[PATCH 10/23] mmc: core: disable auto retune during card detection process

[Dong Aisheng]

On Fri, Apr 22, 2016 at 8:48 PM, Adrian Hunter <adrian.hunter at intel.com> wrote:
> On 15/04/16 20:29, Dong Aisheng wrote:
>> During card detection process, mmc core may sends commands
>> to detect if card is still exist in mmc_rescan for removable
>> card which may trigger mmc retuning process after a bit time
>> of runtime pm suspend.
>> Obviously this retuning process is meaningless for card remove
>> case, so we disable mmc_retune in mmc_detect_change() for it.
>> For card insert case, the mmc_retune will be enabled normally
>> in its card initialization process later in mmc_execute_tuning().
>> So disable it at first has no side effection.
>
> We don't assume that the card has been removed, which is why we send
> commands to find out if it is still there.  If it is still there, this
> change will have incorrectly disabled re-tuning.
>

Do you mean the 'fake' card remove interrupt like caused by glitch?
Yes, if that the card is still exist and re-tuning is wrongly disabled.

So we could re-enable re-tuning for this special case?
Something like:
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 41b1e76..e1990a8 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2607,6 +2607,8 @@ void mmc_rescan(struct work_struct *work)

        /* if there still is a card present, stop here */
        if (host->bus_ops != NULL) {
+               if (tuning_is_enabled_before())
+                       mmc_retune_enable(host);
                mmc_bus_put(host);
                goto out;
        }


> Do you have an actual problem with the way it works now?
>

No actual problems now.
I just observe a lot tuning commands keep sending although the card is already
removed which seems a bit meaningless.
And most tuning execution process is executed with sin_lock_irqsave, i'm not
sure if the mass tuning commands may affect the system when CPU is busy.
What do you think?

Regards
Dong Aisheng

>>
>> CC: stable <stable at vger.kernel.org>
>> Signed-off-by: Dong Aisheng <aisheng.dong at nxp.com>
>> ---
>>  drivers/mmc/core/core.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 52bfaf0..76d0802 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -1888,6 +1888,7 @@ static void _mmc_detect_change(struct mmc_host *host, unsigned long delay,
>>               pm_wakeup_event(mmc_dev(host), 5000);
>>
>>       host->detect_change = 1;
>> +     mmc_retune_disable(host);
>>       mmc_schedule_delayed_work(&host->detect, delay);
>>  }
>>
>>
>