Re: [PATCH v2 1/9] media: i2c: ov7251: Use in-range PLL1 dividers for the 319.2 MHz link

[Antoine Pichot <antoine.pichot@gmail.com>]

Hi Dave,

On Thu, Oct 29, 2026 at 07:06:31PM +0000, Dave Stevenson wrote:
> I have a 24MHz module and had tested with it, which you'd acknowledged
> in the previous sentence.

You are right, sorry. v3 replaces that sentence: the 24 MHz tables are
left to a separate change, with your measurement cited.

> I've pushed where I am to
> https://github.com/6by9/linux/tree/rpi-7.3.y-ov7251. Patch "media:
> ov7251: Add support for a 400MHz link freq" fixes up all the 24MHz PLL
> settings. I've also done the conversion to use the V4L2 CCI library.

Thanks. For v3 I am taking your "Move the common registers into the
global init table" as patch 7, under your authorship, in place of my
strobe-register patch: the strobe registers now sit in
ov7251_global_init_setting, which answers your question on 5/7 of v1.

The move has two side effects on the bus, both in the commit message:

- The common registers are written at power-on instead of at every
  stream start, so a restart within the runtime PM autosuspend delay
  skips them. The datasheet allows it (table 2-8: software standby
  keeps the register values).
- Register 0x3820 holds 0x40 while the sensor streams, where it held
  0x00 before. The flip control writes back the value probe cached,
  and probe now caches it after the init table has written 0x40, not
  right after the reset when it read 0x00. I poked the old value in
  during a lit stream: brightness, picture, orientation and frame
  rate did not change.

Tested on the Book 2 against v2: the clock, timing, PLL, flip and
strobe registers read back while streaming at 30, 60 and 90 fps are
identical apart from 0x3820. On a sensor kept powered, a restart and
mode switches from 30 to 90, to 60 and back to 30 fps give a correct
first frame every time, at 90.45, 60.15 and 30.0 fps.

The rest of your branch (400 MHz, CCI, HBLANK and MIN_HTS, the
optional enable GPIO, the gain rename, the VBLANK minimum) I leave to
you as you offered, to keep v3 to the fixes and the IR camera. I can
test them on the Book 2 (19.2 MHz, 319.2 MHz link) when you post them.
Two things for that:

- A data point for the VBLANK minimum. A sweep on the Book 2 in the
  30 fps mode (exposure 400, gain 16, 20 frames per value) gives
  normal frames down to 41, white frames from 40 to 26 and frames
  rolled sideways from 25 to 16, both without CSI-2 errors, CRC
  errors from 13 and a stalled receiver at 10. The same boundary as
  on your Pi.
- At the tip of the branch (fde519da0503, "media: ov7251: Reduce
  OV7251_TIMING_MIN_HTS"), unless I misread it, ov7251_set_vflip()
  writes OV7251_TIMING_FORMAT2 (0x3821) rather than 0x3820, probe
  stores the 0x3821 read in timing_format1 rather than
  timing_format2, and the return value of devm_cci_regmap_init_i2c()
  is not checked. In case it helps before you post.

Thanks,
Antoine