drm/amd/display: only use hard-float, not altivec on powerpc

The compiler flags enable altivec, but that is not required; hard-float is
sufficient for the code to build and function.

Drop altivec from the compiler flags and adjust the enable/disable code to
only enable FPU use.

Link: https://lkml.kernel.org/r/20240329072441.591471-13-samuel.holland@sifive.com
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com> 
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: WANG Xuerui <git@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: mpe

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();

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

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