From mboxrd@z Thu Jan 1 00:00:00 1970 From: khilman@kernel.org (Kevin Hilman) Date: Wed, 29 Apr 2015 09:35:28 -0700 Subject: [PATCH 05/11] ARM: imx6: set initial power mode in pm function In-Reply-To: <20150429060446.GA27573@dragon> (Shawn Guo's message of "Wed, 29 Apr 2015 14:04:58 +0800") References: <1430058672-9267-1-git-send-email-shawn.guo@linaro.org> <1430058672-9267-6-git-send-email-shawn.guo@linaro.org> <20150429060446.GA27573@dragon> Message-ID: <7h383ix57z.fsf@deeprootsystems.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Shawn Guo writes: > Hi Kevin, > > On Tue, Apr 28, 2015 at 11:42:48AM -0700, Kevin Hilman wrote: >> Hi Shawn, >> >> On Sun, Apr 26, 2015 at 7:31 AM, Shawn Guo wrote: >> > Rather than setting initial low-power mode in every single i.MX6 clock >> > initialization function, we should really do that in pm code. Let's >> > move imx6q_set_lpm(WAIT_CLOCKED) call into imx6_pm_common_init(). >> > >> > While at it, let's rename the function to imx6_set_lpm() since it's >> > actually common for all i.MX6 SoCs. >> > >> > Signed-off-by: Shawn Guo >> >> Some boot failures on imx6[1] (multi_v7_defconfig) were bisected down >> to this patch. A simple revert doesn't build, so I was unable tot >> test a direct revert. However, from the boot failures you can see >> that while multi_v7_defconfig boots fail, the imx_v6_v7_defconfig >> boots fine. > > This reminds me that cpuidle support is not turned on in > imx_v6_v7_defconfig. I will send a patch to enable it for testing > coverage. > >> Disabling CONFIG_CPU_IDLE in multi_v7_defconfig allows >> this to start booting again on my wandboard quad, so I think there is >> something wrong with the cpuidle changes. > > I just tracked down the issue, and sent a fix like below. Thanks for the quick fix. > The kernelci.org boot automation farm helps. Thanks. Glad it's useful. We're doing a build/boot test of your fix now, and will keep you updated. In the mean time..., > ----8<------------------------------- > From 056a5da1b56a057762eccd52b5b6b920c7f56b14 Mon Sep 17 00:00:00 2001 > From: Shawn Guo > Date: Wed, 29 Apr 2015 13:07:03 +0800 > Subject: [PATCH] ARM: imx6: initialize CCM_CLPCR_LPM into RUN mode earlier > > 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 ...I did a quick test of this locally on my wandboard-quad, and it's now booting with multi_v7_defconfig too. Tested-by: Kevin Hilman