Re: [PATCH -stable] drm/amdgpu/display: drop DCN support for aarch64

[Greg KH <greg@kroah.com>]

On Thu, Jan 21, 2021 at 10:20:40AM +0100, Ard Biesheuvel wrote:
> From: Alex Deucher <alexander.deucher@amd.com>
> 
> commit c241ed2f0ea549c18cff62a3708b43846b84dae3 upstream.
> 
> >From Ard:
> 
> "Simply disabling -mgeneral-regs-only left and right is risky, given that
> the standard AArch64 ABI permits the use of FP/SIMD registers anywhere,
> and GCC is known to use SIMD registers for spilling, and may invent
> other uses of the FP/SIMD register file that have nothing to do with the
> floating point code in question. Note that putting kernel_neon_begin()
> and kernel_neon_end() around the code that does use FP is not sufficient
> here, the problem is in all the other code that may be emitted with
> references to SIMD registers in it.
> 
> So the only way to do this properly is to put all floating point code in
> a separate compilation unit, and only compile that unit with
> -mgeneral-regs-only."
> 
> Disable support until the code can be properly refactored to support this
> properly on aarch64.
> 
> Acked-by: Will Deacon <will@kernel.org>
> Reported-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> [ardb: backport to v5.10 by reverting c38d444e44badc55 instead]
> Acked-by: Alex Deucher <alexander.deucher@amd.com> # v5.10 backport
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> The original commit does not apply cleanly to v5.10, as it reverts a
> combination of patches, some of which are not present in v5.10.
> 
> This patch is a straight revert of c38d444e44badc55, which is the only
> change that needs to be backed out from v5.10, and amounts to the same
> thing as the original mainline commit.

Now queued up, thanks.

greg k-h