From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH v2] clk: tegra: Use readl_relaxed_poll_timeout_atomic in tegra210_clock_init Date: Fri, 20 Oct 2017 11:20:24 +0100 Message-ID: <731a934a-4e78-b96d-239f-14cf83079605@nvidia.com> References: <1505502613-11801-1-git-send-email-nicoleotsuka@gmail.com> <20171019092919.GA7252@Asurada> <20171019094422.GI9005@ulmo> <20171019184223.GA7415@Asurada-Nvidia> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20171019184223.GA7415@Asurada-Nvidia> Content-Language: en-US Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Nicolin Chen , Thierry Reding Cc: sboyd-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, pdeschrijver-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mturquette-rdvid1DuHRBWk0Htik3J/w@public.gmane.org, pgaikwad-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org List-Id: linux-tegra@vger.kernel.org On 19/10/17 19:42, Nicolin Chen wrote: > On Thu, Oct 19, 2017 at 11:44:22AM +0200, Thierry Reding wrote: >>>> Below is the call trace of tegra210_init_pllu() function: >>>> start_kernel() >>>> -> time_init() >>>> --> of_clk_init() >>>> ---> tegra210_clock_init() >>>> ----> tegra210_pll_init() >>>> -----> tegra210_init_pllu() > >> I'm wondering why we're not seeing a splat for this. Usually the kernel >> will warn if you sleep during atomic context. Does this mean we're just >> not hitting that case? > > Yes. > >> readx_poll_timeout() has a might_sleep_if(), and >> therefore it should always cause the splat. > > That's true as long as CONFIG_DEBUG_ATOMIC_SLEEP is enabled locally. > >> Any ideas why this has gone unnoticed for all this time? > > We can see in the tegra210_init_pllu() function that it'll not call > tegra210_enable_pllu() if pllu is already enabled (by bootloader). I was thinking that same and so I clobbered the PLLU enable bit with u-boot, however, then the kernel appears to hang on boot when enabling the PLL. So although this is probably a separate issue, I am curious if you have booted the mainline with the PLLU disabled? Cheers Jon -- nvpublic From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752869AbdJTKWb (ORCPT ); Fri, 20 Oct 2017 06:22:31 -0400 Received: from hqemgate15.nvidia.com ([216.228.121.64]:2768 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751967AbdJTKW3 (ORCPT ); Fri, 20 Oct 2017 06:22:29 -0400 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Fri, 20 Oct 2017 03:22:19 -0700 Subject: Re: [PATCH v2] clk: tegra: Use readl_relaxed_poll_timeout_atomic in tegra210_clock_init To: Nicolin Chen , Thierry Reding CC: , , , , , , References: <1505502613-11801-1-git-send-email-nicoleotsuka@gmail.com> <20171019092919.GA7252@Asurada> <20171019094422.GI9005@ulmo> <20171019184223.GA7415@Asurada-Nvidia> From: Jon Hunter Message-ID: <731a934a-4e78-b96d-239f-14cf83079605@nvidia.com> Date: Fri, 20 Oct 2017 11:20:24 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <20171019184223.GA7415@Asurada-Nvidia> X-Originating-IP: [10.21.132.144] X-ClientProxiedBy: UKMAIL101.nvidia.com (10.26.138.13) To UKMAIL101.nvidia.com (10.26.138.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/10/17 19:42, Nicolin Chen wrote: > On Thu, Oct 19, 2017 at 11:44:22AM +0200, Thierry Reding wrote: >>>> Below is the call trace of tegra210_init_pllu() function: >>>> start_kernel() >>>> -> time_init() >>>> --> of_clk_init() >>>> ---> tegra210_clock_init() >>>> ----> tegra210_pll_init() >>>> -----> tegra210_init_pllu() > >> I'm wondering why we're not seeing a splat for this. Usually the kernel >> will warn if you sleep during atomic context. Does this mean we're just >> not hitting that case? > > Yes. > >> readx_poll_timeout() has a might_sleep_if(), and >> therefore it should always cause the splat. > > That's true as long as CONFIG_DEBUG_ATOMIC_SLEEP is enabled locally. > >> Any ideas why this has gone unnoticed for all this time? > > We can see in the tegra210_init_pllu() function that it'll not call > tegra210_enable_pllu() if pllu is already enabled (by bootloader). I was thinking that same and so I clobbered the PLLU enable bit with u-boot, however, then the kernel appears to hang on boot when enabling the PLL. So although this is probably a separate issue, I am curious if you have booted the mainline with the PLLU disabled? Cheers Jon -- nvpublic