linux-kernel - [PATCH v2] drivers: media: imx296: Add standby delay during probe

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Message-ID: <20241115180717.10820-1-aardelean@baylibre.com>
Date: Fri, 15 Nov 2024 20:07:17 +0200
From: Alexandru Ardelean <aardelean@...libre.com>
To: linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org
Cc: laurent.pinchart@...asonboard.com,
	manivannan.sadhasivam@...aro.org,
	sakari.ailus@...ux.intel.com,
	mchehab@...nel.org,
	kieran.bingham@...asonboard.com,
	naush@...pberrypi.com,
	Alexandru Ardelean <aardelean@...libre.com>
Subject: [PATCH v2] drivers: media: imx296: Add standby delay during probe

From: Naushir Patuck <naush@...pberrypi.com>

Add a 2-5ms delay when coming out of standby and before reading the
sensor info register durning probe, as instructed by the datasheet. This
standby delay is already present when the sensor starts streaming.

During a cold-boot, reading the IMX296_SENSOR_INFO register would often
return a value of 0x0000, if this delay is not present before.

Fixes: cb33db2b6ccfe ("media: i2c: IMX296 camera sensor driver")
Tested-by: Alexandru Ardelean <aardelean@...libre.com>
Signed-off-by: Naushir Patuck <naush@...pberrypi.com>
---

Changelog v1 -> v2:
* https://lore.kernel.org/linux-media/20241115142021.574402-1-aardelean@baylibre.com/
* Technically, this is not a true V2, but rather a new patch
  - But in V1, the attempt was to fix an issue found with the upstream
    IMX296 driver, which was pointed out by Kieran that it was already
    fixed (more elegantly) in the RPi tree.
  - The standby delay helps during a cold-boot so that the driver can read
    the IMX296_SENSOR_INFO register. If the delay isn't present the value
    read is 0xx0000.
  - Original patch can be found:
    https://github.com/raspberrypi/linux/commit/7713ce38e6a26425ace3a57b3d03ba0125c16f89
  - From the original patch of Naushir Patuck,
    - Added comment 
      -------
      During a cold-boot, reading the IMX296_SENSOR_INFO register would often 
      return a value of 0x0000, if this delay is not present before.
      -------
    - Added 'Tested-by: Alexandru Ardelean <aardelean@...libre.com>
    - Added 'Fixes: cb33db2b6ccfe ("media: i2c: IMX296 camera sensor driver")'

 drivers/media/i2c/imx296.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/i2c/imx296.c b/drivers/media/i2c/imx296.c
index f942f66fa664..395bfe4fb23d 100644
--- a/drivers/media/i2c/imx296.c
+++ b/drivers/media/i2c/imx296.c
@@ -940,6 +940,8 @@ static int imx296_identify_model(struct imx296 *sensor)
 		return ret;
 	}
 
+	usleep_range(2000, 5000);
+
 	ret = imx296_read(sensor, IMX296_SENSOR_INFO);
 	if (ret < 0) {
 		dev_err(sensor->dev, "failed to read sensor information (%d)\n",
-- 
2.46.1