Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757403Ab3JJW3H (ORCPT ); Thu, 10 Oct 2013 18:29:07 -0400 Received: from mail-ie0-f180.google.com ([209.85.223.180]:57435 "EHLO mail-ie0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751675Ab3JJW3F (ORCPT ); Thu, 10 Oct 2013 18:29:05 -0400 MIME-Version: 1.0 In-Reply-To: <5257288E.6000704@wwwdotorg.org> References: <1380904635-18113-1-git-send-email-acourbot@nvidia.com> <1380904635-18113-2-git-send-email-acourbot@nvidia.com> <5257288E.6000704@wwwdotorg.org> From: Alexandre Courbot Date: Thu, 10 Oct 2013 15:28:43 -0700 Message-ID: Subject: Re: [PATCH v7 1/5] ARM: add basic support for Trusted Foundations To: Stephen Warren Cc: Olof Johansson , Alexandre Courbot , Russell King , Tomasz Figa , Dave Martin , Arnd Bergmann , Kevin Hilman , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-tegra@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2442 Lines: 48 On Thu, Oct 10, 2013 at 3:22 PM, Stephen Warren wrote: > On 10/10/2013 02:58 PM, Alexandre Courbot wrote: >> On Wed, Oct 9, 2013 at 4:47 PM, Olof Johansson wrote: >>> On Fri, Oct 4, 2013 at 9:37 AM, Alexandre Courbot wrote: > ... >>> But do we really need to panic here? It's a PITA to debug since it'll >>> be a very early panic. I'd rather have the system log errors in dmesg >>> but continue booting with one cpu. >> >> Actually the first version of this series continued on one CPU if TF >> support was missing (as secondary CPUs would simply fail to boot), but >> IIRC Stephen advocated for the current behavior (panic) instead. I >> agree such an early panic is hard to debug, especially considering >> that most devices using TF (Tegra retail devices) do not even feature >> a serial port. >> >> On the other hand, if we continue booting in these conditions the >> system freezes as soon as cpuidle kicks in, so we won't be going very >> far anyway. However the console is up when it happens. >> >> Maybe if there is a way to disable the kernel features TF is supposed >> to manage (SMP & cpuidle at the moment) when registration fails, the >> system could continue more gracefully (even if on one leg) and warn >> the user about this condition. Stephen, can I have your thoughts on >> this? > > If we can disable the features that rely on TF/secure-mode when support > is missing, then doing that rather than panic is fine. We do something > similar for PCIe on Tegra20, where LP2 cpuidle state must be disabled or > PCIe interrupts won't work. > > I would be inclined to merge the patch as-is right now, since it's only > enabling a new feature that won't see any regressions due to this panic, > and then add the disable-other-features with a separate patch/series > later. Does that seem reasonable? According to Olof we should also be moving the DT node under /firmware, so I guess another revision is in order to at least get this part right. 3.12 also added a powered-down cpuidle state for Tegra which freezes the system if TF is enabled as the firmware driver does not support idle yet, but this can be fixed later. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/