From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olof Johansson Subject: Re: [PATCH] ARM: tegra: Fix suspend hang on Tegra124 Chromebooks Date: Tue, 22 Dec 2015 15:42:03 -0800 Message-ID: <20151222234203.GA28181@localhost> References: <1449570409-30244-1-git-send-email-jonathanh@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1449570409-30244-1-git-send-email-jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jon Hunter Cc: Stephen Warren , Thierry Reding , Alexandre Courbot , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org On Tue, Dec 08, 2015 at 10:26:49AM +0000, Jon Hunter wrote: > Enabling CPUFreq support for Tegra124 Chromebooks is causing the Tegra124 > to hang when resuming from suspend. > > When CPUFreq is enabled, the CPU clock is changed from the PLLX clock to > the DFLL clock during kernel boot. When resuming from suspend the CPU > clock is temporarily changed back to the PLLX clock before switching back > to the DFLL. If the DFLL is operating at a much lower frequency than the > PLLX when we enter suspend, and so the CPU voltage rail is at a voltage > too low for the CPUs to operate at the PLLX frequency, then the device > will hang. > > Please note that the PLLX is used in the resume sequence to switch the CPU > clock from the very slow 32K clock to a faster clock during early resume > to speed up the resume sequence before the DFLL is resumed. > > Ideally, we should fix this by setting the suspend frequency so that it > matches the PLLX frequency, however, that would be a bigger change. For > now simply disable CPUFreq support for Tegra124 Chromebooks to avoid the > hang when resuming from suspend. > > Fixes: 9a0baee960a7 ("ARM: tegra: Enable CPUFreq support for Tegra124 > Chromebooks") > > Signed-off-by: Jon Hunter > --- > > Please note that this fix is required for v4.4 Since I saw this mentioned on IRC, I applied it directly to the arm-soc fixes branch. Thanks, -Olof