linux-kernel - Re: [PATCH v4 13/15] drm/amd/display: Use ARCH_HAS_KERNEL_FPU

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Message-ID: <958149a4-f5f5-4963-9af8-12e2a672733d@amd.com>
Date: Tue, 30 Apr 2024 13:29:06 -0400
From: Harry Wentland <harry.wentland@....com>
To: Samuel Holland <samuel.holland@...ive.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 linux-arm-kernel@...ts.infradead.org, x86@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
 Christoph Hellwig <hch@....de>, loongarch@...ts.linux.dev,
 amd-gfx@...ts.freedesktop.org, Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH v4 13/15] drm/amd/display: Use ARCH_HAS_KERNEL_FPU_SUPPORT



On 2024-03-29 03:18, Samuel Holland wrote:
> 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.
> 
> Acked-by: Alex Deucher <alexander.deucher@....com>
> Reviewed-by: Christoph Hellwig <hch@....de>

Really nice set of changes.

Acked-by: Harry Wentland <harry.wentland@....com>

Harry

> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
> ---
> 
> (no changes since v2)
> 
> Changes in v2:
>  - Split altivec removal to a separate patch
>  - Use linux/fpu.h instead of asm/fpu.h in consumers
> 
>  drivers/gpu/drm/amd/display/Kconfig           |  2 +-
>  .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    | 27 ++------------
>  drivers/gpu/drm/amd/display/dc/dml/Makefile   | 36 ++-----------------
>  drivers/gpu/drm/amd/display/dc/dml2/Makefile  | 36 ++-----------------
>  4 files changed, 7 insertions(+), 94 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig
> index 901d1961b739..5fcd4f778dc3 100644
> --- a/drivers/gpu/drm/amd/display/Kconfig
> +++ b/drivers/gpu/drm/amd/display/Kconfig
> @@ -8,7 +8,7 @@ config DRM_AMD_DC
>  	depends on BROKEN || !CC_IS_CLANG || ARM64 || RISCV || SPARC64 || X86_64
>  	select SND_HDA_COMPONENT if SND_HDA_CORE
>  	# !CC_IS_CLANG: https://github.com/ClangBuiltLinux/linux/issues/1752
> -	select DRM_AMD_DC_FP if (X86 || LOONGARCH || (PPC64 && ALTIVEC) || (ARM64 && KERNEL_MODE_NEON && !CC_IS_CLANG))
> +	select DRM_AMD_DC_FP if ARCH_HAS_KERNEL_FPU_SUPPORT && (!ARM64 || !CC_IS_CLANG)
>  	help
>  	  Choose this option if you want to use the new display engine
>  	  support for AMDGPU. This adds required support for Vega and
> 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 0de16796466b..e46f8ce41d87 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> @@ -26,16 +26,7 @@
>  
>  #include "dc_trace.h"
>  
> -#if defined(CONFIG_X86)
> -#include <asm/fpu/api.h>
> -#elif defined(CONFIG_PPC64)
> -#include <asm/switch_to.h>
> -#include <asm/cputable.h>
> -#elif defined(CONFIG_ARM64)
> -#include <asm/neon.h>
> -#elif defined(CONFIG_LOONGARCH)
> -#include <asm/fpu.h>
> -#endif
> +#include <linux/fpu.h>
>  
>  /**
>   * DOC: DC FPU manipulation overview
> @@ -87,16 +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_FPU_UNAVAILABLE))
> -			enable_kernel_fp();
> -#elif defined(CONFIG_ARM64)
> -		kernel_neon_begin();
> -#endif
>  	}
>  
>  	TRACE_DCN_FPU(true, function_name, line, depth);
> @@ -118,14 +102,7 @@ void dc_fpu_end(const char *function_name, const int line)
>  
>  	depth = __this_cpu_dec_return(fpu_recursion_depth);
>  	if (depth == 0) {
> -#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
>  		kernel_fpu_end();
> -#elif defined(CONFIG_PPC64)
> -		if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
> -			disable_kernel_fp();
> -#elif defined(CONFIG_ARM64)
> -		kernel_neon_end();
> -#endif
>  	} else {
>  		WARN_ON_ONCE(depth < 0);
>  	}
> diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> index 59d3972341d2..a94b6d546cd1 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 := $(dml_ccflags-y) -msse
> -endif
> -
> -ifdef CONFIG_PPC64
> -dml_ccflags := -mhard-float
> -endif
> -
> -ifdef CONFIG_ARM64
> -dml_rcflags := -mgeneral-regs-only
> -endif
> -
> -ifdef CONFIG_LOONGARCH
> -dml_ccflags := -mfpu=64
> -dml_rcflags := -msoft-float
> -endif
> -
> -ifdef CONFIG_CC_IS_GCC
> -ifneq ($(call gcc-min-version, 70100),y)
> -IS_OLD_GCC = 1
> -endif
> -endif
> -
> -ifdef CONFIG_X86
> -ifdef IS_OLD_GCC
> -# Stack alignment mismatch, proceed with caution.
> -# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
> -# (8B stack alignment).
> -dml_ccflags += -mpreferred-stack-boundary=4
> -else
> -dml_ccflags += -msse2
> -endif
> -endif
> +dml_ccflags := $(CC_FLAGS_FPU)
> +dml_rcflags := $(CC_FLAGS_NO_FPU)
>  
>  ifneq ($(CONFIG_FRAME_WARN),0)
>  ifeq ($(filter y,$(CONFIG_KASAN)$(CONFIG_KCSAN)),y)
> diff --git a/drivers/gpu/drm/amd/display/dc/dml2/Makefile b/drivers/gpu/drm/amd/display/dc/dml2/Makefile
> index 7b51364084b5..4f6c804a26ad 100644
> --- a/drivers/gpu/drm/amd/display/dc/dml2/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dml2/Makefile
> @@ -24,40 +24,8 @@
>  #
>  # Makefile for dml2.
>  
> -ifdef CONFIG_X86
> -dml2_ccflags-$(CONFIG_CC_IS_GCC) := -mhard-float
> -dml2_ccflags := $(dml2_ccflags-y) -msse
> -endif
> -
> -ifdef CONFIG_PPC64
> -dml2_ccflags := -mhard-float
> -endif
> -
> -ifdef CONFIG_ARM64
> -dml2_rcflags := -mgeneral-regs-only
> -endif
> -
> -ifdef CONFIG_LOONGARCH
> -dml2_ccflags := -mfpu=64
> -dml2_rcflags := -msoft-float
> -endif
> -
> -ifdef CONFIG_CC_IS_GCC
> -ifeq ($(call cc-ifversion, -lt, 0701, y), y)
> -IS_OLD_GCC = 1
> -endif
> -endif
> -
> -ifdef CONFIG_X86
> -ifdef IS_OLD_GCC
> -# Stack alignment mismatch, proceed with caution.
> -# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
> -# (8B stack alignment).
> -dml2_ccflags += -mpreferred-stack-boundary=4
> -else
> -dml2_ccflags += -msse2
> -endif
> -endif
> +dml2_ccflags := $(CC_FLAGS_FPU)
> +dml2_rcflags := $(CC_FLAGS_NO_FPU)
>  
>  ifneq ($(CONFIG_FRAME_WARN),0)
>  ifeq ($(filter y,$(CONFIG_KASAN)$(CONFIG_KCSAN)),y)