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

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Message-ID: <CAJpcXm6Bv37GUsttdGDDgX1Do+KC_xVSwHV7M5_aEuvhuv6u3A@mail.gmail.com>
Date: Wed, 7 Aug 2024 10:47:39 +0200
From: Benjamin Bara <bbara93@...il.com>
To: Alexander Stein <alexander.stein@...tq-group.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, 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 Alexander,

On Wed, 7 Aug 2024 at 10:33, Alexander Stein
<alexander.stein@...tq-group.com> wrote:
> 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.

Thanks for the link - it seems like Laurent has dropped the patch for
the more recent kernel versions on their GitLab.

This was also my initial intention, but similar to you, I don't have a
docu describing this register, so I am not sure where the info is coming
from and if it really contains the identification/type info. Probably
Laurent has more infos on that.

Best regards
Benjamin

> 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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