[PATCH 0/3] mmc: Wait for card_busy before starting sdio requests

[Doug Anderson]

Hi,

On Thu, Sep 24, 2015 at 2:19 AM, Hans de Goede <hdegoede at redhat.com> wrote:
> Hi,
>
> On 23-09-15 23:43, Ulf Hansson wrote:
>>
>> On 22 September 2015 at 17:30, Hans de Goede <hdegoede at redhat.com> wrote:
>>>
>>> Hi Ulf,
>>>
>>> Here is a non RFC version of my patch-set to wait for card_busy before
>>> starting sdio requests. It is the same as the RFC version of the set,
>>> but this time it has been tested no hardware which actually needs this
>>> and I can confirm now that this fixes wifi on that hardware.
>>
>>
>> Great! Thanks, applied for next!
>
>
> Great, thanks, I guess it is too late for this to go as a fix into
> 4.3-rcX (no worries if it is) ?
>
>>> This patch-set should also allow removing this dw_mmc specific fix:
>>>
>>>
>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/mmc/host/dw_mmc.c?id=0bdbd0e88cf6b603a2196418672715b0890fb040
>>>
>>> As this patch-set fixes this problem in a generic manner.
>>
>>
>> Care to send a patch to remove the above hack/fix?
>
>
> I do not have any hardware to test this.
>
> I've added Doug the original author of that patch to the Cc.
>
> Dough, can you test if with the patch set from this mail thread
> (merged into mmc/next) this patch:
>
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/mmc/host/dw_mmc.c?id=0bdbd0e88cf6b603a2196418672715b0890fb040
>
> Is still necessary ? Since this patch-set fixes the same issue
> in the mmc core I believe that this commit can be reverted now.

I'll try to find some time in the next few days to test, but I'm not
terribly hopeful we can just revert the patch because:

1. Only one of the two callers of dw_mci_wait_while_busy() is handled
by your patch.  mci_send_cmd() is used internally in dw_mmc to throw
something in the CMD register without going through the normal MMC
path.  This is used exclusively to update the clock registers in
dw_mmc.  I'm pretty sure this needs the wait, too.  It's always seemed
weird / awkward to me that you need to use the CMD register to update
clock settings in dw_mmc, but c'est la vie.

2. If I remember correctly, we ran into other instances where non-SDIO
cards needed the busy check.  It wasn't terribly common, but I think I
ran into this when stress testing, but only on a few cards.  The patch
referenced here only seems to check for SDIO commands.  As I
understand it, to be correct, it should check for all data commands
(other than stop or voltage change commands).  The Designware Databook
makes no reference to only needing the wait for SDIO commands.


...of course, it's always possible that some of the things I saw above
will no longer happen with all the other fixes we've done in the
meantime (turning on voltages at the right time, adding the right
delays, etc).


Note that I've hardly looked at sdhci at all, but on SDHCI is this
handled by the "SDHCI_DATA_INHIBIT" bits?


-Doug