Re: [PATCH v1] i2c: imx: Retry transfer on transient failure

[Francesco Dolcini <francesco.dolcini@toradex.com>]

Hello Marco

On Tue, Jul 12, 2022 at 10:47:16AM +0200, Marco Felsch wrote:
> On 22-07-12, Francesco Dolcini wrote:
> > From: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
> > 
> > Set the i2c_adapter retries field to a sensible value. This allows
> > the i2c core to retry master_xfer()/master_xfer_atomic() when it
> > returns -EAGAIN. Currently the i2c-imx driver returns -EAGAIN only
> > on Tx arbitration failure (I2SR_IAL).
> > 
> > Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
> > Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
> > ---
> >  drivers/i2c/busses/i2c-imx.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> > index e9e2db68b9fb..26738e713c94 100644
> > --- a/drivers/i2c/busses/i2c-imx.c
> > +++ b/drivers/i2c/busses/i2c-imx.c
> > @@ -54,6 +54,7 @@
> >  #define DRIVER_NAME "imx-i2c"
> >  
> >  #define I2C_IMX_CHECK_DELAY 30000 /* Time to check for bus idle, in NS */
> > +#define I2C_IMX_MAX_RETRIES 3     /* Retries on arbitration loss */
> 
> Just one question: Why 3 and should we document this within the commit
> message?

In our tests 3 seems big enough to solve some sporadic failure we
experienced, and small enough to not have any kind of drawback. This is
the meaning of "sensible" value I have in the commit message, other
drivers use the same value.

Francesco