Re: [PATCH V4 01/15] mmc: host: Add facility to support re-tuning

[Arend van Spriel <arend@broadcom.com>]

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).

> 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

Regards,
Arend