Re: [PATCH V2 3/3] mmc: dw_mmc: Dont cut off vqmmc and vmmc

Ulf Hansson
2014-08-28T07:25:56Z

On 27 August 2014 17:52, Doug Anderson <dianders@google.com> wrote:
> Ulf,
>
> On Wed, Aug 27, 2014 at 4:17 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>> Now, we've got MMC_CAP_NEEDS_POLL, so dw_mmc will periodically be
>>> called to check the card detect line, but with vmmc and vqmmc off. It
>>> will be unable to return a sensible value without actually turning on
>>> vmmc and vqmmc.
>>
>> Currently MMC_CAP_NEEDS_POLL mean the mmc rescan work will reschedule
>> itself with HZ interval. This to check for card insert/removal.
>>
>> Now, mmc_rescan() will, if present, invoke host's ->get_cd() callback
>> to check whether it's worth to continue initialization sequence or if
>> it should re-schedule itself again.
>>
>> If your host driver can distinguish whether a card is inserted, which
>> in this case are when vccq is turned off, your ->get_cd() callback need
>> to return 1. That will allow mmc_rescan() to continue it's
>> initialization sequence and do mmc_power_up().
>
> As per my other email, we can't tell whether a card is inserted when
> vqmmc is off.

I understand.

The solution I proposed above, is:

1) Enable MMC_CAP_NEEDS_POLL.
2) Make ->get_cd() return 1, when you can't distinguish if the card is inserted.

That will solve this issue and without messing up the mmc core.

>
> Does this mean that you have removed your objections to a solution
> like Yuvaraj has posted? We still need to break it into two patches
> (the core part and the dwmmc part), but otherwise is it OK? I can
> post the original patch I sent Yuvaraj if it's helpful (or he can just
> include my patch as part 1 of his series).

No. This can entirely be fixed in the host driver. As suggested above.

Kind regards
Uffe