Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:4 as permitted sender) client-ip=2620:137:e000::3:4;
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Mark Rutland <mark.rutland@arm.com>,
        linux-arm-kernel@lists.infradead.org
Cc:     daniel.lezcano@linaro.org, linux-kernel@vger.kernel.org,
        mark.rutland@arm.com, maz@kernel.org
Subject: Re: [PATCH] clocksource/drivers/arm_arch_timer: Initialize evtstrm
 after finalizing cpucaps
In-Reply-To: <20230907133410.3817800-1-mark.rutland@arm.com>
References: <20230907133410.3817800-1-mark.rutland@arm.com>
Date:   Fri, 15 Sep 2023 21:14:25 +0200
Message-ID: <87y1h7z1ta.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Thu, Sep 07 2023 at 14:34, 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@arm.com>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>

Acked-by: Thomas Gleixner <tglx@linutronix.de>