On Fri, Dec 16, 2022 at 01:23:29PM +0100, Primoz Fiser wrote: > Hi all, > > On 16. 12. 22 12:13, Uwe Kleine-König wrote: > > On Fri, Dec 16, 2022 at 12:02:27PM +0100, Oleksij Rempel wrote: > > > On Fri, Dec 16, 2022 at 11:41:08AM +0100, Primoz Fiser wrote: > > > > 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. > > > > > > https://lore.kernel.org/all/Ys1bw9zuIwWS+bqw@shikoro/ > > Ohh I see. > > Reading through the thread I guess we aren't getting this mainlined at all > :) > > The only solid point in the thread seems to be that in that case we are not > covering up the potential i2c hardware issues? I believe that in this case we should just have a warning in the kernel. The retry potentially work-around a transient issue and we do not hide any hardware issue at the same time. It seems an easy win-win solution. > Yeah fair point but on the other hand, goal of this patch would be to > improve robustness in case of otherwise good performing hardware. From user > perspective I just want it to work despite it retrying under the hood from > time to time. I think Francesco had the same idea. Unfortunately I was missing the exact background that made us do this change, we just had it sitting in our fork for too long :-/ This is one of the reason I gave up on it. Quoting Uwe [1] > sometimes there is no practical way around such work arounds. I happens > from time to time that the reason for problem is known, but fixing the > hardware is no option, then you need such workrounds. (This applies to > both, retrying the transfers and resetting the bus.) Francesco [1] https://lore.kernel.org/all/20220715083400.q226rrwxsgt4eomp@xxxxxxxxxxxxxx/
