Re: [PATCH] drm/meson: overlay: fix build failure

[Neil Armstrong]

On 07/07/2020 15:50, Neil Armstrong wrote:
> The recent GCC compiler is very picky with the VD_H_START() and
> AFBC_DEC_PIXEL_BGN_H() macros, triggering a runtime assert error as:
> 
> In function 'meson_overlay_setup_scaler_params',
>     inlined from 'meson_overlay_atomic_update' at
> drivers/gpu/drm/meson/meson_overlay.c:542:2:
> ./include/linux/compiler.h:392:38: error: call to
> '__compiletime_assert_341' declared with attribute error: FIELD_PREP:
> value too large for the field
> 
> drivers/gpu/drm/meson/meson_overlay.c:413:4: note: in expansion of macro
> 'AFBC_DEC_PIXEL_BGN_H'
>   413 |    AFBC_DEC_PIXEL_BGN_H(hd_start_lines - afbc_left) |
>       |    ^~~~~~~~~~~~~~~~~~~~
> ./include/linux/compiler.h:392:38: error: call to
> '__compiletime_assert_401' declared with attribute error: FIELD_PREP:
> value too large for the field
> 
> It's not expected to overflow these fields, but the compiler did
> find a case where it overflows.
> We can safely ignore this, so mask the value with the field width.
> 
> Fixes: e860785d57306 ("drm/meson: overlay: setup overlay for Amlogic FBC")
> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
> Got Daniel's Ack from irc
> 
>  drivers/gpu/drm/meson/meson_overlay.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/meson/meson_overlay.c b/drivers/gpu/drm/meson/meson_overlay.c
> index 1f7b2055e012..646e605f30f3 100644
> --- a/drivers/gpu/drm/meson/meson_overlay.c
> +++ b/drivers/gpu/drm/meson/meson_overlay.c
> @@ -58,7 +58,8 @@
>  
>  /* VPP_POSTBLEND_VD1_H_START_END */
>  #define VD_H_END(value)			FIELD_PREP(GENMASK(11, 0), value)
> -#define VD_H_START(value)		FIELD_PREP(GENMASK(27, 16), value)
> +#define VD_H_START(value)		FIELD_PREP(GENMASK(27, 16), \
> +						   (value & GENMASK(13, 0)))
>  
>  /* VPP_POSTBLEND_VD1_V_START_END */
>  #define VD_V_END(value)			FIELD_PREP(GENMASK(11, 0), value)
> @@ -144,7 +145,8 @@
>  #define AFBC_MIF_BLK_END_V(value)	FIELD_PREP(GENMASK(11, 0), value)
>  
>  /* AFBC_PIXEL_HOR_SCOPE */
> -#define AFBC_DEC_PIXEL_BGN_H(value)	FIELD_PREP(GENMASK(28, 16), value)
> +#define AFBC_DEC_PIXEL_BGN_H(value)	FIELD_PREP(GENMASK(28, 16), \
> +						   (value & GENMASK(12, 0)))
>  #define AFBC_DEC_PIXEL_END_H(value)	FIELD_PREP(GENMASK(12, 0), value)
>  
>  /* AFBC_PIXEL_VER_SCOPE */
> 

Applied to drm-misc-next