Re: [PATCH V3 2/2] mmc: core: fix performance regression initializing MMC host controllers

Ulf Hansson
2013-04-08T09:41:10Z

On 5 April 2013 15:31, Adrian Hunter <adrian.hunter@intel.com> wrote:
> Commit fa5501890d8974301042e0202d342a6cbe8609f4 introduced a boot time
> performance regression by adding mmc_power_up() to mmc_start_host().
> mmc_power_up() is not necessary to host controller initialization, it is
> part of card initialization and is performed anyway asynchronously.
> Please see the original commit for an explanation of the use of
> mmc_power_up() in mmc_start_host().
>
> This patch allows a driver to leave the power up in asynchronous code
> (as it was before).
>
> On my current target platform this reduces driver initialization from:
>
> [ 1.313220] initcall sdhci_acpi_driver_init+0x0/0x12 returned 0 after 102008 usecs
>
> to this:
>
> [ 1.217209] initcall sdhci_acpi_driver_init+0x0/0x12 returned 0 after 8331 usecs
>
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
> drivers/mmc/core/core.c | 3 ++-
> drivers/mmc/host/sdhci-acpi.c | 2 ++
> include/linux/mmc/host.h | 1 +
> 3 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 3bf1c46..c1893c9 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2416,7 +2416,8 @@ void mmc_start_host(struct mmc_host *host)
> {
> host->f_init = max(freqs[0], host->f_min);
> host->rescan_disable = 0;
> - mmc_power_up(host);
> + if (!(host->caps2 & MMC_CAP2_NO_PRESCAN_POWERUP))
> + mmc_power_up(host);
> mmc_detect_change(host, 0);
> }
>
> diff --git a/drivers/mmc/host/sdhci-acpi.c b/drivers/mmc/host/sdhci-acpi.c
> index 2592ddd..7bcf74b 100644
> --- a/drivers/mmc/host/sdhci-acpi.c
> +++ b/drivers/mmc/host/sdhci-acpi.c
> @@ -195,6 +195,8 @@ static int sdhci_acpi_probe(struct platform_device *pdev)
> host->mmc->pm_caps |= c->slot->pm_caps;
> }
>
> + host->mmc->caps2 |= MMC_CAP2_NO_PRESCAN_POWERUP;
> +
> err = sdhci_add_host(host);
> if (err)
> goto err_free;
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 17d7148..8873e83 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -280,6 +280,7 @@ struct mmc_host {
> #define MMC_CAP2_PACKED_WR (1 << 13) /* Allow packed write */
> #define MMC_CAP2_PACKED_CMD (MMC_CAP2_PACKED_RD | \
> MMC_CAP2_PACKED_WR)
> +#define MMC_CAP2_NO_PRESCAN_POWERUP (1 << 14) /* Don't power up before scan */
>
> mmc_pm_flag_t pm_caps; /* supported pm features */
>
> --
> 1.7.11.7
> --
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Acked-by: Ulf Hansson <ulf.hansson@linaro.org>