From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH] ARM: tegra: Fix suspend hang on Tegra124 Chromebooks Date: Wed, 23 Dec 2015 09:00:16 +0000 Message-ID: <567A62A0.1000809@nvidia.com> References: <1449570409-30244-1-git-send-email-jonathanh@nvidia.com> <20151222234203.GA28181@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20151222234203.GA28181@localhost> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Olof Johansson 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 22/12/15 23:42, Olof Johansson wrote: > 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! Cheers Jon