media: imx-pxp: Rewrite coeff expression

[PATCH] media: imx-pxp: Rewrite coeff expression

Posted by Ricardo Ribalda 1 year, 5 months ago

GCC5 cannot figure out that the expressions are constant, and that
triggers a build failure. Rewrite the expressions.

The following gcc5 error is workaround:

 #define BM_PXP_CSC1_COEF0_YCBCR_MODE 0x80000000
                                      ^
    BM_PXP_CSC1_COEF0_YCBCR_MODE |
    ^
 #define BM_PXP_CSC1_COEF0_YCBCR_MODE 0x80000000
                                      ^

drivers/media/platform/nxp/imx-pxp.c: In function 'pxp_setup_csc':
drivers/media/platform/nxp/imx-pxp.h:582:38: error: initializer element is not constant
drivers/media/platform/nxp/imx-pxp.c:374:4: note: in expansion of macro 'BM_PXP_CSC1_COEF0_YCBCR_MODE'
drivers/media/platform/nxp/imx-pxp.h:582:38: note: (near initialization for 'csc1_coef_bt601_lim[0]')
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
While implementing media-ci, we have found this build error with gcc5.
---
 drivers/media/platform/nxp/imx-pxp.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/nxp/imx-pxp.h b/drivers/media/platform/nxp/imx-pxp.h
index 44f95c749d2e..ae4c6021c156 100644
--- a/drivers/media/platform/nxp/imx-pxp.h
+++ b/drivers/media/platform/nxp/imx-pxp.h
@@ -594,12 +594,17 @@
 	(((v) << 18) & BM_PXP_CSC1_COEF0_C0)
 #define BP_PXP_CSC1_COEF0_UV_OFFSET      9
 #define BM_PXP_CSC1_COEF0_UV_OFFSET 0x0003FE00
+
+/*
+ * We use v * (1 << 9) instead of v << 9, to workaround a gcc5 bug.
+ * The compiler cannot understand that the expression is constant.
+*/
 #define BF_PXP_CSC1_COEF0_UV_OFFSET(v)  \
-	(((v) << 9) & BM_PXP_CSC1_COEF0_UV_OFFSET)
+	(((v) * (1 << 9)) & BM_PXP_CSC1_COEF0_UV_OFFSET)
 #define BP_PXP_CSC1_COEF0_Y_OFFSET      0
 #define BM_PXP_CSC1_COEF0_Y_OFFSET 0x000001FF
 #define BF_PXP_CSC1_COEF0_Y_OFFSET(v)  \
-	(((v) << 0) & BM_PXP_CSC1_COEF0_Y_OFFSET)
+	((v) & BM_PXP_CSC1_COEF0_Y_OFFSET)
 
 #define HW_PXP_CSC1_COEF1	(0x000001b0)
 

---
base-commit: 6aa082910445aec6b1dc652a69c5178a555d8ca5
change-id: 20240628-gcc5-71a968c78e98

Best regards,
-- 
Ricardo Ribalda <ribalda@chromium.org>

Re: [PATCH] media: imx-pxp: Rewrite coeff expression

Posted by Philipp Zabel 1 year, 5 months ago

On Fr, 2024-06-28 at 15:11 +0000, Ricardo Ribalda wrote:
> GCC5 cannot figure out that the expressions are constant, and that
> triggers a build failure. Rewrite the expressions.
> 
> The following gcc5 error is workaround:
> 
>  #define BM_PXP_CSC1_COEF0_YCBCR_MODE 0x80000000
>                                       ^
>     BM_PXP_CSC1_COEF0_YCBCR_MODE |
>     ^
>  #define BM_PXP_CSC1_COEF0_YCBCR_MODE 0x80000000
>                                       ^
> 
> drivers/media/platform/nxp/imx-pxp.c: In function 'pxp_setup_csc':
> drivers/media/platform/nxp/imx-pxp.h:582:38: error: initializer element is not constant
> drivers/media/platform/nxp/imx-pxp.c:374:4: note: in expansion of macro 'BM_PXP_CSC1_COEF0_YCBCR_MODE'
> drivers/media/platform/nxp/imx-pxp.h:582:38: note: (near initialization for 'csc1_coef_bt601_lim[0]')
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>

Can you elaborate on how this is triggered?

At least I couldn't reproduce this by just copy & pasting the
csc1_coef_bt601_lim initializer and the required macros into gcc 5.4 on
godbolt.

Can this be fixed by using GENMASK / FIELD_PREP instead?

regards
Philipp

Re: [PATCH] media: imx-pxp: Rewrite coeff expression

Posted by Ricardo Ribalda 1 year, 5 months ago

Hi Philipp


On Mon, 1 Jul 2024 at 11:30, Philipp Zabel <p.zabel@pengutronix.de> wrote:
>
> On Fr, 2024-06-28 at 15:11 +0000, Ricardo Ribalda wrote:
> > GCC5 cannot figure out that the expressions are constant, and that
> > triggers a build failure. Rewrite the expressions.
> >
> > The following gcc5 error is workaround:
> >
> >  #define BM_PXP_CSC1_COEF0_YCBCR_MODE 0x80000000
> >                                       ^
> >     BM_PXP_CSC1_COEF0_YCBCR_MODE |
> >     ^
> >  #define BM_PXP_CSC1_COEF0_YCBCR_MODE 0x80000000
> >                                       ^
> >
> > drivers/media/platform/nxp/imx-pxp.c: In function 'pxp_setup_csc':
> > drivers/media/platform/nxp/imx-pxp.h:582:38: error: initializer element is not constant
> > drivers/media/platform/nxp/imx-pxp.c:374:4: note: in expansion of macro 'BM_PXP_CSC1_COEF0_YCBCR_MODE'
> > drivers/media/platform/nxp/imx-pxp.h:582:38: note: (near initialization for 'csc1_coef_bt601_lim[0]')
> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
>
> Can you elaborate on how this is triggered?

Building the driver with
https://cdn.kernel.org/pub/tools/crosstool/files/bin/x86_64/5.5.0/

It might be easier to repro with:

ribalda@denia:~/work/linux$ podman run --pids-limit=-1 --rm -it -v
.:/workdir  registry.freedesktop.org/linux-media/media-ci/build-ancient
# cd /workdir
# CROSS_COMPILE=x86_64-linux- make allyesconfig
# scripts/config -d MITIGATION_RETPOLINE
# CROSS_COMPILE=x86_64-linux- make olddefconfig
# CROSS_COMPILE=x86_64-linux- make drivers/media/platform/nxp/


>
> At least I couldn't reproduce this by just copy & pasting the
> csc1_coef_bt601_lim initializer and the required macros into gcc 5.4 on
> godbolt.
>
> Can this be fixed by using GENMASK / FIELD_PREP instead?

I was looking to make the change as simple as possible :)

>
> regards
> Philipp



-- 
Ricardo Ribalda