From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9B89C43334 for ; Mon, 25 Jul 2022 15:46:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235110AbiGYPqJ (ORCPT ); Mon, 25 Jul 2022 11:46:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234946AbiGYPqH (ORCPT ); Mon, 25 Jul 2022 11:46:07 -0400 Received: from redcrew.org (redcrew.org [37.157.195.192]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03B561024 for ; Mon, 25 Jul 2022 08:46:03 -0700 (PDT) Received: from server.danny.cz (85-71-161-19.rce.o2.cz [85.71.161.19]) by redcrew.org (Postfix) with ESMTP id E77F4A0C; Mon, 25 Jul 2022 17:46:00 +0200 (CEST) Received: from talos.danny.cz (unknown [IPv6:2001:470:5c11:160:47df:83f6:718e:218]) by server.danny.cz (Postfix) with SMTP id 1CF5211AA3A; Mon, 25 Jul 2022 17:46:00 +0200 (CEST) Date: Mon, 25 Jul 2022 17:45:59 +0200 From: Dan =?UTF-8?B?SG9yw6Fr?= To: Michael Ellerman Cc: , alexdeucher@gmail.com, amd-gfx@lists.freedesktop.org, linux@roeck-us.net, , , tpearson@raptorengineering.com Subject: Re: [PATCH] drm/amdgpu: Re-enable DCN for 64-bit powerpc Message-Id: <20220725174559.e71243fa54b48fc2183385be@danny.cz> In-Reply-To: <20220725123918.1903255-1-mpe@ellerman.id.au> References: <20220725123918.1903255-1-mpe@ellerman.id.au> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; powerpc64le-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 25 Jul 2022 22:39:18 +1000 Michael Ellerman wrote: > Commit d11219ad53dc ("amdgpu: disable powerpc support for the newer > display engine") disabled the DCN driver for all of powerpc due to > unresolved build failures with some compilers. > > Further digging shows that the build failures only occur with compilers > that default to 64-bit long double. > > Both the ppc64 and ppc64le ABIs define long double to be 128-bits, but > there are compilers in the wild that default to 64-bits. The compilers > provided by the major distros (Fedora, Ubuntu) default to 128-bits and > are not affected by the build failure. > > There is a compiler flag to force 128-bit long double, which may be the > correct long term fix, but as an interim fix only allow building the DCN > driver if long double is 128-bits by default. > > The bisection in commit d11219ad53dc must have gone off the rails at > some point, the build failure occurs all the way back to the original > commit that enabled DCN support on powerpc, at least with some > toolchains. > > Depends-on: d11219ad53dc ("amdgpu: disable powerpc support for the newer display engine") > Fixes: 16a9dea110a6 ("amdgpu: Enable initial DCN support on POWER") > Signed-off-by: Michael Ellerman > Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2100 LGTM Reviewed-by: Dan Horák Dan > --- > arch/powerpc/Kconfig | 4 ++++ > drivers/gpu/drm/amd/display/Kconfig | 2 +- > 2 files changed, 5 insertions(+), 1 deletion(-) > > Alex, are you OK if I take this via the powerpc tree for v5.19? > > cheers > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 7aa12e88c580..287cc2d4a4b3 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -281,6 +281,10 @@ config PPC > # Please keep this list sorted alphabetically. > # > > +config PPC_LONG_DOUBLE_128 > + depends on PPC64 > + def_bool $(success,test "$(shell,echo __LONG_DOUBLE_128__ | $(CC) -E -P -)" = 1) > + > config PPC_BARRIER_NOSPEC > bool > default y > diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig > index 0ba0598eba20..ec6771e87e73 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 && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS) > + select DRM_AMD_DC_DCN if (X86 || PPC_LONG_DOUBLE_128) && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS) > help > Choose this option if you want to use the new display engine > support for AMDGPU. This adds required support for Vega and > -- > 2.35.3 >