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Message-ID: <4c8e63d6-ba33-47fe-8150-59eba8babf2d@sifive.com>
Date: Wed, 10 Apr 2024 20:11:04 -0500
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Subject: Re: [PATCH v4 13/15] drm/amd/display: Use ARCH_HAS_KERNEL_FPU_SUPPORT
To: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
 linux-arm-kernel@lists.infradead.org, x86@kernel.org,
 linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
 linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
 Christoph Hellwig <hch@lst.de>, loongarch@lists.linux.dev,
 amd-gfx@lists.freedesktop.org, Alex Deucher <alexander.deucher@amd.com>
References: <20240329072441.591471-1-samuel.holland@sifive.com>
 <20240329072441.591471-14-samuel.holland@sifive.com>
 <87wmp4oo3y.fsf@linaro.org> <75a37a4b-f516-40a3-b6b5-4aa1636f9b60@sifive.com>
 <87wmp4ogoe.fsf@linaro.org>
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From: Samuel Holland <samuel.holland@sifive.com>
In-Reply-To: <87wmp4ogoe.fsf@linaro.org>
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Hi Thiago,

On 2024-04-10 8:02 PM, Thiago Jung Bauermann wrote:
> Samuel Holland <samuel.holland@sifive.com> writes:
>> On 2024-04-10 5:21 PM, Thiago Jung Bauermann wrote:
>>>
>>> Unfortunately this patch causes build failures on arm with allyesconfig
>>> and allmodconfig. Tested with next-20240410.
> 
> <snip>
> 
>> In both cases, the issue is that the toolchain requires runtime support to
>> convert between `unsigned long long` and `double`, even when hardware FP is
>> enabled. There was some past discussion about GCC inlining some of these
>> conversions[1], but that did not get implemented.
> 
> Thank you for the explanation and the bugzilla reference. I added a
> comment there mentioning that the problem came up again with this patch
> series.
> 
>> The short-term fix would be to drop the `select ARCH_HAS_KERNEL_FPU_SUPPORT` for
>> 32-bit arm until we can provide these runtime library functions.
> 
> Does this mean that patch 2 in this series:
> 
> [PATCH v4 02/15] ARM: Implement ARCH_HAS_KERNEL_FPU_SUPPORT
> 
> will be dropped?

No, because later patches in the series (3, 6) depend on the definition of
CC_FLAGS_FPU from that patch. I will need to send a fixup patch unless I can
find a GPL-2 compatible implementation of the runtime library functions.

Regards,
Samuel