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

Primoz Fiser
2022-12-16T10:42:36Z

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@norik.com>
>> ---
>> 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
>>
>>
>>