linux-kernel - Re: [PATCH] i2c: cadence: try reset when master receive error interrupts

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Date:   Fri, 15 Feb 2019 16:37:46 +0530
From:   Shubhrajyoti Datta <shubhrajyoti.datta@...il.com>
To:     sxauwsk <sxauwsk@....com>
Cc:     Michal Simek <michal.simek@...inx.com>,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
Subject: Re: [PATCH] i2c: cadence: try reset when master receive error interrupts

Hi Sxauwsk,

On Wed, Jan 30, 2019 at 3:13 PM sxauwsk <sxauwsk@....com> wrote:
>
> When the adapter receive error interrupts, such as NACK, arbitration lost,
> cdns_i2c_master_xfer return to the caller directly instead of resuming
> the adapter which resulted in the adapter being out of control.
>
> So when driver detect err_status then try to repair and fix it.
>
> Signed-off-by: sxauwsk <sxauwsk@....com>
> ---
>  drivers/i2c/busses/i2c-cadence.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
> index b13605718291..e10048d7524a 100644
> --- a/drivers/i2c/busses/i2c-cadence.c
> +++ b/drivers/i2c/busses/i2c-cadence.c
> @@ -548,10 +548,6 @@ static int cdns_i2c_process_msg(struct cdns_i2c *id, struct i2c_msg *msg,
>         cdns_i2c_writereg(CDNS_I2C_IXR_ALL_INTR_MASK,
>                           CDNS_I2C_IDR_OFFSET);
>
> -       /* If it is bus arbitration error, try again */
> -       if (id->err_status & CDNS_I2C_IXR_ARB_LOST)
> -               return -EAGAIN;
> -
>         return 0;
>  }
>
> @@ -617,13 +613,19 @@ static int cdns_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>                         id->bus_hold_flag = 0;
>
>                 ret = cdns_i2c_process_msg(id, msgs, adap);
> -               if (ret)
> +               if (!ret)
>                         goto out;
>
In case  the Arbitration error happend  the cdns_i2c_process_msg would return 0
and we will miss the check  below.

Am I missing something ?

>                 /* Report the other error interrupts to application */
>                 if (id->err_status) {
>                         cdns_i2c_master_reset(adap);
>
> +                       /* If it is bus arbitration error, try again */
> +                       if (id->err_status & CDNS_I2C_IXR_ARB_LOST) {
> +                               ret = -EAGAIN;
> +                               goto out;
> +                       }
> +
>                         if (id->err_status & CDNS_I2C_IXR_NACK) {
>                                 ret = -ENXIO;
>                                 goto out;
> --
> 2.19.2
>
>