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);
> + 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);
> + 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
> + 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.
> +}
> +
> 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
> + 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
> + err = mmc_sd_resume(host);
> + if (err)
> + pr_err("%s: error %d doing aggessive resume\n",
> + mmc_hostname(host), err);
> +
> + return err;
As above
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.
> #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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