From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756182Ab2BALJt (ORCPT ); Wed, 1 Feb 2012 06:09:49 -0500 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:58250 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753999Ab2BALJs (ORCPT ); Wed, 1 Feb 2012 06:09:48 -0500 Date: Wed, 1 Feb 2012 11:08:36 +0000 From: Will Deacon To: Russell King - ARM Linux Cc: Peter De Schrijver , Stephen Warren , Gary King , Arnd Bergmann , "linux-kernel@vger.kernel.org" , "linux-tegra@vger.kernel.org" , Colin Cross , Olof Johansson , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v2 3/8] ARM: tegra: rework Tegra secondary CPU core bringup Message-ID: <20120201110836.GB3058@mudshark.cambridge.arm.com> References: <1328028051-24271-1-git-send-email-pdeschrijver@nvidia.com> <1328028051-24271-4-git-send-email-pdeschrijver@nvidia.com> <20120131225045.GE8338@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120131225045.GE8338@n2100.arm.linux.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 31, 2012 at 10:50:45PM +0000, Russell King - ARM Linux wrote: > On Tue, Jan 31, 2012 at 06:40:41PM +0200, Peter De Schrijver wrote: > > +#ifdef CONFIG_ARM_ERRATA_743622 > > + teq r6, #0x20 @ present in r2p0 > > + teqne r6, #0x21 @ present in r2p1 > > + teqne r6, #0x22 @ present in r2p2 > > + teqne r6, #0x27 @ present in r2p7 > > + teqne r6, #0x29 @ present in r2p9 > > Okay, so we have this errata in proc-v7.S, but only for p0..p2. If > it's also p7 and p9, then it shows that the errata in the kernel aren't > being actively maintained, and brings into question their worth. It looks like the errata document has been updated since I wrote the workaround in proc-v7.S (and new r2p* versions of the A9 have been released). The new document states that r2p* are affected, so we should update the workaround. > Plus, of course, we don't want platforms re-implementing the errata > in their own code if we're already implementing it somewhere in the > kernel. So, that's something which needs to be thought about. Indeed, that could become extremely confusing, especially when they start doing different things. > That's something that needs considering along side the whole 'what > to do about errata when running in non-secure mode' problem which > OMAP suffers from. My view is that the workarounds in the kernel are a good way to highlight which errata we consider to be important from Linux's point-of-view and also how to avoid them in practice. It's not always possible to apply them in the kernel at runtime (due to security constraints) but I think it's important to show what Linux expects. I'll go back through the errata document and check if any others have been updated besides this one. Will