On 2023-12-11 6:23 AM, Michael Ellerman wrote:
> Hi Samuel,
>
> Thanks for trying to clean all this up.
>
> One problem below.
>
> Samuel Holland <samuel.holland@xxxxxxxxxx> writes:
>> Now that all previously-supported architectures select
>> ARCH_HAS_KERNEL_FPU_SUPPORT, this code can depend on that symbol instead
>> of the existing list of architectures. It can also take advantage of the
>> common kernel-mode FPU API and method of adjusting CFLAGS.
>>
>> Signed-off-by: Samuel Holland <samuel.holland@xxxxxxxxxx>
> ...
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
>> index 4ae4720535a5..b64f917174ca 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
>> @@ -87,20 +78,9 @@ void dc_fpu_begin(const char *function_name, const int line)
>> WARN_ON_ONCE(!in_task());
>> preempt_disable();
>> depth = __this_cpu_inc_return(fpu_recursion_depth);
>> -
>> if (depth == 1) {
>> -#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
>> + BUG_ON(!kernel_fpu_available());
>> kernel_fpu_begin();
>> -#elif defined(CONFIG_PPC64)
>> - if (cpu_has_feature(CPU_FTR_VSX_COMP))
>> - enable_kernel_vsx();
>> - else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP))
>> - enable_kernel_altivec();
>
> Note altivec.
>
>> - else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
>> - enable_kernel_fp();
>> -#elif defined(CONFIG_ARM64)
>> - kernel_neon_begin();
>> -#endif
>> }
>>
>> TRACE_DCN_FPU(true, function_name, line, depth);
>> diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
>> index ea7d60f9a9b4..5aad0f572ba3 100644
>> --- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
>> +++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
>> @@ -25,40 +25,8 @@
>> # It provides the general basic services required by other DAL
>> # subcomponents.
>>
>> -ifdef CONFIG_X86
>> -dml_ccflags-$(CONFIG_CC_IS_GCC) := -mhard-float
>> -dml_ccflags := $(dml_ccflags-y) -msse
>> -endif
>> -
>> -ifdef CONFIG_PPC64
>> -dml_ccflags := -mhard-float -maltivec
>> -endif
>
> And altivec is enabled in the flags there.
>
> That doesn't match your implementation for powerpc in patch 7, which
> only deals with float.
>
> I suspect the AMD driver actually doesn't need altivec enabled, but I
> don't know that for sure. It compiles without it, but I don't have a GPU
> to actually test. I've added Timothy on Cc who added the support for
> powerpc to the driver originally, hopefully he has a test system.
I tested this series on a POWER9 system with an AMD Radeon RX 6400 GPU (which
requires this FPU code to initialize), and got functioning graphics output.
> Anyway if that's true that it doesn't need altivec we should probably do
> a lead-up patch that drops altivec from the AMD driver explicitly, eg.
> as below.
That makes sense to me. Do you want to provide your Signed-off-by so I can send
this patch with your authorship?
Regards,
Samuel
> cheers
>
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> index 4ae4720535a5..0de16796466b 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> @@ -92,11 +92,7 @@ void dc_fpu_begin(const char *function_name, const int line)
> #if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
> kernel_fpu_begin();
> #elif defined(CONFIG_PPC64)
> - if (cpu_has_feature(CPU_FTR_VSX_COMP))
> - enable_kernel_vsx();
> - else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP))
> - enable_kernel_altivec();
> - else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
> + if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
> enable_kernel_fp();
> #elif defined(CONFIG_ARM64)
> kernel_neon_begin();
> @@ -125,11 +121,7 @@ void dc_fpu_end(const char *function_name, const int line)
> #if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
> kernel_fpu_end();
> #elif defined(CONFIG_PPC64)
> - if (cpu_has_feature(CPU_FTR_VSX_COMP))
> - disable_kernel_vsx();
> - else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP))
> - disable_kernel_altivec();
> - else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
> + if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
> disable_kernel_fp();
> #elif defined(CONFIG_ARM64)
> kernel_neon_end();
> diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> index 6042a5a6a44f..554c39024a40 100644
> --- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> @@ -31,7 +31,7 @@ dml_ccflags := $(dml_ccflags-y) -msse
> endif
>
> ifdef CONFIG_PPC64
> -dml_ccflags := -mhard-float -maltivec
> +dml_ccflags := -mhard-float
> endif
>
> ifdef CONFIG_ARM64
> diff --git a/drivers/gpu/drm/amd/display/dc/dml2/Makefile b/drivers/gpu/drm/amd/display/dc/dml2/Makefile
> index acff3449b8d7..7b51364084b5 100644
> --- a/drivers/gpu/drm/amd/display/dc/dml2/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dml2/Makefile
> @@ -30,7 +30,7 @@ dml2_ccflags := $(dml2_ccflags-y) -msse
> endif
>
> ifdef CONFIG_PPC64
> -dml2_ccflags := -mhard-float -maltivec
> +dml2_ccflags := -mhard-float
> endif
>
> ifdef CONFIG_ARM64
