On 13/04/15 15:30, Ulf Hansson wrote: > On 2 April 2015 at 18:18, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >> On 2/04/2015 4:05 p.m., Ulf Hansson wrote: >>> >>> [...] >>> >>>>> >>>>>> - ability to enable / disable re-tuning >>>>> >>>>> >>>>> Handled internally by the mmc core. >>>> >>>> >>>> The host controller driver enables re-tuning based on whether the host >>>> controller requires it for that transfer mode. For example, only the >>>> SDHCI >>>> host controller knows if tuning is required for SDR50 mode according to >>>> the >>>> SDHCI capability register bit 45. >>> >>> >>> That seems a bit silly. >>> >>> All hosts wants the re-tuning to be "enabled" if the current used >>> speed mode requires it. It's not a host driver thing to deal with, >>> just the core. >> >> >> No it is up to the host controller. That is how it is in the >> SD Host Controller Specification. Both whether to tune SDR50 and >> whether to run a re-tuning timer. >> >> Tuning is inherently a host controller problem. The card can always >> receive correctly from the host, but the host has to adjust its >> "sampling point" to receive from the card. Only the host knows its >> capabilities in this regard. > > The requirement of doing re-tuning is stated in the eMMC/SD specs. The > SDHCI spec is just adopting to what these specs already states. Then, > I think the mmc core is the only one, who shall be able of > enable/disable re-tuning and thus we shouldn't need any APIs for that. > > Hosts needs to be able to flag that re-tuning is needed and to > configure the re-tuning timeout (optional). OK sent patch set V5 -- 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
