On 2 December 2014 at 13:28, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: > On 02/12/14 13:20, Ulf Hansson wrote: >> On 2 December 2014 at 11:08, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >>> On 02/12/14 11:35, Ulf Hansson wrote: >>>> On 1 December 2014 at 14:16, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >>>>> Re-tuning for HS400 mode must be done in HS200 >>>>> mode. Currently there is no support for that. >>>>> That needs to be reflected in the code. >>>>> Specifically, if tuning is executed in HS400 mode >>>>> then return an error, and if the re-tuning timer >>>>> is running when switching to HS400 mode, then >>>>> disable the timer. >>>>> >>>>> Note that periodic re-tuning is not expected >>>>> to be needed for HS400 but re-tuning is still >>>>> needed after the host controller has lost power. >>>> >>>> Why can't the old values be restored instead of trigger a re-tuning? >>> >>> The "values" (not sure what you mean by that) are not available to the >>> driver. Even if they were the operating conditions may have changed, (i.e. >>> temperature change) so the old "values" could still be wrong. >> >> The "values" I refer to is those which we "calculated" during the >> tuning process. >> >> What I had in mind, was that we should save these values at runtime PM >> suspend. And restore them at runtime PM resume. For some mmc >> controllers the "values" are typically just a some bits in a >> controller register, but that might not be true for all cases. >> >> Regarding the temperature change, etc. I think that is what the >> periodic retuning should be taken care off. >> >> Could you elaborate on why the "values" is not available to the driver? > > The "optimal sampling point" has no corresponding register or value > in SDHCI. Is that really the case for all sdhci variants? For sure I am not an sdhci expert, but I just find it to be a very poor HW design. Especially if the sdhci controller may lose power frequently, it will add a significant latency for each runtime PM resume cycle, right!? Anyway, thanks for sharing the information. 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
