[PATCH v3 08/15] media: mt9m114: Put sensor in reset on power down

[Hans de Goede <hansg@kernel.org>]

Put the sensor back in reset on power down. Putting the sensor in reset
reduces power-consumption by putting all the data / ctrl pins in High-Z
mode. This helps save power on designs where the regulators may need to
stay on while the sensor is powered down.

This also ensures that the sensor is properly reset on power up,
since now the sensor will see a reset high to low transition after
the regulators have been turned on.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans de Goede <hansg@kernel.org>
---
Changes in v3:
- Improve commit message

Changes in v2
- After setting reset high wait 20 clk cycles before disabling
  the clk and regulators
---
 drivers/media/i2c/mt9m114.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/media/i2c/mt9m114.c b/drivers/media/i2c/mt9m114.c
index c10100d8fd4a..d4aad77b095b 100644
--- a/drivers/media/i2c/mt9m114.c
+++ b/drivers/media/i2c/mt9m114.c
@@ -2207,6 +2207,13 @@ static int mt9m114_power_on(struct mt9m114 *sensor)
 
 static void mt9m114_power_off(struct mt9m114 *sensor)
 {
+	unsigned int duration;
+
+	gpiod_set_value(sensor->reset, 1);
+	/* Power off takes 10 clock cycles. Double it to be safe. */
+	duration = DIV_ROUND_UP(2 * 10 * 1000000, sensor->clk_freq);
+	fsleep(duration);
+
 	clk_disable_unprepare(sensor->clk);
 	regulator_bulk_disable(ARRAY_SIZE(sensor->supplies), sensor->supplies);
 }
-- 
2.49.0