linux-kernel - [PATCH v4 08/15] media: mt9m114: Put sensor in reset on power down

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Message-Id: <20251224-mt9m114-atomisp-v4-8-60b25da7a1bc@oss.qualcomm.com>
Date: Wed, 24 Dec 2025 13:31:17 +0100
From: Hans de Goede <johannes.goede@....qualcomm.com>
To: Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Hans de Goede <johannes.goede@....qualcomm.com>
Subject: [PATCH v4 08/15] media: mt9m114: Put sensor in reset on power down

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@...asonboard.com>
Signed-off-by: Hans de Goede <johannes.goede@....qualcomm.com>
---
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 60afc32acee4df1e7d4f820838b72f6aa3506f8d..39f9d20221fee4f1d12c24a031d9f33c953b9a9c 100644
--- a/drivers/media/i2c/mt9m114.c
+++ b/drivers/media/i2c/mt9m114.c
@@ -2228,6 +2228,13 @@ 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, clk_get_rate(sensor->clk));
+	fsleep(duration);
+
 	clk_disable_unprepare(sensor->clk);
 	regulator_bulk_disable(ARRAY_SIZE(sensor->supplies), sensor->supplies);
 }

-- 
2.52.0