[PATCH v2] mfd: axp20x: Add a 500ms delay at the end of axp20x_power_off

[Hans de Goede]

The kernel expects the power_off function to not return, and if it does
it panics. Add a slight delay after the i2c write which turns off power
through the pmic, to give capacitors etc. some time to drain.

Without this the kernel lives on long enough after the poweroff to
print the following on the serial console on my Mele A1000G quad:

[  248.583588] reboot: Power down
[  248.600490] Kernel pa

With the delay the start of printing "Kernel panic" is gone.

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
Acked-by: Chen-Yu Tsai <wens at csie.org>
---
Changes in v2:
-Add Chen-Yu's Acked-by
-Fix spelling error in commit msg
---
 drivers/mfd/axp20x.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/mfd/axp20x.c b/drivers/mfd/axp20x.c
index 6364dab..fd80b09 100644
--- a/drivers/mfd/axp20x.c
+++ b/drivers/mfd/axp20x.c
@@ -17,6 +17,7 @@
  */
 
 #include <linux/err.h>
+#include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -677,6 +678,9 @@ static void axp20x_power_off(void)
 
 	regmap_write(axp20x_pm_power_off->regmap, AXP20X_OFF_CTRL,
 		     AXP20X_OFF);
+
+	/* Give capacitors etc. time to drain to avoid kernel panic msg. */
+	msleep(500);
 }
 
 int axp20x_match_device(struct axp20x_dev *axp20x)
-- 
2.7.4