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

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Date:   Wed, 11 Oct 2023 12:06:20 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Mark Rutland <mark.rutland@....com>
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

On 11/10/2023 11:36, Mark Rutland wrote:
> 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.

Sure, thanks for letting me know. I was suspecting that was the case :)

I've dropped it

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