Hi Christophe,
On Tue, Mar 9, 2021 at 9:52 AM Christophe Leroy
<christophe.leroy@xxxxxxxxxx> wrote:
> Le 09/03/2021 à 09:45, Geert Uytterhoeven a écrit :
> > On Tue, Mar 9, 2021 at 9:39 AM Christophe Leroy
> > <christophe.leroy@xxxxxxxxxx> wrote:
> >> Add stub instances of enable_kernel_vsx() and disable_kernel_vsx()
> >> when CONFIG_VSX is not set, to avoid following build failure.
> >>
> >> CC [M] drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.o
> >> In file included from ./drivers/gpu/drm/amd/amdgpu/../display/dc/dm_services_types.h:29,
> >> from ./drivers/gpu/drm/amd/amdgpu/../display/dc/dm_services.h:37,
> >> from drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.c:27:
> >> drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.c: In function 'dcn_bw_apply_registry_override':
> >> ./drivers/gpu/drm/amd/amdgpu/../display/dc/os_types.h:64:3: error: implicit declaration of function 'enable_kernel_vsx'; did you mean 'enable_kernel_fp'? [-Werror=implicit-function-declaration]
> >> 64 | enable_kernel_vsx(); \
> >> | ^~~~~~~~~~~~~~~~~
> >> drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.c:640:2: note: in expansion of macro 'DC_FP_START'
> >> 640 | DC_FP_START();
> >> | ^~~~~~~~~~~
> >> ./drivers/gpu/drm/amd/amdgpu/../display/dc/os_types.h:75:3: error: implicit declaration of function 'disable_kernel_vsx'; did you mean 'disable_kernel_fp'? [-Werror=implicit-function-declaration]
> >> 75 | disable_kernel_vsx(); \
> >> | ^~~~~~~~~~~~~~~~~~
> >> drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.c:676:2: note: in expansion of macro 'DC_FP_END'
> >> 676 | DC_FP_END();
> >> | ^~~~~~~~~
> >> cc1: some warnings being treated as errors
> >> make[5]: *** [drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.o] Error 1
> >>
> >> Fixes: 16a9dea110a6 ("amdgpu: Enable initial DCN support on POWER")
> >> Cc: stable@xxxxxxxxxxxxxxx
> >> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> >
> > Thanks for your patch!
> >
> >> --- a/arch/powerpc/include/asm/switch_to.h
> >> +++ b/arch/powerpc/include/asm/switch_to.h
> >> @@ -71,6 +71,16 @@ static inline void disable_kernel_vsx(void)
> >> {
> >> msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);
> >> }
> >> +#else
> >> +static inline void enable_kernel_vsx(void)
> >> +{
> >> + BUILD_BUG();
> >> +}
> >> +
> >> +static inline void disable_kernel_vsx(void)
> >> +{
> >> + BUILD_BUG();
> >> +}
> >> #endif
> >
> > I'm wondering how this is any better than the current situation: using
> > BUILD_BUG() will still cause a build failure?
>
> No it won't cause a failure. In drivers/gpu/drm/amd/display/dc/os_types.h you have:
>
> #define DC_FP_START() { \
> if (cpu_has_feature(CPU_FTR_VSX_COMP)) { \
> preempt_disable(); \
> enable_kernel_vsx(); \
> } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) { \
> preempt_disable(); \
> enable_kernel_altivec(); \
> } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) { \
> preempt_disable(); \
> enable_kernel_fp(); \
> } \
>
> When CONFIG_VSX is not selected, cpu_has_feature(CPU_FTR_VSX_COMP) constant folds to 'false' so the
> call to enable_kernel_vsx() is discarded and the build succeeds.
IC. So you might as well have an empty (dummy) function instead?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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