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. 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
