linux-kernel - Re: [PATCH v5 4/7] clocksource/drivers/exynos_mct: Use percpu interrupts only on ARM64

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Message-ID: <c09387b9-3fcc-4d0e-8e29-21dee196014a@samsung.com>
Date: Fri, 24 Oct 2025 13:19:03 +0200
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Will McVicker <willmcvicker@...gle.com>, Russell King
	<linux@...linux.org.uk>, Catalin Marinas <catalin.marinas@....com>, Will
	Deacon <will@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>, Thomas
	Gleixner <tglx@...utronix.de>, Krzysztof Kozlowski <krzk@...nel.org>, Alim
	Akhtar <alim.akhtar@...sung.com>, Ingo Molnar <mingo@...nel.org>, Peter
	Griffin <peter.griffin@...aro.org>, Youngmin Nam <youngmin.nam@...sung.com>
Cc: Donghoon Yu <hoony.yu@...sung.com>, Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>, John Stultz <jstultz@...gle.com>,
	Tudor Ambarus <tudor.ambarus@...aro.org>, André Draszik
	<andre.draszik@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
	linux-samsung-soc@...r.kernel.org, kernel-team@...roid.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v5 4/7] clocksource/drivers/exynos_mct: Use percpu
 interrupts only on ARM64

On 23.10.2025 22:52, Will McVicker wrote:
> From: Marek Szyprowski <m.szyprowski@...sung.com>
>
> For some unknown reasons forcing percpu interrupts for local timers
> breaks CPU hotplug for 'little' cores on legacy ARM 32bit Exynos based
> machines (for example Exynos5422-based Odroid-XU3/XU4 boards). Use percpu
> flag only when driver is compiled for newer ARM64 architecture.
>
> Fixes: f3cec54ee3bf ("clocksource/drivers/exynos_mct: Set local timer interrupts as percpu")

This tag doesn't make sense in this patchset. Simply squash this change 
with the previous one, adding the following tags:

Suggested-by: Marek Szyprowski <m.szyprowski@...sung.com>
Link: 
https://lore.kernel.org/all/20250827102645.1964659-1-m.szyprowski@samsung.com/ 

> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Reviewed-by: Peter Griffin <peter.griffin@...aro.org>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> ---
>   drivers/clocksource/exynos_mct.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
> index a5ef7d64b1c2..1429b9d03a58 100644
> --- a/drivers/clocksource/exynos_mct.c
> +++ b/drivers/clocksource/exynos_mct.c
> @@ -597,7 +597,8 @@ static int __init exynos4_timer_interrupts(struct device_node *np,
>   			if (request_irq(mct_irq,
>   					exynos4_mct_tick_isr,
>   					IRQF_TIMER | IRQF_NOBALANCING |
> -					IRQF_PERCPU,
> +					(IS_ENABLED(CONFIG_ARM64) ?
> +					 IRQF_PERCPU : 0),
>   					pcpu_mevt->name, pcpu_mevt)) {
>   				pr_err("exynos-mct: cannot register IRQ (cpu%d)\n",
>   									cpu);

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland