Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753233AbcD0HZN (ORCPT ); Wed, 27 Apr 2016 03:25:13 -0400 Received: from mail.kernel.org ([198.145.29.136]:37251 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753161AbcD0HZL (ORCPT ); Wed, 27 Apr 2016 03:25:11 -0400 Date: Wed, 27 Apr 2016 15:24:54 +0800 From: Shawn Guo To: Dong Aisheng Cc: Lucas Stach , Michael Turquette , Stephen Boyd , "linux-kernel@vger.kernel.org" , Stefan Agner , 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 Message-ID: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2199 Lines: 53 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. Shawn