[PATCH v2 3/3] mmc: core: Add power-off-delay-us support

[Judith Mendez]

Add support for power-off-delay-us which shall be used to specify
value of delay after deasserting power during MMC power cycles.
Default for delay is 1000us but custom delay can be passed in to work
around hardware issues such as slow RC discharge on MMC VDD rails.

Signed-off-by: Judith Mendez <jm@xxxxxx>
---
Changes since v1:
- Move delay to mmc_power_off
- Fix dt checks and remove print
- Move from mmc_host struct to mmc_ios struct
- Rename post-power-off-delay-ms to power_off_delay_us
---
 drivers/mmc/core/core.c  | 2 +-
 drivers/mmc/core/host.c  | 8 ++++++++
 include/linux/mmc/host.h | 1 +
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 29e80e5f928e9..9472041fe1c20 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1388,7 +1388,7 @@ void mmc_power_off(struct mmc_host *host)
 	 * XO-1.5, require a short delay after poweroff before the card
 	 * can be successfully turned on again.
 	 */
-	mmc_delay(1);
+	mmc_delay_us(host->ios.power_off_delay_us);
 }
 
 void mmc_power_cycle(struct mmc_host *host, u32 ocr)
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index b7ce3137d4529..fac50a2860211 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -421,6 +421,13 @@ int mmc_of_parse(struct mmc_host *host)
 	device_property_read_u32(dev, "post-power-on-delay-ms",
 				 &host->ios.power_delay_ms);
 
+	device_property_read_u32(dev, "power-off-delay-us",
+				 &host->ios.power_off_delay_us);
+	if (host->ios.power_off_delay_us < 1)
+		host->ios.power_off_delay_us = 1000;
+	if (host->ios.power_off_delay_us > 10000000)
+		host->ios.power_off_delay_us = 10000000;
+
 	return mmc_pwrseq_alloc(host);
 }
 
@@ -574,6 +581,7 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 
 	host->fixed_drv_type = -EINVAL;
 	host->ios.power_delay_ms = 10;
+	host->ios.power_off_delay_us = 1000;
 	host->ios.power_mode = MMC_POWER_UNDEFINED;
 
 	return host;
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index ba84f02c2a101..714417466707c 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -23,6 +23,7 @@ struct mmc_ios {
 	unsigned int	clock;			/* clock rate */
 	unsigned short	vdd;
 	unsigned int	power_delay_ms;		/* waiting for stable power */
+	unsigned int	power_off_delay_us;	/* waiting for power discharge */
 
 /* vdd stores the bit number of the selected voltage range from below. */
 
-- 
2.54.0