mmc: add ability to save power by powering off cards

Power can be saved by powering off cards that are not in use.  This is
similar to suspend / resume except it is under the control of the driver,
and does not require any power management support.  It can only be used
when the driver can monitor whether the card is removed, otherwise it is
unsafe.  This is possible because, unlike suspend, the driver still
receives card detect and / or cover switch interrupts.

Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
Acked-by: Matt Fleming <matt@console-pimps.org>
Cc: Ian Molton <ian@mnementh.co.uk>
Cc: "Roberto A. Foglietta" <roberto.foglietta@gmail.com>
Cc: Jarkko Lavinen <jarkko.lavinen@nokia.com>
Cc: Denis Karpov <ext-denis.2.karpov@nokia.com>
Cc: Pierre Ossman <pierre@ossman.eu>
Cc: Philip Langdale <philipl@overt.org>
Cc: "Madhusudhan" <madhu.cr@ti.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 995db1853a8..27e842df6a6 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -549,6 +549,14 @@ static void mmc_resume(struct mmc_host *host)
 
 }
 
+static void mmc_power_restore(struct mmc_host *host)
+{
+        host->card->state &= ~MMC_STATE_HIGHSPEED;
+        mmc_claim_host(host);
+        mmc_init_card(host, host->ocr, host->card);
+        mmc_release_host(host);
+}
+
 #ifdef CONFIG_MMC_UNSAFE_RESUME
 
 static const struct mmc_bus_ops mmc_ops = {
@@ -556,6 +564,7 @@ static const struct mmc_bus_ops mmc_ops = {
         .detect = mmc_detect,
         .suspend = mmc_suspend,
         .resume = mmc_resume,
+        .power_restore = mmc_power_restore,
 };
 
 static void mmc_attach_bus_ops(struct mmc_host *host)
@@ -570,6 +579,7 @@ static const struct mmc_bus_ops mmc_ops = {
         .detect = mmc_detect,
         .suspend = NULL,
         .resume = NULL,
+        .power_restore = mmc_power_restore,
 };
 
 static const struct mmc_bus_ops mmc_ops_unsafe = {
@@ -577,6 +587,7 @@ static const struct mmc_bus_ops mmc_ops_unsafe = {
         .detect = mmc_detect,
         .suspend = mmc_suspend,
         .resume = mmc_resume,
+        .power_restore = mmc_power_restore,
 };
 
 static void mmc_attach_bus_ops(struct mmc_host *host)