Re: [PATCH 1/7] media: i2c: ov7251: Fix link frequency index

[D. Manresa <dmanresa@gmail.com>]

Hi Dave,

On Tue, 27 Oct 2026 at 16:50, Dave Stevenson wrote:
> @D. Manresa it'd be worth trying using a prediv instead of (post)div:
>     .pre_div = 0x04,
>     .mult = 0x85,
>     .div = 0x01,

Our mails crossed, and that is exactly the change I had just finished
measuring, from a test patch Antoine sent me. It fixes the link on this
receiver: thirteen 150-frame runs at 30 fps, every one 150 of 150 in
5.2 s with zero dropped buffers and zero CSI-2 error lines, against
seven bad runs out of ten with the index fix alone, three of them hard
stalls. i2c readback mid-stream confirms 0x30b4 = 0x04 and 0x30b1 =
0x01 with link_frequency still 319200000, so the link rate is unchanged
and only the VCO moved. Full numbers are in my other mail on this
thread, which went out a few minutes after yours arrived and does not
mention you only because I had not yet seen it.

So the 19.2 MHz / 319.2 MHz mode you could not test behaves exactly as
your 24 MHz oscilloscope measurements predict.

Dan's instinct in the parallel branch was right too: it was the
driver's PLL settings and not the value ipu-bridge advertises.

One data point on VBLANK, since you raised it. With 2/7 of this series
the 90 fps mode runs at vblank 92, and in its clean runs it logged no
CSI-2 errors and no corruption I could see here. I did not go below 40,
so I can neither confirm nor contradict that part.

D. Manresa

(Written with AI assistance, directed and reviewed by me.)