mmc: core: Use MMC_UNSAFE_RESUME as default behavior

Invoking system suspend or shutdown without using the Kconfig option
MMC_UNSAFE_RESUME, did trigger an ungraceful power cut of the card.

To improve the situation, change the behavior to always make use of the
available bus_ops callbacks that handles system suspend and shutdown
properly.

By changing the behavior MMC_UNSAFE_RESUME becomes redundant, so lets's
remove it.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>

drivers/mmc/core/Kconfig

@@ -2,21 +2,6 @@
 # MMC core configuration
 #
 
-config MMC_UNSAFE_RESUME
-	bool "Assume MMC/SD cards are non-removable (DANGEROUS)"
-	help
-	  If you say Y here, the MMC layer will assume that all cards
-	  stayed in their respective slots during the suspend. The
-	  normal behaviour is to remove them at suspend and
-	  redetecting them at resume. Breaking this assumption will
-	  in most cases result in data corruption.
-
-	  This option is usually just for embedded systems which use
-	  a MMC/SD card for rootfs. Most people should say N here.
-
-	  This option sets a default which can be overridden by the
-	  module parameter "removable=0" or "removable=1".
-
 config MMC_CLKGATE
 	bool "MMC host clock gating"
 	help

drivers/mmc/core/core.c

@@ -64,23 +64,6 @@ static const unsigned freqs[] = { 400000, 300000, 200000, 100000 };
 bool use_spi_crc = 1;
 module_param(use_spi_crc, bool, 0);
 
-/*
- * We normally treat cards as removed during suspend if they are not
- * known to be on a non-removable bus, to avoid the risk of writing
- * back data to a different card after resume.  Allow this to be
- * overridden if necessary.
- */
-#ifdef CONFIG_MMC_UNSAFE_RESUME
-bool mmc_assume_removable;
-#else
-bool mmc_assume_removable = 1;
-#endif
-EXPORT_SYMBOL(mmc_assume_removable);
-module_param_named(removable, mmc_assume_removable, bool, 0644);
-MODULE_PARM_DESC(
-	removable,
-	"MMC/SD cards are removable and may be removed during suspend");
-
 /*
  * Internal function. Schedule delayed work in the MMC work queue.
  */

drivers/mmc/core/mmc.c

@@ -1634,16 +1634,6 @@ static int mmc_power_restore(struct mmc_host *host)
 }
 
 static const struct mmc_bus_ops mmc_ops = {
-	.remove = mmc_remove,
-	.detect = mmc_detect,
-	.suspend = NULL,
-	.resume = NULL,
-	.power_restore = mmc_power_restore,
-	.alive = mmc_alive,
-	.shutdown = mmc_shutdown,
-};
-
-static const struct mmc_bus_ops mmc_ops_unsafe = {
 	.remove = mmc_remove,
 	.detect = mmc_detect,
 	.suspend = mmc_suspend,
@@ -1655,17 +1645,6 @@ static const struct mmc_bus_ops mmc_ops_unsafe = {
 	.shutdown = mmc_shutdown,
 };
 
-static void mmc_attach_bus_ops(struct mmc_host *host)
-{
-	const struct mmc_bus_ops *bus_ops;
-
-	if (!mmc_card_is_removable(host))
-		bus_ops = &mmc_ops_unsafe;
-	else
-		bus_ops = &mmc_ops;
-	mmc_attach_bus(host, bus_ops);
-}
-
 /*
  * Starting point for MMC card init.
  */
@@ -1685,7 +1664,7 @@ int mmc_attach_mmc(struct mmc_host *host)
 	if (err)
 		return err;
 
-	mmc_attach_bus_ops(host);
+	mmc_attach_bus(host, &mmc_ops);
 	if (host->ocr_avail_mmc)
 		host->ocr_avail = host->ocr_avail_mmc;
 

drivers/mmc/core/sd.c

@@ -1207,16 +1207,6 @@ static int mmc_sd_power_restore(struct mmc_host *host)
 }
 
 static const struct mmc_bus_ops mmc_sd_ops = {
-	.remove = mmc_sd_remove,
-	.detect = mmc_sd_detect,
-	.suspend = NULL,
-	.resume = NULL,
-	.power_restore = mmc_sd_power_restore,
-	.alive = mmc_sd_alive,
-	.shutdown = mmc_sd_suspend,
-};
-
-static const struct mmc_bus_ops mmc_sd_ops_unsafe = {
 	.remove = mmc_sd_remove,
 	.detect = mmc_sd_detect,
 	.runtime_suspend = mmc_sd_runtime_suspend,
@@ -1228,17 +1218,6 @@ static const struct mmc_bus_ops mmc_sd_ops_unsafe = {
 	.shutdown = mmc_sd_suspend,
 };
 
-static void mmc_sd_attach_bus_ops(struct mmc_host *host)
-{
-	const struct mmc_bus_ops *bus_ops;
-
-	if (!mmc_card_is_removable(host))
-		bus_ops = &mmc_sd_ops_unsafe;
-	else
-		bus_ops = &mmc_sd_ops;
-	mmc_attach_bus(host, bus_ops);
-}
-
 /*
  * Starting point for SD card init.
  */
@@ -1254,7 +1233,7 @@ int mmc_attach_sd(struct mmc_host *host)
 	if (err)
 		return err;
 
-	mmc_sd_attach_bus_ops(host);
+	mmc_attach_bus(host, &mmc_sd_ops);
 	if (host->ocr_avail_sd)
 		host->ocr_avail = host->ocr_avail_sd;
 

include/linux/mmc/host.h

@@ -424,12 +424,9 @@ static inline int mmc_regulator_get_supply(struct mmc_host *mmc)
 
 int mmc_pm_notify(struct notifier_block *notify_block, unsigned long, void *);
 
-/* Module parameter */
-extern bool mmc_assume_removable;
-
 static inline int mmc_card_is_removable(struct mmc_host *host)
 {
-	return !(host->caps & MMC_CAP_NONREMOVABLE) && mmc_assume_removable;
+	return !(host->caps & MMC_CAP_NONREMOVABLE);
 }
 
 static inline int mmc_card_keep_power(struct mmc_host *host)