linux-kernel - Re: [PATCH] clocksource/drivers/arm_arch_timer: Initialize evtstrm after finalizing cpucaps

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Message-ID: <ZSZsogqIgG863ucA@FVFF77S0Q05N>
Date:   Wed, 11 Oct 2023 10:36:34 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        maz@...nel.org, tglx@...utronix.de
Subject: Re: [PATCH] clocksource/drivers/arm_arch_timer: Initialize evtstrm
 after finalizing cpucaps

Hi Daniel,

On Wed, Oct 11, 2023 at 10:30:39AM +0200, Daniel Lezcano wrote:
> On 07/09/2023 15:34, Mark Rutland 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
> > spus_have_final_cap() to verify this.
> > 
> > Signed-off-by: Mark Rutland <mark.rutland@....com>
> > Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> > Cc: Marc Zyngier <maz@...nel.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > ---
> 
> Applied thanks

This got folded into a larger series that we were hoping to take through the arm64 tree:

  https://lore.kernel.org/linux-arm-kernel/20231010103139.3113421-1-mark.rutland@arm.com/
  https://lore.kernel.org/linux-arm-kernel/20231010103139.3113421-2-mark.rutland@arm.com/

I think that won't conflict, since all that's changed is the commit text, but
it might be worth dropping this patch for now to avoid the risk of a conflict.

Thanks,
Mark.