On 2 May 2013 12:38, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> On 16/04/13 13:00, Ulf Hansson wrote:
>> Aggressive power management is suitable when saving power is
>> essential. At request inactivity timeout, aka pm runtime
>> autosuspend timeout, the card will be suspended.
>>
>> Once a new request arrives, the card will be re-initalized and
>> thus the first request will suffer from a latency. This latency
>> is card-specific, experiments has shown in general that SD-cards
>> has quite poor initialization time, around 300ms-1100ms. eMMC is
>> not surprisingly far better but still a couple of hundreds of ms
>> has been observed.
>>
>> Except for the request latency, it is important to know that
>> suspending the card will also prevent the card from executing
>> internal house-keeping operations in idle mode. This could mean
>> degradation in performance.
>>
>> To use this feature make sure the request inactivity timeout is
>> chosen carefully. This has not been done as a part of this patch.
>>
>> Enable this feature by using host cap MMC_CAP_AGGRESSIVE_PM and
>> by setting CONFIG_MMC_UNSAFE_RESUME.
>>
>> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>> Cc: Maya Erez <merez@xxxxxxxxxxxxxx>
>> Cc: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
>> Cc: Arnd Bergmann <arnd@xxxxxxxx>
>> Cc: Kevin Liu <kliu5@xxxxxxxxxxx>
>> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>> Cc: Daniel Drake <dsd@xxxxxxxxxx>
>> Cc: Ohad Ben-Cohen <ohad@xxxxxxxxxx>
>> ---
>> drivers/mmc/core/mmc.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>> drivers/mmc/core/sd.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>> include/linux/mmc/host.h | 2 +-
>> 3 files changed, 86 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>> index bf19058..8dfbc84 100644
>> --- a/drivers/mmc/core/mmc.c
>> +++ b/drivers/mmc/core/mmc.c
>> @@ -1454,6 +1454,47 @@ static int mmc_resume(struct mmc_host *host)
>> return err;
>> }
>>
>> +
>> +/*
>> + * Callback for runtime_suspend.
>> + */
>> +static int mmc_runtime_suspend(struct mmc_host *host)
>> +{
>> + int err;
>> +
>> + if (!(host->caps & MMC_CAP_AGGRESSIVE_PM))
>> + return 0;
>> +
>
> mmc_power_off() needs to be within mmc_claim_host() / mmc_release_host().
>
> Claiming is nested, so you can out put mmc_claim_host() here:
>
> mmc_claim_host(host);
OK
>
>
>> + err = mmc_suspend(host);
>> + if (err) {
>> + pr_err("%s: error %d doing aggessive suspend\n",
>> + mmc_hostname(host), err);
>> + return err;
>
> goto out;
>
>> + }
>> +
>> + mmc_power_off(host);
>
> out:
> mmc_release_host(host);
>
OK
>> + return err;
>> +}
>> +
>> +/*
>> + * Callback for runtime_resume.
>> + */
>> +static int mmc_runtime_resume(struct mmc_host *host)
>> +{
>> + int err;
>> +
>> + if (!(host->caps & MMC_CAP_AGGRESSIVE_PM))
>> + return 0;
>> +
>> + mmc_power_up(host);
>
> As above
>
OK
>> + err = mmc_resume(host);
>> + if (err)
>> + pr_err("%s: error %d doing aggessive resume\n",
>> + mmc_hostname(host), err);
>> +
>> + return err;
>
> The power is on - leaving the device in a RPM_SUSPENDED state does not seem
> useful so better to return zero here.
OK
>
>> +}
>> +
>> static int mmc_power_restore(struct mmc_host *host)
>> {
>> int ret;
>> @@ -1514,6 +1555,8 @@ static const struct mmc_bus_ops mmc_ops_unsafe = {
>> .detect = mmc_detect,
>> .suspend = mmc_suspend,
>> .resume = mmc_resume,
>> + .runtime_suspend = mmc_runtime_suspend,
>> + .runtime_resume = mmc_runtime_resume,
>> .power_restore = mmc_power_restore,
>> .alive = mmc_alive,
>> };
>> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
>> index 30387d6..e0458f9 100644
>> --- a/drivers/mmc/core/sd.c
>> +++ b/drivers/mmc/core/sd.c
>> @@ -1095,6 +1095,46 @@ static int mmc_sd_resume(struct mmc_host *host)
>> return err;
>> }
>>
>> +/*
>> + * Callback for runtime_suspend.
>> + */
>> +static int mmc_sd_runtime_suspend(struct mmc_host *host)
>> +{
>> + int err;
>> +
>> + if (!(host->caps & MMC_CAP_AGGRESSIVE_PM))
>> + return 0;
>> +
>> + err = mmc_sd_suspend(host);
>> + if (err) {
>> + pr_err("%s: error %d doing aggessive suspend\n",
>> + mmc_hostname(host), err);
>> + return err;
>> + }
>> +
>> + mmc_power_off(host);
>
> As above
OK
>
>> + return err;
>> +}
>> +
>> +/*
>> + * Callback for runtime_resume.
>> + */
>> +static int mmc_sd_runtime_resume(struct mmc_host *host)
>> +{
>> + int err;
>> +
>> + if (!(host->caps & MMC_CAP_AGGRESSIVE_PM))
>> + return 0;
>> +
>> + mmc_power_up(host);
>
> As above
OK
>
>> + err = mmc_sd_resume(host);
>> + if (err)
>> + pr_err("%s: error %d doing aggessive resume\n",
>> + mmc_hostname(host), err);
>> +
>> + return err;
>
> As above
OK
>
> return 0
>
>> +}
>> +
>> static int mmc_sd_power_restore(struct mmc_host *host)
>> {
>> int ret;
>> @@ -1119,6 +1159,8 @@ static const struct mmc_bus_ops mmc_sd_ops = {
>> static const struct mmc_bus_ops mmc_sd_ops_unsafe = {
>> .remove = mmc_sd_remove,
>> .detect = mmc_sd_detect,
>> + .runtime_suspend = mmc_sd_runtime_suspend,
>> + .runtime_resume = mmc_sd_runtime_resume,
>> .suspend = mmc_sd_suspend,
>> .resume = mmc_sd_resume,
>> .power_restore = mmc_sd_power_restore,
>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
>> index 17d7148..cec6684 100644
>> --- a/include/linux/mmc/host.h
>> +++ b/include/linux/mmc/host.h
>> @@ -239,7 +239,7 @@ struct mmc_host {
>> #define MMC_CAP_SPI (1 << 4) /* Talks only SPI protocols */
>> #define MMC_CAP_NEEDS_POLL (1 << 5) /* Needs polling for card-detection */
>> #define MMC_CAP_8_BIT_DATA (1 << 6) /* Can the host do 8 bit transfers */
>> -
>> +#define MMC_CAP_AGGRESSIVE_PM (1 << 7) /* Suspend (e)MMC/SD at idle */
>
> Using a "cap" is not ideal here - it should really be under the control of
> user space.
Several other caps could be debated whether these should exist here as
well, but let's leave that to a separate discussion.
Until there are a solution for how to add new mmc features per host,
which should be runtime configurable, I believe this is the only way
we can do it.
Do note, that runtime pm can be disabled from user space, which
indirectly will prevent this feature from being used.
>
>> #define MMC_CAP_NONREMOVABLE (1 << 8) /* Nonremovable e.g. eMMC */
>> #define MMC_CAP_WAIT_WHILE_BUSY (1 << 9) /* Waits while card is busy */
>> #define MMC_CAP_ERASE (1 << 10) /* Allow erase/trim commands */
>>
>
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