On Fri, Nov 21, 2014 at 01:28:44AM +0400, Alexander Kochetkov wrote:
> Arbitration Lost is a expected situation in a multimaster environment.
> IP correctly detect it.
> 
> The only reason for reseting IP in the AL case is to be sure to
> avoid advisory 1.94 (omap3) and errata i595 (omap4):
> "I2C: After an Arbitration is Lost the Module Incorrectly Starts
> the Next Transfer" with workaround: "The MST and STT bits inside
> I2C_CON should be set to 1 at the same moment (avoid setting the
> MST bit to 1 while STT = 0)."
> 
> The driver never writes MST and STT bits separately and doesn't
> create condition for errata. So the reset is not necessary.
> 
> Tested on Beagleboard XM C.
> 
> Signed-off-by: Alexander Kochetkov <al.koc...@gmail.com>
> ---
>  drivers/i2c/busses/i2c-omap.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index 3ffb9c0..47103e7 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -707,13 +707,17 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap,
>               return 0;
>  
>       /* We have an error */
> -     if (dev->cmd_err & (OMAP_I2C_STAT_AL | OMAP_I2C_STAT_ROVR |
> +     if (dev->cmd_err & (OMAP_I2C_STAT_ROVR |
>                           OMAP_I2C_STAT_XUDF)) {
>               omap_i2c_reset(dev);
>               __omap_i2c_init(dev);
>               return -EIO;
>       }
>  
> +     if (dev->cmd_err & OMAP_I2C_STAT_AL) {
> +             return -EIO;
> +     }

The errno for AL is -EAGAIN. Curly braces are not needed.

> +
>       if (dev->cmd_err & OMAP_I2C_STAT_NACK) {
>               if (msg->flags & I2C_M_IGNORE_NAK)
>                       return 0;
> -- 
> 1.7.9.5
> 

Attachment: signature.asc
Description: Digital signature

Reply via email to