Re: [PATCH v4 3/6] media: i2c: ov5693: Gate the MIPI clock lane for non-continuous clock

[Fernando Rimoli]

Hi Jakob,

Thank you, and thanks for re-testing rather than letting the old tag stand.

I will carry the tag on patches 3 to 6 as you scoped it, and not on 1 and
2, since your machine enumerates INT33BE and neither of those is exercised
there.

The register read-back is the most valuable part. Nobody
had shown the mechanism working end to end before: 0x4800 reading 0x00
unpatched and 0x20 patched, with the chip ID as a bus control, demonstrates
that the bridge really did supply clock-noncontinuous, that the driver
acted on it, and that the read-modify-write set bit 5 and disturbed nothing
else.

Your unpatched result also corrects something I should fix. You saw 3 of 20
runs deliver frames without the series; on my Pro 9 the unpatched case is a
hard zero every time. So the failure is intermittent on Tiger Lake rather
than absolute, and patch 3's commit message currently reads as though it
always fails.

That is too strong given your data. In v5 I will say the receiver usually
fails to lock, note that it is intermittent on some units, and cite your 3
of 20 alongside my 0 of N.

Two smaller things from your mail worth recording. Your read of 0x00 on the
unpatched Tiger Lake machine confirms on a second IPU generation that the
whole-register write and the read-modify-write resolve to the same value,
so that argument in the cover letter is no longer only about my Pro 9. And
you have answered the caveat Zann580 attached to the 0x20 row on GitHub,
which was that the minimal value should be confirmed from a built module
rather than from a userspace poke before the patch was narrowed on its
strength. It now has been.

Thanks again,
Fernando