linux-kernel - Re: [PATCH v4 5/6] clocksource/drivers/exynos

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Message-ID: <aFqsqr7i7cdR5-I0@mai.linaro.org>
Date: Tue, 24 Jun 2025 15:48:26 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Will McVicker <willmcvicker@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Krzysztof Kozlowski <krzk@...nel.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Donghoon Yu <hoony.yu@...sung.com>,
	Hosung Kim <hosung0.kim@...sung.com>, kernel-team@...roid.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	John Stultz <jstultz@...gle.com>,
	Youngmin Nam <youngmin.nam@...sung.com>,
	Peter Griffin <peter.griffin@...aro.org>,
	Tudor Ambarus <tudor.ambarus@...aro.org>,
	André Draszik <andre.draszik@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 5/6] clocksource/drivers/exynos_mct: Add module support

On Fri, Jun 20, 2025 at 11:17:08AM -0700, Will McVicker wrote:
> From: Donghoon Yu <hoony.yu@...sung.com>
> 
> On Arm64 platforms the Exynos MCT driver can be built as a module. On
> boot (and even after boot) the arch_timer is used as the clocksource and
> tick timer. Once the MCT driver is loaded, it can be used as the wakeup
> source for the arch_timer.
> 
> Signed-off-by: Donghoon Yu <hoony.yu@...sung.com>
> Signed-off-by: Youngmin Nam <youngmin.nam@...sung.com>
> [original commit from https://android.googlesource.com/kernel/gs/+/8a52a8288ec7d88ff78f0b37480dbb0e9c65bbfd]
> Reviewed-by: Youngmin Nam <youngmin.nam@...sung.com>
> Tested-by: Youngmin Nam <youngmin.nam@...sung.com>
> Signed-off-by: Will McVicker <willmcvicker@...gle.com>
> ---

...

> -static int __init mct_init_spi(struct device_node *np)

__init_or_module

> +static int mct_init_spi(struct device_node *np)
>  {
>  	return mct_init_dt(np, MCT_INT_SPI);
>  }
>  
> -static int __init mct_init_ppi(struct device_node *np)
> +static int mct_init_ppi(struct device_node *np)
>  {
>  	return mct_init_dt(np, MCT_INT_PPI);
>  }
> -TIMER_OF_DECLARE(exynos4210, "samsung,exynos4210-mct", mct_init_spi);
> -TIMER_OF_DECLARE(exynos4412, "samsung,exynos4412-mct", mct_init_ppi);

Are you sure this is not going to hurt the ARM platforms ? Here the
timer is enabled very early in the boot process while with this change
the timer will be available later.

> +static int exynos4_mct_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	int (*mct_init)(struct device_node *np);
> +
> +	mct_init = of_device_get_match_data(dev);
> +	if (!mct_init)
> +		return -EINVAL;
> +
> +	return mct_init(dev->of_node);
> +}
> +
> +static const struct of_device_id exynos4_mct_match_table[] = {
> +	{ .compatible = "samsung,exynos4210-mct", .data = &mct_init_spi, },
> +	{ .compatible = "samsung,exynos4412-mct", .data = &mct_init_ppi, },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, exynos4_mct_match_table);
> +
> +static struct platform_driver exynos4_mct_driver = {
> +	.probe		= exynos4_mct_probe,
> +	.driver		= {
> +		.name	= "exynos-mct",
> +		.of_match_table = exynos4_mct_match_table,
> +	},
> +};
> +module_platform_driver(exynos4_mct_driver);
> +
> +MODULE_DESCRIPTION("Exynos Multi Core Timer Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.50.0.rc2.761.g2dc52ea45b-goog
> 

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