Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753336AbcD0Haa (ORCPT ); Wed, 27 Apr 2016 03:30:30 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:52443 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753298AbcD0HaW (ORCPT ); Wed, 27 Apr 2016 03:30:22 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Wed, 27 Apr 2016 00:26:49 -0700 From: Stefan Agner To: Shawn Guo Cc: Dong Aisheng , Lucas Stach , Michael Turquette , Stephen Boyd , linux-kernel@vger.kernel.org, mingo@redhat.com, kernel@pengutronix.de, tglx@linutronix.de, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled In-Reply-To: <20160427072454.GJ30692@tiger> References: <1454107764-19876-1-git-send-email-stefan@agner.ch> <20160421034520.GA19965@shlinux2.ap.freescale.net> <20160426012341.GB8870@tiger> <1461663072.7839.17.camel@pengutronix.de> <20160427015835.GE30692@tiger> <20160427072454.GJ30692@tiger> Message-ID: <9caa5658ccaf6ad43b3a2f07606f944e@agner.ch> User-Agent: Roundcube Webmail/1.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2463 Lines: 60 On 2016-04-27 00:24, Shawn Guo wrote: > On Wed, Apr 27, 2016 at 10:57:21AM +0800, Dong Aisheng wrote: >> On Wed, Apr 27, 2016 at 9:58 AM, Shawn Guo wrote: >> > On Tue, Apr 26, 2016 at 07:27:03PM +0800, Dong Aisheng wrote: >> >> Shawn, >> >> What's your suggestion? >> > >> > I think this needs more discussion, and I just dropped Stefan's patch >> > from my tree. >> > >> > We need to firstly understand why this is happening. The .prepare hook >> > is defined to be non-atomic context, and so that we call sleep function >> > in there. We did everything right. Why are we getting the warning? If >> > I'm correct, this warning only happens on i.MX7D. Why is that? >> > >> >> Why Stefan's patch works (checking irqs_disabled()) is because during kernel >> time init, the irq is still not enabled. It fixes the issue indirectly. >> See: >> asmlinkage __visible void __init start_kernel(void) >> { >> /* >> * Set up the scheduler prior starting any interrupts (such as the >> * timer interrupt). Full topology setup happens at smp_init() >> * time - but meanwhile we still have a functioning scheduler. >> */ >> sched_init(); >> ............. >> time_init(); >> .............. >> WARN(!irqs_disabled(), "Interrupts were enabled early\n"); >> early_boot_irqs_disabled = false; >> local_irq_enable(); >> } >> >> The issue can only happen when PLL enable causes a schedule during >> imx_clock_init(). >> Not all PLL has this issue. >> The issue happens on MX7D pll_audio_main_clk/pll_video_main_clk >> which requires more delay time and cause usleep. >> Because clk framework does not support MX7D clock types (operation requires >> parents on), we simply enable all clocks in imx7d_clocks_init(). >> >> If apply my this patch series: >> https://lkml.org/lkml/2016/4/20/199 >> The issue can also be gone. > > Thanks for the info. It sounds like that we are fixing the problem in > the wrong place, i.e. clk_pllv3_prepare(). The function does nothing > wrong, since the .prepare hook is defined to be one that can sleep. If > we see sleep warning in a context calling clk_prepare(), that probably > means we shouldn't make the function call from that context. > According to the stack trace in the answer to Stephens question the call comes from imx7d_clocks_init. I doubt we can avoid that those clocks get enabled there... -- Stefan