Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759970Ab2HXSVr (ORCPT ); Fri, 24 Aug 2012 14:21:47 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:45125 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754259Ab2HXSVo (ORCPT ); Fri, 24 Aug 2012 14:21:44 -0400 Date: Fri, 24 Aug 2012 19:21:33 +0100 From: Russell King - ARM Linux To: Bill Huang Cc: "'linux-tegra@vger.kernel.org'" , "'linux-kernel@vger.kernel.org'" , "'linux-arm-kernel@lists.infradead.org'" Subject: Re: Shutdown problem in SMP system happened on Tegra20 Message-ID: <20120824182133.GB18957@n2100.arm.linux.org.uk> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2214 Lines: 55 On Fri, Aug 24, 2012 at 04:23:39PM +0800, Bill Huang wrote: > When doing shutdown on Tegra20/Tegra30, we need to read/write PMIC > registers through I2C to perform the power off sequence. Unfortunately, > sometimes we'll fail to shutdown due to I2C timeout on Tegra20. And the > cause of the timeout is due to the CPU which I2C controller IRQ affined > to will have chance to be offlined without migrating all irqs affined > to it, so the following I2C transactions will fail (no any CPU will > handle that interrupt since then). > Some snippet of the shutdown codes: > > void kernel_power_off(void) > { > kernel_shutdown_prepare(SYSTEM_POWER_OFF); > : > disable_nonboot_cpus(); > : > machine_power_off(); > } > > void machine_power_off(void) > { > machine_shutdown(); > if (pm_power_off) > pm_power_off(); /* this is where we send I2C write to shutdown */ > } > > void machine_shutdown(void) > { > #ifdef CONFIG_SMP > smp_send_stop(); > #endif > } > > In "smp_send_stop()", it will send "IPI_CPU_STOPS" to offline other cpus except > current cpu (smp_processor_id()), however, current cpu will not always be cpu0 at > least at Tegra20, that said for example cpu1 might be the current cpu and cpu0 will > be offlined and this is the case why the I2C transaction will timeout. > > For normal case, "disable_nonboot_cpus()" call will disable all other Cpus except > cpu0, that means we won't hit the problem mentioned here since cpu0 will always be > the current cpu in the call "smp_send_stop", but the call to "disable_nonboot_cpus" > will happen only when "CONFIG_PM_SLEEP_SMP" is enabled which is not the case for > Tegra20/Tegra30, we don't support suspend yet so this can't be enabled. So what you're asking for is a feature to do what CONFIG_PM_SLEEP_SMP does, but without CONFIG_PM_SLEEP_SMP enabled? Why not just ensure that CONFIG_PM_SLEEP_SMP is enabled if your platform requires that the lowest CPU number be the CPU dealing with reboot? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/