linux-kernel - Re: [PATCH] drm/i915: remove always-defined CONFIG_AS

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Date:   Mon, 23 Mar 2020 13:24:01 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        intel-gfx@...ts.freedesktop.org,
        LKML <linux-kernel@...r.kernel.org>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/i915: remove always-defined CONFIG_AS_MOVNTDQA

On Sun, Mar 22, 2020 at 7:12 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> CONFIG_AS_MOVNTDQA was introduced by commit 0b1de5d58e19 ("drm/i915:
> Use SSE4.1 movntdqa to accelerate reads from WC memory").
>
> We raise the minimal supported binutils version from time to time.
> The last bump was commit 1fb12b35e5ff ("kbuild: Raise the minimum
> required binutils version to 2.21").

Indeed, I see 2.21 was released in 2010, and I see a commit modifying
existing support for movntdqa in 2008; it looks like these have been
supported for a while.  Thanks for this cleanup; the less we have to
invoke tools during make invocation, to lower the overhead of Kbuild.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> I confirmed the code in $(call as-instr,...) can be assembled by the
> binutils 2.21 assembler and also by Clang's integrated assembler.
>
> Remove CONFIG_AS_MOVNTDQA, which is always defined.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  drivers/gpu/drm/i915/Makefile      | 3 ---
>  drivers/gpu/drm/i915/i915_memcpy.c | 5 -----
>  2 files changed, 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index a1f2411aa21b..e559e53fc634 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -28,9 +28,6 @@ subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
>  CFLAGS_i915_pci.o = $(call cc-disable-warning, override-init)
>  CFLAGS_display/intel_fbdev.o = $(call cc-disable-warning, override-init)
>
> -subdir-ccflags-y += \
> -       $(call as-instr,movntdqa (%eax)$(comma)%xmm0,-DCONFIG_AS_MOVNTDQA)
> -
>  subdir-ccflags-y += -I$(srctree)/$(src)
>
>  # Please keep these build lists sorted!
> diff --git a/drivers/gpu/drm/i915/i915_memcpy.c b/drivers/gpu/drm/i915/i915_memcpy.c
> index fdd550405fd3..7b3b83bd5ab8 100644
> --- a/drivers/gpu/drm/i915/i915_memcpy.c
> +++ b/drivers/gpu/drm/i915/i915_memcpy.c
> @@ -35,7 +35,6 @@
>
>  static DEFINE_STATIC_KEY_FALSE(has_movntdqa);
>
> -#ifdef CONFIG_AS_MOVNTDQA
>  static void __memcpy_ntdqa(void *dst, const void *src, unsigned long len)
>  {
>         kernel_fpu_begin();
> @@ -93,10 +92,6 @@ static void __memcpy_ntdqu(void *dst, const void *src, unsigned long len)
>
>         kernel_fpu_end();
>  }
> -#else
> -static void __memcpy_ntdqa(void *dst, const void *src, unsigned long len) {}
> -static void __memcpy_ntdqu(void *dst, const void *src, unsigned long len) {}
> -#endif
>
>  /**
>   * i915_memcpy_from_wc: perform an accelerated *aligned* read from WC
> --
> 2.17.1
>
> --
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-- 
Thanks,
~Nick Desaulniers