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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B0AD9C433EF for ; Tue, 26 Jul 2022 00:56:42 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4LsJQK1ZdVz3bpr for ; Tue, 26 Jul 2022 10:56:41 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=kWgG78BP; dkim-atps=neutral Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4LsJPh3Fxgz3bYS for ; Tue, 26 Jul 2022 10:56:08 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=kWgG78BP; dkim-atps=neutral Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4LsJPh01Psz4x1T; Tue, 26 Jul 2022 10:56:07 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1658796968; bh=XM/sSLZCdmxU7N0ibsdjeo384f6+QLdmjSl5hrtE3HY=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=kWgG78BPwfOqjitCUhFJ1j7aQuatzG1Kzsf+7936A1WLUoNMph3bVIxIlABiTDJEJ hIIcGB/y8AFSlwe/+vhMtJcBEakfJHeQb/EPEh1G7QM8Fj1g7kmD4E4rDvBAscAEEQ Y9m7YoapBqwumAnrkXpPVFp4iTJcszdtuCXUjKZ3zAyIkxhYTxrIpZQ+9viWvCIJZN Lo+0ODKIoi8+wOoWZGyX2w81RnbtPvoDX+kaetTWOCl8t08KBgIfEZU4r9ji6GmqBD XC9xzCTHZvgPJML2QJUKrzkpJdrABgL2gtRQwE/S/p+qpY1A+EQDJrveHxPMK7Qwkp zoGf02DW07bSw== From: Michael Ellerman To: Linus Torvalds Subject: Re: [PATCH] drm/amdgpu: Re-enable DCN for 64-bit powerpc In-Reply-To: References: <20220725123918.1903255-1-mpe@ellerman.id.au> Date: Tue, 26 Jul 2022 10:56:07 +1000 Message-ID: <87k080bsk8.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dan@danny.cz, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, tpearson@raptorengineering.com, alexdeucher@gmail.com, linuxppc-dev@lists.ozlabs.org, linux@roeck-us.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Linus Torvalds writes: > On Mon, Jul 25, 2022 at 5:39 AM Michael Ellerman wrote: >> >> Further digging shows that the build failures only occur with compilers >> that default to 64-bit long double. > > Where the heck do we have 'long double' things anywhere in the kernel? There's one or two uses, but not in any code that's relevant to this issue AFAICS. > I tried to grep for it, and failed miserably. I found some constants > that would qualify, but they were in the v4l colorspaces-details.rst > doc file. > > Strange. It doesn't seem to matter if you use long double or not. It's just that if the long double size is 64-bits the linker refuses to link a mixture of soft/hard-float objects. The 64-bit ABI says long double is 128-bits, so the compilers that are using 64-bit long double are either not built correctly, or we are not passing the correct flags to them. There's an -mlong-double-128 flag which we can pass at build time which seems to do the right thing, I will probably add that to the kernel CFLAGS, but I want that to get a bit more testing. cheers