[PATCH v10 6/6] mmc: core: Add support for resetting an eMMC at system resume

[Ulf Hansson]

The DT property reset-card-at-resume specifies that we need to make a reset
of an eMMC card at system resume, assuming it also has stayed powered on
during system suspend.

To implement support for this, let's start by parsing for the new DT
property and set the new bit MMC_CAP2_RESET_AT_RESUME if it's found. Based
on the property, we must also set MMC_PM_KEEP_POWER in the pm_flags for the
host, to keep the eMMC powered on during system suspend.

Finally, to manage the actual reset during system resume, let's extend
mmc_resume() to support the needed behaviour.

Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxxxxxxxx>
---
 drivers/mmc/core/host.c  | 10 ++++++++++
 drivers/mmc/core/mmc.c   |  5 +++++
 include/linux/mmc/host.h |  1 +
 3 files changed, 16 insertions(+)

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 8e9e61839198..e3daf4026cba 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -48,6 +48,14 @@ static int mmc_host_class_prepare(struct device *dev)
 	if (host->bus_ops->pre_suspend)
 		return host->bus_ops->pre_suspend(host);
 
+	/*
+	 * If it's required to make a reset of the card at system resume, this
+	 * indirectly also means that we must keep the card powered on during
+	 * system suspend.
+	 */
+	if (host->caps2 & MMC_CAP2_RESET_AT_RESUME)
+		return mmc_set_host_pm_flags(host, MMC_PM_KEEP_POWER);
+
 	return 0;
 }
 
@@ -375,6 +383,8 @@ int mmc_of_parse(struct mmc_host *host)
 		host->pm_caps |= MMC_PM_KEEP_POWER;
 	if (device_property_read_bool(dev, "wakeup-source"))
 		host->pm_caps |= MMC_PM_WAKE_SDIO_IRQ;
+	if (device_property_read_bool(dev, "reset-card-at-resume"))
+		host->caps2 |= MMC_CAP2_RESET_AT_RESUME;
 	if (device_property_read_bool(dev, "mmc-ddr-3_3v"))
 		host->caps |= MMC_CAP_3_3V_DDR;
 	if (device_property_read_bool(dev, "mmc-ddr-1_8v"))
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index d4bf0f25bd74..908d5cad304b 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -2315,6 +2315,11 @@ static int mmc_resume(struct mmc_host *host)
 	}
 
 	pm_runtime_enable(&host->card->dev);
+
+	if (mmc_card_keep_power(host) &&
+	    host->caps2 & MMC_CAP2_RESET_AT_RESUME)
+		_mmc_hw_reset(host);
+
 	host->pm_flags &= ~MMC_PM_KEEP_POWER;
 	return 0;
 }
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 032c018650e0..552873da7987 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -430,6 +430,7 @@ struct mmc_host {
 	u32			caps2;		/* More host capabilities */
 
 #define MMC_CAP2_BOOTPART_NOACC	(1 << 0)	/* Boot partition no access */
+#define MMC_CAP2_RESET_AT_RESUME (1 << 1)	/* Reset the card at system resume */
 #define MMC_CAP2_FULL_PWR_CYCLE	(1 << 2)	/* Can do full power cycle */
 #define MMC_CAP2_FULL_PWR_CYCLE_IN_SUSPEND (1 << 3) /* Can do full power cycle in suspend */
 #define MMC_CAP2_HS200_1_8V_SDR	(1 << 5)        /* can support */
-- 
2.43.0