From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3s31xz31bszDqQT for ; Tue, 2 Aug 2016 00:32:23 +1000 (AEST) Date: Mon, 1 Aug 2016 09:31:04 -0500 From: Segher Boessenkool To: Christophe Leroy Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Scott Wood , antoine.blangy@c-s.fr, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] powerpc/32: fix csum_partial_copy_generic() Message-ID: <20160801143103.GB1742@gate.crashing.org> References: <20160801125605.410371A23A2@localhost.localdomain> <20160801131505.GA1742@gate.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Aug 01, 2016 at 03:45:59PM +0200, Christophe Leroy wrote: > >>--- a/arch/powerpc/lib/checksum_32.S > >>+++ b/arch/powerpc/lib/checksum_32.S > >>@@ -127,7 +127,8 @@ _GLOBAL(csum_partial_copy_generic) > >> stw r7,12(r1) > >> stw r8,8(r1) > >> > >>- andi. r0,r4,1 /* is destination address even ? */ > >>+ rlwinm r0,r4,3,0x8 /* is destination address even ? */ > >>+ rlwnm r6,r6,r0,0,31 /* swap bytes for odd destination */ > >> cmplwi cr7,r0,0 > >> addic r12,r6,0 > >> addi r6,r4,-4 > > > >That does not "swap bytes"; it shifts the word up by 8 bits, instead. > >That may or may not do what is intended. > > Indeed it does what is intended, similar to what is done at the end of > the function: > > ... > beqlr+ cr7 > rlwinm r3,r3,8,0,31 /* swap bytes for odd destination */ > blr > > Should I fix the (both) comment(s) ? It's quite confusing comment, so yes please. The code is hard enough to understand as is! Segher