Re: [PATCH] i2c: imx: increase retries on arbitration loss

[Primoz Fiser]

Hi Marco,

On 16. 12. 22 10:45, Marco Felsch wrote:
> Hi Primoz,
>
> On 22-12-16, Primoz Fiser wrote:
> > By default, retries value is set to 0 (no retries). Set retries to more
> > sensible value of 3 to allow i2c core to re-attempt transfer in case of
> > i2c arbitration loss (i2c-imx returns -EAGAIN errno is such case).
>
> apart the fact that the number of retries vary a lot and so the client
> driver behaviour can vary a lot which is not good IMHO, why do you think
> that 3 is a sufficient number?

IMHO it is better than leaving it at 0 (no retries)?

Setting it to sensible value like 3 will at least attempt to make 
transfer in case arbitration-loss occurs.

> If an arbitration loss happen, why do you think that retrying it 3 times
> changes that?

I our case, setting retries to non-zero value solves issues with PMIC 
shutdown on phyboard-mira which in some rare cases fails with "Failed to
shutdown (err =  -11)" (-EAGAIN).

To me it makes common sense retries is set to non-zero value especially 
for such rare conditions/situations.

BR,
Primoz

> Regards,
>    Marco
>
>
> > Signed-off-by: Primoz Fiser <primoz.fiser@xxxxxxxxx>
> > ---
> >   drivers/i2c/busses/i2c-imx.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> > index cf5bacf3a488..6a5694cfe1cc 100644
> > --- a/drivers/i2c/busses/i2c-imx.c
> > +++ b/drivers/i2c/busses/i2c-imx.c
> > @@ -1478,6 +1478,7 @@ static int i2c_imx_probe(struct platform_device *pdev)
> >   	i2c_imx->adapter.dev.parent	= &pdev->dev;
> >   	i2c_imx->adapter.nr		= pdev->id;
> >   	i2c_imx->adapter.dev.of_node	= pdev->dev.of_node;
> > +	i2c_imx->adapter.retries	= 3;
> >   	i2c_imx->base			= base;
> >   	ACPI_COMPANION_SET(&i2c_imx->adapter.dev, ACPI_COMPANION(&pdev->dev));
> >   
> > --
> > 2.25.1