Re: [PATCH 2/4] media: i2c: Add ST VD55G0 global shutter sensor driver

[Sergey Lebedev <lsa.uz@pm.me>]

Hi George,

Thank you for trying it on the Snapdragon model.

On 19/10/2026 19:24, George Neacsu wrote:
> As posted, patch 2/4 fails probe at the integer-multiple check because
> 840 MHz is not an integer multiple of 19.2 MHz.

That refusal is deliberate. The MIPI rate is an integer multiple of the
input clock, and the sensor rounds a request down (UM2829 13.6): asked
for 840 Mbps from 19.2 MHz, it runs at 825.6 while the receiver is set
up for 840. camera-sensor.rst asks a sensor driver to use only the link
frequencies the firmware gives, so the driver refuses one it cannot
produce. From 19.2 MHz, 403.2 MHz (806.4 Mbps, 42 times the clock) and
384 MHz (768 Mbps, 40 times) are exact, so the change is one value in
your board's DT, in the sensor endpoint:

	link-frequencies = /bits/ 64 <403200000>;

On the Intel model I ran it at 403.2 MHz with a 19.2 MHz clock, and every
mode ran at 60.22 fps, as the controls give.

> For a test only, I removed that rejection and left the rest of the driver
> unchanged. The sensor then probes, the CAMSS media graph completes, and
> capture delivers one complete 644x604 Y10 frame. A continuous five-frame
> capture then times out waiting for frame 2.

With the check removed, the sensor runs at 825.6 Mbps against a receiver
set up for 840, and the driver reports a pixel rate of 140 MHz where it
is 137.6. I do not know whether CAMSS minds, but a run at 403.2 MHz with
the driver as posted would take that out of the question. If it still
stops after one frame, I would be glad to compare what the two drivers
write at stream start.

Sergey