mmc: core: Prevent eMMC VCC supply to be cut from late init

For eMMC cards that has been initialized from a bootloader,
the VCC voltage supply must not be cut in an uncontrolled
manner, without first sending SLEEP or POWEROFF_NOTIFY.

The regulator_init_complete late initcall, may cut the VCC
regulator if it's reference counter is zero. To be able to
prevent the regulator from being cut, mmc_start_host, which
should execute at device init and thus before late init,
calls mmc_power_up. Then the host driver is able to increase
the reference to the regulator.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 15 insertions, 3 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index ba821fe70bc..0b6141d29db 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -42,6 +42,7 @@
 #include "sdio_ops.h"
 
 static struct workqueue_struct *workqueue;
+static const unsigned freqs[] = { 400000, 300000, 200000, 100000 };
 
 /*
  * Enabling software CRCs on the data blocks can be a significant (30%)
@@ -1157,6 +1158,9 @@ static void mmc_power_up(struct mmc_host *host)
 {
         int bit;
 
+        if (host->ios.power_mode == MMC_POWER_ON)
+                return;
+
         mmc_host_clk_hold(host);
 
         /* If ocr is set, we use it */
@@ -1199,6 +1203,10 @@ static void mmc_power_up(struct mmc_host *host)
 void mmc_power_off(struct mmc_host *host)
 {
         int err = 0;
+
+        if (host->ios.power_mode == MMC_POWER_OFF)
+                return;
+
         mmc_host_clk_hold(host);
 
         host->ios.clock = 0;
@@ -2005,7 +2013,6 @@ EXPORT_SYMBOL(mmc_detect_card_removed);
 
 void mmc_rescan(struct work_struct *work)
 {
-        static const unsigned freqs[] = { 400000, 300000, 200000, 100000 };
         struct mmc_host *host =
                 container_of(work, struct mmc_host, detect.work);
         int i;
@@ -2044,8 +2051,12 @@ void mmc_rescan(struct work_struct *work)
          */
         mmc_bus_put(host);
 
-        if (host->ops->get_cd && host->ops->get_cd(host) == 0)
+        if (host->ops->get_cd && host->ops->get_cd(host) == 0) {
+                mmc_claim_host(host);
+                mmc_power_off(host);
+                mmc_release_host(host);
                 goto out;
+        }
 
         mmc_claim_host(host);
         for (i = 0; i < ARRAY_SIZE(freqs); i++) {
@@ -2063,7 +2074,8 @@ void mmc_rescan(struct work_struct *work)
 
 void mmc_start_host(struct mmc_host *host)
 {
-        mmc_power_off(host);
+        host->f_init = max(freqs[0], host->f_min);
+        mmc_power_up(host);
         mmc_detect_change(host, 0);
 }