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mmc: core: fix performance regression initializing MMC host controllers

Browse Source 
Commit fa5501890d introduced a 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.

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>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>
This commit is contained in:
Adrian Hunter 2013-04-04 16:41:06 +03:00 committed by Chris Ball
parent f9a94e0a3f
commit 0d3e3350d5
3 changed files with 5 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/mmc/core/core.c
View File

@ -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);
}

2
drivers/mmc/host/sdhci-acpi.c
View File

@ -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;

1
include/linux/mmc/host.h
View File

@ -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 */