From: gregory.clement@free-electrons.com (Gregory CLEMENT) Date: Mon, 10 Nov 2014 15:12:21 +0100 Subject: [PATCH 14/17] ARM: mvebu: synchronize secondary CPU clocks on resume In-Reply-To: <1414151970-6626-15-git-send-email-thomas.petazzoni@free-electrons.com> References: <1414151970-6626-1-git-send-email-thomas.petazzoni@free-electrons.com> <1414151970-6626-15-git-send-email-thomas.petazzoni@free-electrons.com> Message-ID: <5460C7C5.7060007@free-electrons.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Thomas, On 24/10/2014 13:59, Thomas Petazzoni wrote: > The Armada XP has multiple cores clocked by independent clocks. The > SMP startup code contains a function called set_secondary_cpus_clock() > called in armada_xp_smp_prepare_cpus() to ensure the clocks of the > secondary CPUs match the clock of the boot CPU. > > With the introduction of suspend/resume, this operation is no longer > needed when booting the system, but also when existing the suspend to > RAM state. Therefore this commit reworks a bit the logic: instead of > configuring the clock of all secondary CPUs in > armada_xp_smp_prepare_cpus(), we do it on a per-secondary CPU basis in > armada_xp_boot_secondary(), as this function gets called when existing > suspend to RAM for each secondary CPU. > > Since the function now only takes care of one CPU, we rename it from > set_secondary_cpus_clock() to set_secondary_cpu_clock(), and it looses > its __init marker, as it is now used beyond the system initialization. > > Note that we can't use smp_processor_id() directly, because when > exiting from suspend to RAM, the code is apparently executed with > preemption enabled, so smp_processor_id() is not happy (prints a > warning). We therefore switch to using get_cpu()/put_cpu(), even > though we pretty much have the guarantee that the code starting the > secondary CPUs is going to run on the boot CPU and will not be > migrated. > Acked-by: Gregory CLEMENT Thanks, Gregory > Signed-off-by: Thomas Petazzoni > --- > arch/arm/mach-mvebu/platsmp.c | 31 +++++++++++++++---------------- > 1 file changed, 15 insertions(+), 16 deletions(-) -- Gregory Clement, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com