mbox series

[0/2] media: i2c: imx290: check for availability in probe()

Message ID 20240807-imx290-avail-v1-0-666c130c7601@skidata.com (mailing list archive)
Headers
Series media: i2c: imx290: check for availability in probe() |

Message

Benjamin Bara Aug. 7, 2024, 8:10 a.m. UTC 
  Hi!

First commit is optional and just adds the possibility to do a
cci_read() without caring about the read value. If not wanted, I can
remove it.

Second commit tries to communicate with the sensor (reading back the
STANDBY register) to find out if the sensor is available at probe time.
Currently, the first device communication is happening after the v4l2
subdev is initialized - and the communication errors are then basically
ignored.

thanks & regards
Benjamin

---
Benjamin Bara (2):
      media: v4l2-cci: Allow "empty read"
      media: i2c: imx290: Check for availability in probe()

 drivers/media/i2c/imx290.c         | 5 +++++
 drivers/media/v4l2-core/v4l2-cci.c | 5 ++++-
 include/media/v4l2-cci.h           | 2 +-
 3 files changed, 10 insertions(+), 2 deletions(-)
---
base-commit: eec5d86d5bac6b3e972eb9c1898af3c08303c52d
change-id: 20240807-imx290-avail-85795c27d988

Best regards,

Comments

Alexander Stein Aug. 7, 2024, 12:39 p.m. UTC | #1 
Am Mittwoch, 7. August 2024, 14:16:48 CEST schrieb Laurent Pinchart:
> ********************
> Achtung externe E-Mail: Öffnen Sie Anhänge und Links nur, wenn Sie wissen, dass diese aus einer sicheren Quelle stammen und sicher sind. Leiten Sie die E-Mail im Zweifelsfall zur Prüfung an den IT-Helpdesk weiter.
> Attention external email: Open attachments and links only if you know that they are from a secure source and are safe. In doubt forward the email to the IT-Helpdesk to check it.
> ********************
> 
> On Wed, Aug 07, 2024 at 02:12:04PM +0200, Alexander Stein wrote:
> > Am Mittwoch, 7. August 2024, 13:07:24 CEST schrieb Benjamin Bara:
> > > On Wed, 7 Aug 2024 at 11:50, Laurent Pinchart wrote:
> > > > On Wed, Aug 07, 2024 at 10:47:39AM +0200, Benjamin Bara wrote:
> > > > > On Wed, 7 Aug 2024 at 10:33, Alexander Stein wrote:
> > > > > > 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.
> > > >
> > > > It was a patch that I wrote as a test, and I decided not to upstream it
> > > > as it had limited value to me. The downside with reading registers at
> > > > probe time is that you have to power up the sensor. This can have
> > > > undesired side effects, such as flashing a privacy LED on at boot time
> > > > in devices that have one. There's also the increase in boot time due to
> > > > the power up sequence, which one may want to avoid.
> > > >
> > > > The imx290 driver already powers up the device unconditionally at probe
> > > > time, so reading the version register wouldn't be much of an issue I
> > > > suppose. I would be fine merging that patch.
> > > >
> > > > > 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.
> > > >
> > > > That's a good question. I don't see a mention of that register in the
> > > > IMX290 datasheet I've found online
> > > > (https://static6.arrow.com/aropdfconversion/c0c7efde6571c768020a72f59b226308b9669e45/sony_imx290lqr-c_datasheet.pdf).
> > > > Looking at the git history, the IMX290_CHIP_ID register macro was
> > > > introduced in an unrelated commit, without an explanation. I don't
> > > > recall where it comes from, but I don't think I've added it randomly. It
> > > > may have come from an out-of-tree driver.
> > > 
> > > Thanks for the info!
> > > 
> > > > I don't have an IMX290 plugged in at the moment, what's the value of the
> > > > register ?
> > > 
> > > I currently have an imx462 available, which is not "officially supported" yet,
> > > but basically an imx290 derivative. With your patch applied:
> > > 
> > > [   10.424187] imx290 7-001a: chip ID 0x07d0
> > 
> > Okay, this is from a imx327lqr:
> > 
> > [   15.265086] imx290 3-001a: chip ID 0x07d0
> > 
> > Doesn't look like an ID register to me.
> 
> Indeed, it's quite suspicious.
> 
> I wonder if we could find a more applicable register. Chip ID registers
> are usually located at the beginning or end of the register space, we
> could have a look there.

Dumping all registers (8-Bit reads) from 0x3001 till 0x3480 only has a few
non-zero registers:
> # cat /sys/kernel/debug/regmap/3-001a/range
> 3000-3480
> # cat /sys/kernel/debug/regmap/3-001a/registers  | grep -v ": 00"
> 3000: 01
> 3020: 01
> 303c: 08
> 303e: 38
> 303f: 04
> 3040: 08
> 3042: 80
> 3043: 07
> 319a: d0
> 319b: 07
> 3418: 38
> 3419: 04
> 3472: 80
> 3473: 07

Note I am on a Vision Components imx327, which might block some reads.
Laurent is also aware of that behaviour. But maybe this list gives an
indicator.

Best regards,
Alexander