| Message ID | 20221016163928.1ef0a4fe.dorota.czaplejewicz@puri.sm (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [PATCHv3,1/1,RESEND] media: imx: Round line size to 4 bytes | expand |
Hi Dorota, Thank you for the patch. On Sun, Oct 16, 2022 at 04:39:28PM +0200, Dorota Czaplejewicz wrote: > Section 13.7.6.13 "CSI Image Parameter Register" of the > i.MX 8M Quad Applications Processors Reference Manual > states that the line size should be divisible by 8 bytes. > However, the hardware also accepts sizes divisible by 4 bytes, > which are needed to fully utilize the S5K3L6XX sensors. > > This patch accepts line sizes divisible by 4 bytes. The patch itself looks fine, but I always worry when we depart from the documentation (sometimes that's a worry about documentation inaccuracies :-)). In this particular case, we need to test the change on i.MX7 too, as the alignment constraints could be platform-specific. 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. > Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm> > --- > 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;
Hi, On Mon, 17 Oct 2022 11:28:57 +0300 Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote: > Hi Dorota, > > Thank you for the patch. > > On Sun, Oct 16, 2022 at 04:39:28PM +0200, Dorota Czaplejewicz wrote: > > Section 13.7.6.13 "CSI Image Parameter Register" of the > > i.MX 8M Quad Applications Processors Reference Manual > > states that the line size should be divisible by 8 bytes. > > However, the hardware also accepts sizes divisible by 4 bytes, > > which are needed to fully utilize the S5K3L6XX sensors. > > > > This patch accepts line sizes divisible by 4 bytes. > > The patch itself looks fine, but I always worry when we depart from the > documentation (sometimes that's a worry about documentation inaccuracies > :-)). In this particular case, we need to test the change on i.MX7 too, > as the alignment constraints could be platform-specific. > I don't have access to any i.MX7 hardware, unfortunately. I can help anyone who does and wants to test this. > 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 --Dorota > > > Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm> > > --- > > 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; >
Hi all, On Mon, 17 Oct 2022 16:30:59 +0200 Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm> wrote: > Hi, > > On Mon, 17 Oct 2022 11:28:57 +0300 > Laurent Pinchart <laurent.pinchart@ideasonboard.com> 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? Cheers, Dorota > > > > > Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm> > > > --- > > > 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; > > >
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 ? You mentioned in the forum that you tried 1052x779 and that failed. How did it fail ? Have you also tried 1052x778 ? > > > > Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm> > > > > --- > > > > 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;
Hello, On Thu, 24 Nov 2022 13:30:15 +0200 Laurent Pinchart <laurent.pinchart@ideasonboard.com> 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@puri.sm> > > > > > --- > > > > > 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; >
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;
Section 13.7.6.13 "CSI Image Parameter Register" of the i.MX 8M Quad Applications Processors Reference Manual states that the line size should be divisible by 8 bytes. However, the hardware also accepts sizes divisible by 4 bytes, which are needed to fully utilize the S5K3L6XX sensors. This patch accepts line sizes divisible by 4 bytes. Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm> --- 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(-)