mmc: core: fix performance regression initializing MMC host controllers
Commit fa5501890d8974301042e0202d342a6cbe8609f4 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>
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 @@
#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 */