Re: [RFC] MMC-4.5 Power OFF Notify rework

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On Mon, Apr 2, 2012 at 10:47 AM, Saugata Das <saugata.das@xxxxxxxxxx> wrote:

>>> +       host->power_notify_type = MMC_HOST_PW_NOTIFY_LONG;
>>
>> This looks new, can you explain in the code as comments
>> or in the commit message when SHORT and LONG notifications are
>> used and why?
>>
>
> The mmc_poweroff_notify with MMC_HOST_PW_NOTIFY_LONG will take longer
> time  to complete than MMC_HOST_PW_NOTIFY_SHORT. So, the idea is that
> if we use mmc_poweroff_notify on suspend path, then we should use
> MMC_HOST_PW_NOTIFY_SHORT and if we use mmc_poweroff_notify from the
> shutdown path, then we should use MMC_HOST_PW_NOTIFY_LONG.
>
> We will add this in the description.

OK sounds good.

>>> @@ -1338,12 +1338,18 @@ static int mmc_suspend(struct mmc_host *host)
>>>        BUG_ON(!host->card);
>>>
>>>        mmc_claim_host(host);
>>> -       if (mmc_card_can_sleep(host)) {
>>> -               err = mmc_card_sleep(host);
>>> +       if (host->caps2 & MMC_CAP2_POWER_OFF_VCCQ_DURING_SUSPEND) {
>>> +               err = mmc_poweroff_notify(host);
>>>                if (!err)
>>> -                       mmc_card_set_sleep(host->card);
>>> -       } else if (!mmc_host_is_spi(host))
>>> +                       goto out;
>>> +       }
>>> +
>>> +       if (mmc_card_can_sleep(host))
>>> +               err = mmc_card_sleep(host);
>>> +       else if (!mmc_host_is_spi(host))
>>>                mmc_deselect_cards(host);
>>
>> Are you sure you should not deselect the card on an SPI host also if
>> you power off? (I'm just confused, better to ask...)
>>
>
> eMMC does not support SPI mode. So, the POWER OFF NOTIFY, which is an
> eMMC feature, can not be used on SPI mode. The above code (which you
> are referring) puts the eMMC to low power "standby" state with
> mmc_deselect_cards if sleep is not allowed. This logic has not been
> modified by the POWER OFF NOTIFY patch.

OK I would add a small comment above the else if (!mmc_host_is_spi(host))
such as /* SPI mode is only used external cards */ or so, it helsps when
reading the code.

Yours,
Linus Walleij
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