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

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Date:   Thu, 14 Jul 2022 10:20:28 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Alex Deucher <alexdeucher@...il.com>,
        Harry Wentland <harry.wentland@....com>
Cc:     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

On 7/14/22 09:29, Alex Deucher wrote:
> 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

"enagine". Outch.

Anyway, thanks for applying.

Guenter

>>> 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
>>