Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752685AbcD0C5Y (ORCPT ); Tue, 26 Apr 2016 22:57:24 -0400 Received: from mail-qg0-f68.google.com ([209.85.192.68]:35485 "EHLO mail-qg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751710AbcD0C5W (ORCPT ); Tue, 26 Apr 2016 22:57:22 -0400 MIME-Version: 1.0 In-Reply-To: <20160427015835.GE30692@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> Date: Wed, 27 Apr 2016 10:57:21 +0800 Message-ID: Subject: Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled From: Dong Aisheng To: Shawn Guo 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" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1727 Lines: 49 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. Regards Dong Aisheng > Shawn