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

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Message-ID: <173192451835.576258.8765067630505878740@ping.linuxembedded.co.uk>
Date: Mon, 18 Nov 2024 10:08:38 +0000
From: Kieran Bingham <kieran.bingham@...asonboard.com>
To: Alexandru Ardelean <aardelean@...libre.com>, 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, naush@...pberrypi.com, Alexandru Ardelean <aardelean@...libre.com>
Subject: Re: [PATCH v2] drivers: media: imx296: Add standby delay during probe

Quoting Alexandru Ardelean (2024-11-15 18:07:17)
> 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.

Thanks,


Reviewed-by: Kieran Bingham <kieran.bingham@...asonboard.com>

>   - 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
>