From mboxrd@z Thu Jan 1 00:00:00 1970 From: sudeep.holla@arm.com (Sudeep Holla) Date: Thu, 8 Jan 2015 06:29:04 +0000 Subject: [PATCH] drivers: cpuidle: don't initialize big.LITTLE driver if MCPM is unavailable Message-ID: <1420698544-10277-1-git-send-email-sudeep.holla@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org If big.LITTLE driver is initialized even when MCPM is unavailable, we get the below warning the first time cpu tries to enter deeper C-states. ------------[ cut here ]------------ WARNING: CPU: 4 PID: 0 at kernel/arch/arm/common/mcpm_entry.c:130 mcpm_cpu_suspend+0x6d/0x74() Modules linked in: CPU: 4 PID: 0 Comm: swapper/4 Not tainted 3.19.0-rc3-00007-gaf5a2cb1ad5c-dirty #11 Hardware name: ARM-Versatile Express [] (unwind_backtrace) from [] (show_stack+0x11/0x14) [] (show_stack) from [] (dump_stack+0x6d/0x78) [] (dump_stack) from [] (warn_slowpath_common+0x69/0x90) [] (warn_slowpath_common) from [] (warn_slowpath_null+0x17/0x1c) [] (warn_slowpath_null) from [] (mcpm_cpu_suspend+0x6d/0x74) [] (mcpm_cpu_suspend) from [] (bl_powerdown_finisher+0x21/0x24) [] (bl_powerdown_finisher) from [] (cpu_suspend_abort+0x1/0x14) [] (cpu_suspend_abort) from [<00000000>] ( (null)) ---[ end trace d098e3fd00000008 ]--- This patch fixes the issue by checking for the availability of MCPM before initializing the big.LITTLE cpuidle driver Signed-off-by: Sudeep Holla Cc: Lorenzo Pieralisi Cc: Daniel Lezcano Cc: "Rafael J. Wysocki" --- drivers/cpuidle/cpuidle-big_little.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/cpuidle/cpuidle-big_little.c b/drivers/cpuidle/cpuidle-big_little.c index e3e225fe6b45..40c34faffe59 100644 --- a/drivers/cpuidle/cpuidle-big_little.c +++ b/drivers/cpuidle/cpuidle-big_little.c @@ -182,6 +182,10 @@ static int __init bl_idle_init(void) */ if (!of_match_node(compatible_machine_match, root)) return -ENODEV; + + if (!mcpm_is_available()) + return -EUNATCH; + /* * For now the differentiation between little and big cores * is based on the part number. A7 cores are considered little -- 1.9.1