIO input and the i2c clock pin as a
> + * high GPIO output.
> + */
> +static void disable_i2c_pins(void)
> +{
> +    unsigned long flags;
> +
> +    local_irq_save(flags);
> +    if (cpu_is_davinci_dm355()) {
> +        gpio_direction_input(15);
> +        gpio_direction_output(14, 0);
> +        gpio_set_value(14, 1);
> +        davinci_cfg_reg(DM355_I2C_SDA);
> +        davinci_cfg_reg(DM355_I2C_SCL);
> +    }
> +    local_irq_restore(flags);
> +}
> +
> +/* Connect the i2c pins to the i2c controller. */
> +static void enable_i2c_pins(void)
> +{
> +    unsigned long flags;
> +
> +    local_irq_save(flags);
> +    if (cpu_is_davinci_dm355()) {
> +        davinci_cfg_reg(DM355_I2C_SDA);
> +        davinci_cfg_reg(DM355_I2C_SCL);
> +    }
> +    local_irq_restore(flags);
> +}
> +
> +
> +/* Generate a pulse on the i2c clock pin. */
> +static void pulse_i2c_clock(void)
> +{
> +    if (cpu_is_davinci_dm355()) {
> +        gpio_set_value(14, 0);
> +        udelay(20);
> +        gpio_set_value(14, 1);
> +        udelay(20);
> +    }
> +}
> +
> +/*
>   * This functions configures I2C and brings I2C out of reset.
>   * This function is called during I2C init function. This function
>   * also gets called if I2C encounters any errors.
> @@ -221,14 +269,36 @@ static int i2c_davinci_wait_bus_not_busy(struct 
> davinci_i2c_dev *dev,
>                      char allow_sleep)
> {
>     unsigned long timeout;
> +    u16 i;
> +    static u16 to_cnt = 0;
> +    u32 flag = 0;
> 
>     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;
> +            & DAVINCI_I2C_STR_BB) {
> +
> +        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 if (cpu_is_davinci_dm644x() || cpu_is_davinci_dm355()) {
> +            to_cnt = 0;
> +            dev_err(dev->dev, "initiating i2c bus recovery\n");
> +            /* Send the NACK to the slave */
> +            flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_IMR_REG);
> +            flag |=  DAVINCI_I2C_MDR_NACK;
> +            /* write the data into mode register */
> +            davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
> +            /* Disable i2c */
> +            disable_i2c_pins();
> +            for (i = 0; i < 10; i++)
> +                pulse_i2c_clock();
> +            /* Re-enable i2c */
> +            enable_i2c_pins();
> +            i2c_davinci_init(dev);
>         }
>         if (allow_sleep)
>             schedule_timeout(1);
> @@ -309,7 +379,23 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct 
> i2c_msg *msg, int stop)
>     r = wait_for_completion_interruptible_timeout(&dev->cmd_complete,
>                               dev->adapter.timeout);
>     if (r == 0) {
> -        dev_err(dev->dev, "controller timed out\n");
> +        u16 i;
> +        u32 flag = 0;
> +        if (cpu_is_davinci_dm644x() || cpu_is_davinci_dm355()) {
> +            dev_err(dev->dev, "initiating i2c bus recovery\n");
> +            /* Send the NACK to the slave */
> +            flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_IMR_REG);
> +            flag |=  DAVINCI_I2C_MDR_NACK;
> +            /* write the data into mode register */
> +            davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
> +            /* Disable i2c */
> +            disable_i2c_pins();
> +            /* Send high and low on the SCL line */
> +            for (i = 0; i < 10; i++)
> +                pulse_i2c_clock();
> +            /* Re-enable i2c */
> +            enable_i2c_pins();
> +        }
>         i2c_davinci_init(dev);
>         dev->buf_len = 0;
>         return -ETIMEDOUT;
> -- 
> 1.6.3.3.MVISTA
> 
> 
> _______________________________________________
> 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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