On 13 January 2015 at 14:23, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: > On 13/01/15 13:25, Ulf Hansson wrote: >> Hi Adrian, >> >> Thanks for working on this and apologize for my late reply! >> >> On 5 December 2014 at 18:41, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >>> Currently, there is core support for tuning during >>> initialization. There can also be a need to re-tune >>> periodically (e.g. sdhci) or to re-tune after the >>> host controller is powered off (e.g. after PM >>> runtime suspend / resume) or to re-tune in response >>> to CRC errors. >>> >>> The main requirements for re-tuning are: >>> - ability to enable /disable re-tuning >>> - ability to flag that re-tuning is needed >>> - ability to re-tune before any request >>> - ability to hold off re-tuning if the card is busy >>> - ability to hold off re-tuning if re-tuning is in >>> progress >>> - ability to run a re-tuning timer >> >> I suggest we skip the support for the re-tuning timer in this initial >> step and thus remove the related functionality from this patchset. It >> adds complexity, but more important it's not obvious that it actually >> will help. I am more concerned that it randomly will cause a request >> latency and thus decrease performance. >> >> The re-tuning period can't be selected "perfectly", so in this initial >> step let's instead just rely on re-tune from the request retry path. >> >> If we do see a need for a doing re-tuning periodically, how about >> using the runtime PM suspend path (of the mmc card device). In that >> way, we should be able to minimize the impact on performance. > > Thank you for looking at the patches. > > I am not sure I know what you mean. sdhci already has a re-tuning timer, so > this is just moving it into core, where it won't be used by other drivers > unless they enable it. I am kind of questioning the re-tuning timer in sdhci. What is it good for? Can sdhci rely on that the mmc core performs a re-tune from the request retry mechanism instead? > > I am not sure what you want to leave in sdhci.c and what you want in core, > if anything. We need all the infrastructure code in the core. Much like what your patchset does. Except that I would like you to remove the option of having a timer and the corresponding complexity it adds. > > At a minimum I need sdhci to be able to switch from hs400 to hs200, re-tune, > and switch back. As stated, I am only questioning the timer, nothing else. Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
