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

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Message-ID: <b89b2e50-54c6-4ff8-ab52-c8f370ff9e4c@roeck-us.net>
Date: Fri, 24 May 2024 11:23:51 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Alex Deucher <alexdeucher@...il.com>
Cc: Samuel Holland <samuel.holland@...ive.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 linux-arm-kernel@...ts.infradead.org, x86@...nel.org,
 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 5/24/24 06:18, Alex Deucher wrote:
> On Fri, May 24, 2024 at 9:17 AM Alex Deucher <alexdeucher@...il.com> wrote:
>>
>> On Fri, May 24, 2024 at 5:16 AM Guenter Roeck <linux@...ck-us.net> wrote:
>>>
>>> Hi,
>>>
>>> On Fri, Mar 29, 2024 at 12:18:28AM -0700, 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>
>>>> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
>>>
>>> With this patch in the mainline kernel, I get the following build error
>>> when trying to build powerpc:ppc32_allmodconfig.
>>>
>>> powerpc64-linux-ld: drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o uses hard float, drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_helpers.o uses soft float
>>> powerpc64-linux-ld: failed to merge target specific data of file drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o
>>>
>>> [ repeated many times ]
>>>
>>> The problem is no longer seen after reverting this patch.
>>
>> Should be fixed with this patch:
>> https://gitlab.freedesktop.org/agd5f/linux/-/commit/5f56be33f33dd1d50b9433f842c879a20dc00f5b
>> Will pull it into my -fixes branch.
>>
> 
> Nevermind, this is something else.
> 

mdgpu_dm_helpers.o is built with -msoft-float, display_mode_lib.o is built
with -mhard-float.

-msoft-float is from

arch/powerpc/Makefile:KBUILD_CFLAGS     += $(CC_FLAGS_NO_FPU)

-mhard-float is from

drivers/gpu/drm/amd/display/dc/dml/Makefile:dml_ccflags := $(CC_FLAGS_FPU)
drivers/gpu/drm/amd/display/dc/dml/Makefile:dml_rcflags := $(CC_FLAGS_NO_FPU)
drivers/gpu/drm/amd/display/dc/dml2/Makefile:dml2_ccflags := $(CC_FLAGS_FPU)
drivers/gpu/drm/amd/display/dc/dml2/Makefile:dml2_rcflags := $(CC_FLAGS_NO_FPU)

Unfortunately I have no idea know how to resolve this.

Guenter