[PATCH v2] mfd: tps65910: Correct power-off programming sequence

[Dmitry Osipenko <digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

This patch fixes system shutdown on a devices that use TPS65910 as a
system's power controller. In accordance to the TPS65910 datasheet, the
PMIC's state-machine transitions into the OFF state only when DEV_OFF
bit of DEVCTRL_REG is set. The ON / SLEEP states also should be cleared,
otherwise PMIC won't get into a proper state on shutdown. Devices like
Nexus 7 tablet and Ouya game console are now shutting down properly.

Tested-by: Zack Pearsall <zpearsall-/E1597aS9LQAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Dmitry Osipenko <digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---

Changelog:

v2: - Now using a single tps65910_reg_update_bits() instead of set+clear.
      Thanks to Michał Mirosław for the suggestion.

 drivers/mfd/tps65910.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/tps65910.c b/drivers/mfd/tps65910.c
index 11959021b50a..3f4483dec871 100644
--- a/drivers/mfd/tps65910.c
+++ b/drivers/mfd/tps65910.c
@@ -440,8 +440,13 @@ static void tps65910_power_off(void)
 			DEVCTRL_PWR_OFF_MASK) < 0)
 		return;
 
-	tps65910_reg_clear_bits(tps65910, TPS65910_DEVCTRL,
-			DEVCTRL_DEV_ON_MASK);
+	if (tps65910_reg_clear_bits(tps65910, TPS65910_DEVCTRL,
+			DEVCTRL_DEV_SLP_MASK) < 0)
+		return;
+
+	tps65910_reg_update_bits(tps65910, TPS65910_DEVCTRL,
+				 DEVCTRL_DEV_OFF_MASK | DEVCTRL_DEV_ON_MASK,
+				 DEVCTRL_DEV_OFF_MASK);
 }
 
 static int tps65910_i2c_probe(struct i2c_client *i2c,
-- 
2.26.0