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

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Message-ID: <20241116164705.GC12409@pendragon.ideasonboard.com>
Date: Sat, 16 Nov 2024 18:47:05 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Alexandru Ardelean <aardelean@...libre.com>
Cc: linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	manivannan.sadhasivam@...aro.org, sakari.ailus@...ux.intel.com,
	mchehab@...nel.org, kieran.bingham@...asonboard.com,
	naush@...pberrypi.com
Subject: Re: [PATCH v2] drivers: media: imx296: Add standby delay during probe

Hi Alexandru, Naush,

Thank you for the patch.

On Fri, Nov 15, 2024 at 08:07:17PM +0200, Alexandru Ardelean wrote:
> 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>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.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",

-- 
Regards,

Laurent Pinchart