Re: [PATCH V6 08/15] mmc: mmc: Hold re-tuning if the card is put to sleep

[Adrian Hunter <adrian.hunter@intel.com>]

On 04/05/15 16:44, Ulf Hansson wrote:
> On 20 April 2015 at 14:09, Adrian Hunter <adrian.hunter@intel.com> wrote:
>> Currently "mmc sleep" is used before power off and
>> is not paired with waking up. Nevertheless hold
>> re-tuning.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>> ---
>>  drivers/mmc/core/mmc.c | 14 +++++++++++---
>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>> index f36c76f..daf9954 100644
>> --- a/drivers/mmc/core/mmc.c
>> +++ b/drivers/mmc/core/mmc.c
>> @@ -21,6 +21,7 @@
>>  #include <linux/mmc/mmc.h>
>>
>>  #include "core.h"
>> +#include "host.h"
>>  #include "bus.h"
>>  #include "mmc_ops.h"
>>  #include "sd_ops.h"
>> @@ -1504,6 +1505,7 @@ static int mmc_can_sleep(struct mmc_card *card)
>>         return (card && card->ext_csd.rev >= 3);
>>  }
>>
>> +/* If necessary, callers must hold re-tuning */
> 
> Remove this comment.
> 
>>  static int mmc_sleep(struct mmc_host *host)
>>  {
>>         struct mmc_command cmd = {0};
>> @@ -1631,6 +1633,7 @@ static int _mmc_suspend(struct mmc_host *host, bool is_suspend)
>>         int err = 0;
>>         unsigned int notify_type = is_suspend ? EXT_CSD_POWER_OFF_SHORT :
>>                                         EXT_CSD_POWER_OFF_LONG;
>> +       bool retune_release = false;
>>
>>         BUG_ON(!host);
>>         BUG_ON(!host->card);
>> @@ -1651,17 +1654,22 @@ static int _mmc_suspend(struct mmc_host *host, bool is_suspend)
>>                 goto out;
>>
>>         if (mmc_can_poweroff_notify(host->card) &&
>> -               ((host->caps2 & MMC_CAP2_FULL_PWR_CYCLE) || !is_suspend))
>> +               ((host->caps2 & MMC_CAP2_FULL_PWR_CYCLE) || !is_suspend)) {
>>                 err = mmc_poweroff_notify(host->card, notify_type);
>> -       else if (mmc_can_sleep(host->card))
>> +       } else if (mmc_can_sleep(host->card)) {
>> +               mmc_retune_hold(host);
>>                 err = mmc_sleep(host);
>> -       else if (!mmc_host_is_spi(host))
>> +       } else if (!mmc_host_is_spi(host)) {
>>                 err = mmc_deselect_cards(host);
>> +       }
>>
>>         if (!err) {
>>                 mmc_power_off(host);
>>                 mmc_card_set_suspended(host->card);
>>         }
>> +
>> +       if (retune_release)
>> +               mmc_retune_release(host);
>>  out:
>>         mmc_release_host(host);
>>         return err;
> 
> Instead of add mmc_retune_hold|release() to _mmc_suspend(), I would
> like you to move that handling into mmc_sleep(). The code should be
> easier and it becomes more clear that it's because of a command
> sequence.
> 
> I think mmc_retune_hold() should be invoked before mmc_wait_for_cmd()
> and then mmc_retune_release() just after, in mmc_sleep(). That should
> work, right!?

That would be the same as holding re-tuning for that request, which is
what already happens i.e. adding hold()/release() around mmc_wait_for_cmd()
is redundant.

The options for the caller are:

1)
	hold re-tuning
	put emmc to sleep
	later wake up emmc
	release re-tuning

2)
	put emmc to sleep
	later increment hold_count
	wake up emmc ignoring CRC errors
	release re-tuning

But there is no wake-up function and the suspend path is using an unbalanced
mmc_sleep i.e. no corresponding wake up.

So that leaves what is happening now i.e. a comment plus explicit
hold()/release() in _mmc_suspend() so that future changes to _mmc_suspend()
know to take mmc_sleep re-tuning requirements into account.