linux-kernel - Re: [PATCH 2/2] media: i2c: imx290: Check for availability in probe()

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Message-ID: <6072611.lOV4Wx5bFT@steina-w>
Date: Wed, 07 Aug 2024 10:33:51 +0200
From: Alexander Stein <alexander.stein@...tq-group.com>
To: Mauro Carvalho Chehab <mchehab@...nel.org>, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Sakari Ailus <sakari.ailus@...ux.intel.com>, Benjamin Bara <bbara93@...il.com>
Cc: Hans de Goede <hdegoede@...hat.com>, Laurent Pinchart <laurent.pinchart@...asonboard.com>, linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, Benjamin Bara <benjamin.bara@...data.com>
Subject: Re: [PATCH 2/2] media: i2c: imx290: Check for availability in probe()

Hi Benjamin,

Am Mittwoch, 7. August 2024, 10:10:28 CEST schrieb Benjamin Bara:
> Currently, the V4L2 subdevice is also created when the device is not
> available/connected. In this case, dmesg shows the following:
> 
> [   10.419510] imx290 7-001a: Error writing reg 0x301c: -6
> [   10.428981] imx290 7-001a: Error writing reg 0x3020: -6
> [   10.442712] imx290 7-001a: Error writing reg 0x3018: -6
> [   10.454018] imx290 7-001a: Error writing reg 0x3020: -6
> 
> which seems to come from imx290_ctrl_update() after the subdev init is
> finished. However, as the errors are ignored, the subdev is initialized
> but simply does not work. From userspace perspective, there is no
> visible difference between a working and not-working subdevice (except
> when trying it out or watching for the error message).
> 
> This commit adds a simple availability check before starting with the
> subdev initialization to error out instead.

There is already a patch reading the ID register at [1]. This also reads the
ID register. But I don't have any documentation regarding that register,
neither address nor values definitions. If there is known information about
that I would prefer reading the ID and compare it to expected values.

Best regards,
Alexander

[1] https://gitlab.com/ideasonboard/nxp/linux/-/commit/85ce725f1de7c16133bfb92b2ab0d3d84efcdb47

> Signed-off-by: Benjamin Bara <benjamin.bara@...data.com>
> ---
>  drivers/media/i2c/imx290.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/media/i2c/imx290.c b/drivers/media/i2c/imx290.c
> index 4150e6e4b9a6..a86076e42a36 100644
> --- a/drivers/media/i2c/imx290.c
> +++ b/drivers/media/i2c/imx290.c
> @@ -1580,6 +1580,11 @@ static int imx290_probe(struct i2c_client *client)
>  	pm_runtime_set_autosuspend_delay(dev, 1000);
>  	pm_runtime_use_autosuspend(dev);
>  
> +	/* Make sure the sensor is available before V4L2 subdev init. */
> +	ret = cci_read(imx290->regmap, IMX290_STANDBY, NULL, NULL);
> +	if (ret)
> +		goto err_pm;
> +
>  	/* Initialize the V4L2 subdev. */
>  	ret = imx290_subdev_init(imx290);
>  	if (ret)
> 
> 


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