[PATCH] powerpc: Fix missing declaration of [en/dis]able_kernel_vsx()
Christophe Leroy
christophe.leroy at csgroup.eu
Tue Mar 9 08:52:11 UTC 2021
Le 09/03/2021 à 09:45, Geert Uytterhoeven a écrit :
> Hi Christophe,
>
> On Tue, Mar 9, 2021 at 9:39 AM Christophe Leroy
> <christophe.leroy at csgroup.eu> 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 at vger.kernel.org
>> Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
>
> 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.
>
> What about adding "depends on !POWERPC || VSX" instead, to prevent
> the issue from happening in the first place?
CONFIG_VSX is not required as pointed by the DC_FP_START() macro above and the matching DC_FP_END()
macro.
>
> Gr{oetje,eeting}s,
>
> Geert
>
Christophe
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