linux-kernel - [PATCH v4 2/3] media: i2c: imx290: Avoid communication during probe()

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Message-Id: <20240903-imx290-avail-v4-2-e4a6c0837f0b@skidata.com>
Date: Tue, 03 Sep 2024 16:54:33 +0200
From: Benjamin Bara <bbara93@...il.com>
To: Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
 Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc: Hans de Goede <hdegoede@...hat.com>, 
 Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Alexander Stein <alexander.stein@...tq-group.com>, 
 Dave Stevenson <dave.stevenson@...pberrypi.com>, 
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Benjamin Bara <benjamin.bara@...data.com>
Subject: [PATCH v4 2/3] media: i2c: imx290: Avoid communication during
 probe()

From: Benjamin Bara <benjamin.bara@...data.com>

As we don't know the mode during probe(), it doesn't make sense to
update the sensors' registers with assumptions. As imx290_set_ctrl(),
which is responsible for the happening communication, already ensures that
there is no communication with a suspended sensor, put the sensor to
suspend before calling it.

To clarify the dependency of the PM runtime to the link of the subdev
and the imx290 instance, put the block together.

Suggested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Benjamin Bara <benjamin.bara@...data.com>
---
Changes since v3:
- just rely on the already available runtime PM check in
  imx290_set_ctrl(), as suggested by Laurent.
- add S-b for Laurent (thanks for the idea and the feedback).
- reword commit message.
---
 drivers/media/i2c/imx290.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/media/i2c/imx290.c b/drivers/media/i2c/imx290.c
index 5e4aa7237152..47cfb6a9e9b5 100644
--- a/drivers/media/i2c/imx290.c
+++ b/drivers/media/i2c/imx290.c
@@ -1249,11 +1249,21 @@ static int imx290_subdev_init(struct imx290 *imx290)
 
 	imx290->current_mode = &imx290_modes_ptr(imx290)[0];
 
+	/*
+	 * After linking the subdev with the imx290 instance, we are allowed to
+	 * use the pm_runtime functions. Decrease the PM usage count. The device
+	 * will get suspended after the autosuspend delay, turning the power
+	 * off. However, the communication happening in imx290_ctrl_update()
+	 * will already be prevented even before the delay.
+	 */
 	v4l2_i2c_subdev_init(&imx290->sd, client, &imx290_subdev_ops);
+	imx290->sd.dev = imx290->dev;
+	pm_runtime_mark_last_busy(imx290->dev);
+	pm_runtime_put_autosuspend(imx290->dev);
+
 	imx290->sd.internal_ops = &imx290_internal_ops;
 	imx290->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE |
 			    V4L2_SUBDEV_FL_HAS_EVENTS;
-	imx290->sd.dev = imx290->dev;
 	imx290->sd.entity.ops = &imx290_subdev_entity_ops;
 	imx290->sd.entity.function = MEDIA_ENT_F_CAM_SENSOR;
 
@@ -1598,13 +1608,6 @@ static int imx290_probe(struct i2c_client *client)
 		goto err_subdev;
 	}
 
-	/*
-	 * Decrease the PM usage count. The device will get suspended after the
-	 * autosuspend delay, turning the power off.
-	 */
-	pm_runtime_mark_last_busy(dev);
-	pm_runtime_put_autosuspend(dev);
-
 	return 0;
 
 err_subdev:

-- 
2.46.0