From: Arnd Bergmann Subject: Re: [PATCH 2/8] dmaengine: mv_xor: add support for a38x command in descriptor mode Date: Tue, 12 May 2015 18:03:34 +0200 Message-ID: <3020836.4xH6fTICuR@wuerfel> References: <1431445063-20226-1-git-send-email-maxime.ripard@free-electrons.com> <4862159.g8Sk9nOiS2@wuerfel> <20150512175431.378c346e@free-electrons.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: Thomas Petazzoni , Lior Amsalem , Andrew Lunn , Jason Cooper , Vinod Koul , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, "David S. Miller" , Thomas Petazzoni , linux-crypto@vger.kernel.org, Gregory Clement , Herbert Xu , Maxime Ripard , Dan Williams , Sebastian Hesselbarth To: linux-arm-kernel@lists.infradead.org Return-path: Received: from mout.kundenserver.de ([212.227.17.10]:61325 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933149AbbELQEa (ORCPT ); Tue, 12 May 2015 12:04:30 -0400 In-Reply-To: <20150512175431.378c346e@free-electrons.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Tuesday 12 May 2015 17:54:31 Thomas Petazzoni wrote: > Dear Arnd Bergmann, > > On Tue, 12 May 2015 17:49:08 +0200, Arnd Bergmann wrote: > > > Using > > > > if (IS_ENABLED(__BIG_ENDIAN)) > > > > here would make it more readable by avoiding the #if. Alternatively, > > you could leave the XOR_DESCRIPTOR_SWAP flag disabled and just swap > > the descriptors manually like a lot of other drivers do. You have > > to swap the mmio accesses anywya. > > Agreed on IS_ENABLED(). However, I don't understand the comment about > the need to swap mmio accesses? We're using readl_relaxed() / > writel_relaxed(), and they do the swapping already. Am I missing > something? > Sorry for being unclear. This was exactly my point: readl_relaxed() has to do swaps internally, and you can also do swaps when accessing the descriptor in memory. Arnd