[PATCH v4] mfd: tps65910: Correct power-off programming sequence

[Dmitry Osipenko <digetx@gmail.com>]

Correct power-off programming sequence in order to fix shutting down
devices which are using TPS65910 PMIC.

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 shutting down properly now.

Tested-by: Peter Geis <pgwipeout@gmail.com>
Tested-by: Zack Pearsall <zpearsall@yahoo.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---

Changelog:

v4: - Rebased on a recent linux-next.

v3: - Removed the DEV_SLP_MASK clearing and adding clarifying comment to
      the code about why clearing PWR_OFF bit needs to be done, which was
      suggested by  Michał Mirosław in a review comment to v2.

    - Added tested-by from Peter Geis who tested v3 on his Ouya game
      console.

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

 drivers/mfd/tps65910.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/tps65910.c b/drivers/mfd/tps65910.c
index ca0b61011def..6e105cca27d4 100644
--- a/drivers/mfd/tps65910.c
+++ b/drivers/mfd/tps65910.c
@@ -436,12 +436,18 @@ static void tps65910_power_off(void)
 
 	tps65910 = dev_get_drvdata(&tps65910_i2c_client->dev);
 
+	/*
+	 * The PWR_OFF bit needs to be set separately, before transitioning
+	 * to the OFF state. It enables the "sequential" power-off mode on
+	 * TPS65911, it's a NO-OP on TPS65910.
+	 */
 	if (regmap_set_bits(tps65910->regmap, TPS65910_DEVCTRL,
 			    DEVCTRL_PWR_OFF_MASK) < 0)
 		return;
 
-	regmap_clear_bits(tps65910->regmap, TPS65910_DEVCTRL,
-			  DEVCTRL_DEV_ON_MASK);
+	regmap_update_bits(tps65910->regmap, TPS65910_DEVCTRL,
+			   DEVCTRL_DEV_OFF_MASK | DEVCTRL_DEV_ON_MASK,
+			   DEVCTRL_DEV_OFF_MASK);
 }
 
 static int tps65910_i2c_probe(struct i2c_client *i2c,
-- 
2.29.2