| Message ID | 20230919092850.1940729-2-mark.rutland@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Remove cpus_have_const_cap() | expand |
On Tue, 19 Sep 2023 10:28:14 +0100, Mark Rutland <mark.rutland@arm.com> wrote: > > We attempt to initialize each CPU's arch_timer event stream in > arch_timer_evtstrm_enable(), which we call from the > arch_timer_starting_cpu() cpu hotplug callback which is registered early > in boot. As this is registered before we initialize the system cpucaps, > the test for ARM64_HAS_ECV will always be false for CPUs present at boot > time, and will only be taken into account for CPUs onlined late > (including those which are hotplugged out and in again). > > Due to this, CPUs present and boot time may not use the intended divider > and scale factor to generate the event stream, and may differ from other > CPUs. > > Correct this by only initializing the event stream after cpucaps have been > finalized, registering a separate CPU hotplug callback for the event stream > configuration. Since the caps must be finalized by this point, use > cpus_have_final_cap() to verify this. Isn't this the same as 20230907133410.3817800-1-mark.rutland@arm.com? M.
On Thu, Sep 21, 2023 at 08:41:52AM +0100, Marc Zyngier wrote: > On Tue, 19 Sep 2023 10:28:14 +0100, > Mark Rutland <mark.rutland@arm.com> wrote: > > > > We attempt to initialize each CPU's arch_timer event stream in > > arch_timer_evtstrm_enable(), which we call from the > > arch_timer_starting_cpu() cpu hotplug callback which is registered early > > in boot. As this is registered before we initialize the system cpucaps, > > the test for ARM64_HAS_ECV will always be false for CPUs present at boot > > time, and will only be taken into account for CPUs onlined late > > (including those which are hotplugged out and in again). > > > > Due to this, CPUs present and boot time may not use the intended divider > > and scale factor to generate the event stream, and may differ from other > > CPUs. > > > > Correct this by only initializing the event stream after cpucaps have been > > finalized, registering a separate CPU hotplug callback for the event stream > > configuration. Since the caps must be finalized by this point, use > > cpus_have_final_cap() to verify this. > > Isn't this the same as 20230907133410.3817800-1-mark.rutland@arm.com? Yes; sorry -- I had to pull it into this series to avoid a conflict, and I had meant to note that in the cover and add the acks from you and Thomas here. I've folded those in now. Mark.
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index 7dd2c615bce23..d1e9e556da81a 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -917,7 +917,7 @@ static void arch_timer_evtstrm_enable(unsigned int divider) #ifdef CONFIG_ARM64 /* ECV is likely to require a large divider. Use the EVNTIS flag. */ - if (cpus_have_const_cap(ARM64_HAS_ECV) && divider > 15) { + if (cpus_have_final_cap(ARM64_HAS_ECV) && divider > 15) { cntkctl |= ARCH_TIMER_EVT_INTERVAL_SCALE; divider -= 8; } @@ -955,6 +955,30 @@ static void arch_timer_configure_evtstream(void) arch_timer_evtstrm_enable(max(0, lsb)); } +static int arch_timer_evtstrm_starting_cpu(unsigned int cpu) +{ + arch_timer_configure_evtstream(); + return 0; +} + +static int arch_timer_evtstrm_dying_cpu(unsigned int cpu) +{ + cpumask_clear_cpu(smp_processor_id(), &evtstrm_available); + return 0; +} + +static int __init arch_timer_evtstrm_register(void) +{ + if (!arch_timer_evt || !evtstrm_enable) + return 0; + + return cpuhp_setup_state(CPUHP_AP_ARM_ARCH_TIMER_EVTSTRM_STARTING, + "clockevents/arm/arch_timer_evtstrm:starting", + arch_timer_evtstrm_starting_cpu, + arch_timer_evtstrm_dying_cpu); +} +core_initcall(arch_timer_evtstrm_register); + static void arch_counter_set_user_access(void) { u32 cntkctl = arch_timer_get_cntkctl(); @@ -1016,8 +1040,6 @@ static int arch_timer_starting_cpu(unsigned int cpu) } arch_counter_set_user_access(); - if (evtstrm_enable) - arch_timer_configure_evtstream(); return 0; } @@ -1164,8 +1186,6 @@ static int arch_timer_dying_cpu(unsigned int cpu) { struct clock_event_device *clk = this_cpu_ptr(arch_timer_evt); - cpumask_clear_cpu(smp_processor_id(), &evtstrm_available); - arch_timer_stop(clk); return 0; } @@ -1279,6 +1299,7 @@ static int __init arch_timer_register(void) out_free: free_percpu(arch_timer_evt); + arch_timer_evt = NULL; out: return err; } diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 06dda85f04244..6008c308d7642 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -173,6 +173,7 @@ enum cpuhp_state { CPUHP_AP_ARM_L2X0_STARTING, CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING, CPUHP_AP_ARM_ARCH_TIMER_STARTING, + CPUHP_AP_ARM_ARCH_TIMER_EVTSTRM_STARTING, CPUHP_AP_ARM_GLOBAL_TIMER_STARTING, CPUHP_AP_JCORE_TIMER_STARTING, CPUHP_AP_ARM_TWD_STARTING,
We attempt to initialize each CPU's arch_timer event stream in arch_timer_evtstrm_enable(), which we call from the arch_timer_starting_cpu() cpu hotplug callback which is registered early in boot. As this is registered before we initialize the system cpucaps, the test for ARM64_HAS_ECV will always be false for CPUs present at boot time, and will only be taken into account for CPUs onlined late (including those which are hotplugged out and in again). Due to this, CPUs present and boot time may not use the intended divider and scale factor to generate the event stream, and may differ from other CPUs. Correct this by only initializing the event stream after cpucaps have been finalized, registering a separate CPU hotplug callback for the event stream configuration. Since the caps must be finalized by this point, use cpus_have_final_cap() to verify this. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Marc Zyngier <maz@kernel.org> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> --- drivers/clocksource/arm_arch_timer.c | 31 +++++++++++++++++++++++----- include/linux/cpuhotplug.h | 1 + 2 files changed, 27 insertions(+), 5 deletions(-)