Hello, On Thu, 24 Nov 2022 13:30:15 +0200 Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > Hi Dorota, > > On Tue, Nov 01, 2022 at 01:38:34PM +0100, Dorota Czaplejewicz wrote: > > On Mon, 17 Oct 2022 16:30:59 +0200 Dorota Czaplejewicz wrote: > > > On Mon, 17 Oct 2022 11:28:57 +0300 Laurent Pinchart wrote: > > > > [snip] > > > > > > I would also very much appreciate feedback from NXP on this. There's a > > > > risk of ill side-effects that I would prefer ruling out very clearly. > > > > > > I posted a question on the NXP forum: https://community.nxp.com/t5/i-MX-Processors/i-MX8MQ-CSI-line-size-constraint-documentation-mistake/m-p/1538629#M196448 > > > > > > > This question received a reply from NXP today: https://community.nxp.com/t5/i-MX-Processors/i-MX8MQ-CSI-line-size-constraint-documentation-mistake/m-p/1546872/highlight/true#M197067 > > > > Quoting NXP's answer: > > > > > Do I understand correctly, that streams divisible by 4×4 will work on other i.MX8 hardware too? - Yes > > > Will those kind of resolutions work on i.MX7 series CSI hardware? - Yes > > > > which implies no bad side effects the way I read it. Is this > > sufficient for the kernel? > > Ideally I'd like to test that on i.MX7 but I don't think I'll have time > to do so in the near future. I don't want to block the patch on this, so > I'm fine merging it, but I'd like a comment in the code that explains > why it's safe to depart from the documentation. > > Also, the discussion on the NXP forum said that a width that is a > multiple of 4 bytes but not a multiple of 8 bytes works only if the > height is also a multiple of 4. I don't see that constraint being > enforced in the code, am I missing something ? Thanks for pointing it out, I'll have to double-check it. > > You mentioned in the forum that you tried 1052x779 and that failed. How > did it fail ? Have you also tried 1052x778 ? I tried with many resolutions when I was checking out the sensor, and came to the conclusion that the line count must be even. Otherwise the last 4 bytes of the buffer would end up corrupted. My guess is that the copy engine can indeed only do bursts of 8 bytes, but that the whole buffer is copied at once rather than line-by-line. > > > > > > Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@xxxxxxx> > > > > > --- > > > > > Hello, > > > > > > > > > > the Librem 5 is using an out-of-tree driver for s5k3l6xx, and > > > > > rounding to 4 is optimal to operate it. > > > > > > > > > > This revision improves the commit message. > > > > > > > > > > Cheers, > > > > > Dorota Czaplejewicz > > > > > > > > > > drivers/staging/media/imx/imx7-media-csi.c | 4 ++-- > > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/drivers/staging/media/imx/imx7-media-csi.c b/drivers/staging/media/imx/imx7-media-csi.c > > > > > index a0553c24cce4..af821b410c3f 100644 > > > > > --- a/drivers/staging/media/imx/imx7-media-csi.c > > > > > +++ b/drivers/staging/media/imx/imx7-media-csi.c > > > > > @@ -999,10 +999,10 @@ static int imx7_csi_mbus_fmt_to_pix_fmt(struct v4l2_pix_format *pix, > > > > > } > > > > > > > > > > /* Round up width for minimum burst size */ > > > > > - width = round_up(mbus->width, 8); > > > > > + width = round_up(mbus->width, 4); > > > > > > > > > > /* Round up stride for IDMAC line start address alignment */ > > > > > - stride = round_up((width * cc->bpp) >> 3, 8); > > > > > + stride = round_up((width * cc->bpp) >> 3, 4); > > > > > > > > > > pix->width = width; > > > > > pix->height = mbus->height; >
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