On 02/04/15 15:27, Arend van Spriel wrote: > On 04/02/15 14:25, Ulf Hansson wrote: >> On 2 April 2015 at 14:18, Adrian Hunter<adrian.hunter@xxxxxxxxx> wrote: >>> On 02/04/15 15:10, Ulf Hansson wrote: >>>> On 2 April 2015 at 12:30, Arend van Spriel<arend@xxxxxxxxxxxx> wrote: >>>>> On 04/02/15 10:43, Ulf Hansson wrote: >>>>>> >>>>>> [...] >>>>>>>>>> >>>>>>>>>> - ability to hold off re-tuning if the card is busy >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> What do you mean by "card is busy"? >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> I guess, more accurately, any time the card is in a state that is >>>>>>>> incapable >>>>>>>> of supporting re-tuning. For example: >>>>>>>> - DAT0 busy >>>>>>> >>>>>>> >>>>>>> >>>>>>> This state is not specific to re-tuning. An SDIO device can keep DAT0 >>>>>>> busy >>>>>>> at which the host controller can not start another request. >>>>>> >>>>>> >>>>>> Not entirely true. Some commands are allowed during this period, for >>>>>> example CMD13 (which doesn't exist for SDIO) >>>>> >>>>> >>>>> Yeah. I was wondering whether to mention that. >>>>> >>>>>> Anyway, I get the point. Thanks! >>>>>> >>>>>>> >>>>>>>> - between dependent commands like erase start, end, etc >>>>>>>> - card is asleep >>>>>>>> Also SDIO cards can have a custom sleep state where tuning won't work. >>>>>>> >>>>>>> >>>>>>> >>>>>>> Our SDIO wifi device has such a state and it can only come out of it >>>>>>> upon >>>>>>> CMD52 write or CMD14 (ExitSleep). >>>>>> >>>>>> >>>>>> So how will the mmc core know about these states? I guess we will >>>>>> require SDIO func drivers to deal with enable/disable or hold/release >>>>>> of re-tuning then? >>>>> >>>>> >>>>> This is actually why in the past we tried to only kick off retuning >>>>> before a >>>>> request that requires use of data line(s) so mmc core (or sdhci) would not >>>>> do re-tuning when SDIO func used CMD52 to wakeup the device. I never tried >>>>> CMD14 approach and not even sure from which spec it comes (maybe eMMC). >>>> >>>> That's an interesting idea. It would eliminate the need for SDIO func >>>> drivers to care about holding/releasing re-tuning. >>>> >>>> Would be nice to hear about Adrian's thoughts around this as well. >>> >>> I don't see how it would work because re-tuning is needed after the host >>> controller runtime resumes. i.e. once the SDIO wifi card stops being active >>> the host controller will runtime suspend. >> >> Why do we always need to re-tune from this phase? >> >> What Arend points out is that we could "delay" the re-tune until we >> know there is a DATA request. Wouldn't that work for SDHCI as well? > > You beat me to it, but that is indeed what I meant. The CMD line needs tuning too, so delaying tuning on every command will cause errors. It is better to hold tuning for the specific command used to wake-up. > > Regards, > Arend > >>> >>> Also I would expect doing re-tuning before every data request would likely >>> be unacceptable from a performance point of view. >>> >>>> >>>>> >>>>>> I don't like this, but if there is no other way... Also, we must be >>>>>> very careful on which API we exports for SDIO func drivers to use. The >>>>>> can easily be misinterpreted. >>>>>> >>>>>> [...] >>>> >>>> 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
