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

From: [email-masked] (Adrian Hunter)
Date: Thu, 28 Apr 2016 10:04:34 +0300

On 24/04/16 13:47, Dong Aisheng wrote:
> On Fri, Apr 22, 2016 at 8:48 PM, Adrian Hunter <[email-masked]> 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?

Sure

> 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.

So let's not spend time on it.

> 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?

sdhci spin lock is unlocked while waiting for tuning commands.

> 
> Regards
> Dong Aisheng
> 
>>>
>>> CC: stable <[email-masked]>
>>> Signed-off-by: Dong Aisheng <[email-masked]>
>>> ---
>>>  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);
>>>  }
>>>
>>>
>>
>