Messages in this thread | | | Subject | Re: [PATCH] powerpc: Fix missing declaration of [en/dis]able_kernel_vsx() | From | Christophe Leroy <> | Date | Wed, 10 Mar 2021 14:33:25 +0100 |
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Hi Geert,
Le 09/03/2021 à 11:55, Geert Uytterhoeven a écrit : > Hi Christophe, > > On Tue, Mar 9, 2021 at 10:58 AM Christophe Leroy > <christophe.leroy@csgroup.eu> wrote: >> Le 09/03/2021 à 10:16, Geert Uytterhoeven a écrit : >>> On Tue, Mar 9, 2021 at 9:52 AM Christophe Leroy >>> <christophe.leroy@csgroup.eu> 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@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@vger.kernel.org >>>>>> Signed-off-by: Christophe Leroy <christophe.leroy@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. >>> >>> IC. So you might as well have an empty (dummy) function instead? >>> >> >> But with an empty function, you take the risk that one day, someone calls it without checking that >> CONFIG_VSX is selected. Here if someone does that, build will fail. > > OK, convinced. >
Note that following build test performed on kisskb, with gcc 4.9 the following change is required in addition: https://patchwork.ozlabs.org/project/linuxppc-dev/patch/b231dfa040ce4cc37f702f5c3a595fdeabfe0462.1615378209.git.christophe.leroy@csgroup.eu/
Christophe
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