RE: [PATCH v2] i2c: tegra: Add delay before reset the controller

[Alok Chauhan]

Hi all,

If there are no more concern then can we merge this patch to i2c tegra driver? 

Thanks
Alok

On Mon, Dec 26, 2011 at 4:44 PM, Alok Chauhan <alokc@xxxxxxxxxx> wrote:
> From: Alok Chauhan <alokc@xxxxxxxxxx>
>
> In NACK error condition, I2C controller violates clock-to-data setup 
> time before stop. In Software, because of this reset of controller is 
> happening before I2C controller could complete STOP condition.
>
> Added delay of 2 clock period before reset the controller in case of 
> NACK error.
>
> Signed-off-by: Alok Chauhan <alokc@xxxxxxxxxx>
> ---
> Instead of setting constant value for delay as was in previous patch, 
> now in the current modification delay will be calculated based on clock frequency of the bus.
>  drivers/i2c/busses/i2c-tegra.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-tegra.c 
> b/drivers/i2c/busses/i2c-tegra.c index 6381604..62e197c 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -517,6 +517,14 @@ static int tegra_i2c_xfer_msg(struct 
> tegra_i2c_dev *i2c_dev,
>        if (likely(i2c_dev->msg_err == I2C_ERR_NONE))
>                return 0;
>
> +       /*
> +        * In NACK error condition resetting of I2C controller happens
> +        * before STOP condition is properly completed by I2C 
> + controller,
> +        * so wait for 2 clock cycle to complete STOP condition.
> +        */

>>>>Why do you need to reset the controller in case of a NACK.
>>>This is required because of hardware limitations. Without reset we can't flus the internal hardware registers.


> +       if (i2c_dev->msg_err == I2C_ERR_NO_ACK)
> +               udelay(DIV_ROUND_UP(2 * 1000000, 
> + i2c_dev->bus_clk_rate));
> +
>        tegra_i2c_init(i2c_dev);
>        if (i2c_dev->msg_err == I2C_ERR_NO_ACK) {
>                if (msg->flags & I2C_M_IGNORE_NAK)
> --
> 1.7.4.1
>
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