linux-kernel - Re: [PATCH] drm/amd/display: Enable building new display engine with KCOV enabled

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Message-ID: <98b656f3-e506-90be-ebcc-898813051e74@amd.com>
Date:   Wed, 13 Jul 2022 16:02:58 -0400
From:   Harry Wentland <harry.wentland@....com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Alex Deucher <alexander.deucher@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Leo Li <sunpeng.li@....com>
Subject: Re: [PATCH] drm/amd/display: Enable building new display engine with
 KCOV enabled

On 2022-07-12 18:42, Guenter Roeck wrote:
> The new display engine uses floating point math, which is not supported
> by KCOV. Commit 9d1d02ff3678 ("drm/amd/display: Don't build DCN1 when kcov
> is enabled") tried to work around the problem by disabling
> CONFIG_DRM_AMD_DC_DCN if KCOV_INSTRUMENT_ALL and KCOV_ENABLE_COMPARISONS
> are enabled. The result is that KCOV can not be enabled on systems which
> require this display engine. A much simpler and less invasive solution is
> to disable KCOV selectively when compiling the display enagine while
> keeping it enabled for the rest of the kernel.
> 
> Fixes: 9d1d02ff3678 ("drm/amd/display: Don't build DCN1 when kcov is enabled")
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Leo Li <sunpeng.li@....com>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

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

Harry

> ---
>  drivers/gpu/drm/amd/display/Kconfig     | 2 +-
>  drivers/gpu/drm/amd/display/dc/Makefile | 3 +++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig
> index b4029c0d5d8c..96cbc87f7b6b 100644
> --- a/drivers/gpu/drm/amd/display/Kconfig
> +++ b/drivers/gpu/drm/amd/display/Kconfig
> @@ -6,7 +6,7 @@ config DRM_AMD_DC
>  	bool "AMD DC - Enable new display engine"
>  	default y
>  	select SND_HDA_COMPONENT if SND_HDA_CORE
> -	select DRM_AMD_DC_DCN if (X86 || PPC64) && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS)
> +	select DRM_AMD_DC_DCN if (X86 || PPC64)
>  	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/dc/Makefile b/drivers/gpu/drm/amd/display/dc/Makefile
> index b4eca0236435..b801973749d2 100644
> --- a/drivers/gpu/drm/amd/display/dc/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/Makefile
> @@ -26,6 +26,9 @@
>  DC_LIBS = basics bios dml clk_mgr dce gpio irq link virtual
>  
>  ifdef CONFIG_DRM_AMD_DC_DCN
> +
> +KCOV_INSTRUMENT := n
> +
>  DC_LIBS += dcn20
>  DC_LIBS += dsc
>  DC_LIBS += dcn10