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 ? > 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. 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 > > > >
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