Jacopo Mondi <jacopo@xxxxxxxxxx> wrote on Wed [2019-Oct-02 16:32:26 +0200]: > Hi Benoit, > > On Wed, Oct 02, 2019 at 07:14:38AM -0500, Benoit Parrot wrote: > > Hi Jacopo, > > > > Maybe, I miss spoke when I mentioned a helper I did not intent a framework > > level generic function. Just a function to help in this case :) > > Yes indeed, the discussion thread I linked here was mostly interesting > because Hugues tried to do the same for LINK_FREQ iirc, and there > where some usefult pointers. > > > > > That being said, I re-read the thread you mentioned. And as Hughes pointed > > out dynamically generating a "working" link frequency value which can be > > used by a CSI2 receiver to properly configure its PHY is not trivial. > > > > When I created this patch, I also had another to add V4L2_CID_LINK_FREQ > > support. I am testing this against the TI CAL CSI2 receiver, which already > > uses the V4L2_CID_PIXEL_RATE value for that purpose, so I also had a patch > > to add support for V4L2_CID_LINK_FREQ to that driver as well. > > > > Unfortunately, similar to Hughes' findings I was not able to make it "work" > > with all supported resolution/framerate. > > As reported by Hugues findings, the PLL calculation procedure might be > faulty, and the actuall frequencies on the bus are different from the > calculated ones. > > I wish I had more time to re-look at that, as they worked for my and > Sam's use case, but deserve some rework. > > > > > Unlike my V4L2_CID_PIXEL_RATE solution which now works in all mode with the > > same receiver. > > > > It seems to me you're reporting a fixed rate. It might make your > receiver happy, but does not report what is acutally put on the bus. > Am I missing something ? No it is not fixed, the only fixed value was the initial value (which representative of the initial/default resolution and framerate), I fixed this in v2. The reported PIXEL_RATE is re-calculated every time there is a s_fmt and/or framerate change and the V4L2_CID_PIXEL_RATE control value is updated accordingly. > > > So long story short I dropped the V4L2_CID_LINK_FREQ patch and focused on > > V4L2_CID_PIXEL_RATE instead. > > > > As Sakari pointed out, going from one to the other is trivial and > could be done on top. As you said it could be done on top. :) Benoit > > Thanks > j > > > Regard, > > Benoit > > > > Jacopo Mondi <jacopo@xxxxxxxxxx> wrote on Wed [2019-Oct-02 09:59:51 +0200]: > > > Hi Benoit, > > > +Hugues > > > > > > If you're considering an helper, this thread might be useful to you: > > > https://patchwork.kernel.org/patch/11019673/ > > > > > > Thanks > > > j > > > > > > >
