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Message-ID: <864jjrenxp.wl-maz@kernel.org>
Date: Mon, 18 Sep 2023 12:11:14 +0100
From: Marc Zyngier <maz@...nel.org>
To: Mark Rutland <mark.rutland@....com>
Cc: linux-arm-kernel@...ts.infradead.org, daniel.lezcano@...aro.org,
linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: Re: [PATCH] clocksource/drivers/arm_arch_timer: Initialize evtstrm after finalizing cpucaps
On Thu, 07 Sep 2023 14:34:10 +0100,
Mark Rutland <mark.rutland@....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
> 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>
Acked-by: Marc Zyngier <maz@...nel.org>
M.
--
Without deviation from the norm, progress is not possible.
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