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

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Date: Wed, 10 Apr 2024 22:02:09 -0300
From: Thiago Jung Bauermann <thiago.bauermann@...aro.org>
To: Samuel Holland <samuel.holland@...ive.com>
Cc: 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


Hello Samuel,

Thank you for the quick reply!

Samuel Holland <samuel.holland@...ive.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?

--
Thiago