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

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Date:   Thu, 14 Jul 2022 12:29:45 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Harry Wentland <harry.wentland@....com>
Cc:     Guenter Roeck <linux@...ck-us.net>, Arnd Bergmann <arnd@...db.de>,
        Leo Li <sunpeng.li@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH] drm/amd/display: Enable building new display engine with
 KCOV enabled

Applied.  Thanks!

On Wed, Jul 13, 2022 at 4:03 PM Harry Wentland <harry.wentland@....com> wrote:
>
> 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
>