From mboxrd@z Thu Jan 1 00:00:00 1970 From: shawn.guo@linaro.org (Shawn Guo) Date: Thu, 30 Apr 2015 23:25:49 +0800 Subject: [PATCH] ARM: imx6: initialize CCM_CLPCR_LPM into RUN mode earlier In-Reply-To: References: <1430287119-5268-1-git-send-email-shawn.guo@linaro.org> Message-ID: <20150430152547.GC20956@dragon> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Apr 29, 2015 at 01:43:39PM -0700, Tyler Baker wrote: > On 28 April 2015 at 22:58, Shawn Guo wrote: > > Commit 4631960d26da ("ARM: imx6: set initial power mode in pm function") > > moves imx6_set_lpm() from clock init function into > > imx6_pm_common_init(). This causes a hang when cpuidle support is > > enabled. The reason for that is ARM core clock is shut down > > unexpectedly by WAIT mode. It happens with the following call stack: > > > > cpuidle_register_governor() > > cpuidle_switch_governor() > > cpuidle_uninstall_idle_handler() > > synchronize_sched() > > wait_rcu_gp() > > wait_for_completion() > > > > When wait_for_completion() is called as above, all cores are idle/WFI. > > Hence, the reset value of CCM_CLPCR_LPM - WAIT mode, will trigger a > > hardware shutdown of the ARM core clock. > > > > To fix the regression, we need to ensure that CCM_CLPCR_LPM is > > initialized into RUN mode earlier than cpuidle governor registration, > > which is a postcore_initcall. This patch creates function > > imx6_pm_ccm_init() to map CCM block and initialize CCM_CLPCR_LPM into > > RUN mode, and have the function called from machine .init_irq hook, > > which should be early enough. > > > > Reported-by: Kevin Hilman > > Fixes: 4631960d26da ("ARM: imx6: set initial power mode in pm function") > > Signed-off-by: Shawn Guo > > Tested-by: Tyler Baker > > I have applied this patch on top of next-20150429[1] and build/boot > tested it with the kernelci.org farm. With these results[2], I can > confirm the IMX6 boot regression reported is fixed by this patch. Thanks for testing, Tyler. I added your test tag to the patch. Shawn