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Message-ID: <40d3f3c9-7526-440b-9dbd-7ead22c8562a@samsung.com>
Date: Fri, 24 Oct 2025 13:14:02 +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
Subject: Re: [PATCH v5 6/7] clocksource/drivers/exynos_mct: Add module
support
On 23.10.2025 22:52, 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>
> Signed-off-by: Will McVicker <willmcvicker@...gle.com>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> [original commit from https://android.googlesource.com/kernel/gs/+/8a52a8288ec7d88ff78f0b37480dbb0e9c65bbfd]
> Reviewed-by: Youngmin Nam <youngmin.nam@...sung.com> # AOSP -> Linux port
> Tested-by: Youngmin Nam <youngmin.nam@...sung.com> # AOSP -> Linux port
> ---
> drivers/clocksource/Kconfig | 3 +-
> drivers/clocksource/exynos_mct.c | 56 +++++++++++++++++++++++++++-----
> 2 files changed, 49 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index ffcd23668763..9450cfaf982f 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -451,7 +451,8 @@ config ATMEL_TCB_CLKSRC
> Support for Timer Counter Blocks on Atmel SoCs.
>
> config CLKSRC_EXYNOS_MCT
> - bool "Exynos multi core timer driver" if COMPILE_TEST
> + tristate "Exynos multi core timer driver" if ARM64
> + default y if ARCH_EXYNOS || COMPILE_TEST
> depends on ARM || ARM64
> depends on ARCH_ARTPEC || ARCH_EXYNOS || COMPILE_TEST
> help
> diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
> index fece6bbc190e..a87caf3928ef 100644
> --- a/drivers/clocksource/exynos_mct.c
> +++ b/drivers/clocksource/exynos_mct.c
> @@ -15,9 +15,11 @@
> #include <linux/cpu.h>
> #include <linux/delay.h>
> #include <linux/percpu.h>
> +#include <linux/module.h>
> #include <linux/of.h>
> #include <linux/of_irq.h>
> #include <linux/of_address.h>
> +#include <linux/platform_device.h>
> #include <linux/clocksource.h>
> #include <linux/sched_clock.h>
>
> @@ -217,6 +219,7 @@ static struct clocksource mct_frc = {
> .mask = CLOCKSOURCE_MASK(32),
> .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> .resume = exynos4_frc_resume,
> + .owner = THIS_MODULE,
> };
>
> /*
> @@ -241,7 +244,7 @@ static cycles_t exynos4_read_current_timer(void)
> }
> #endif
>
> -static int __init exynos4_clocksource_init(bool frc_shared)
> +static int exynos4_clocksource_init(bool frc_shared)
> {
> /*
> * When the frc is shared, the main processor should have already
> @@ -336,6 +339,7 @@ static struct clock_event_device mct_comp_device = {
> .set_state_oneshot = mct_set_state_shutdown,
> .set_state_oneshot_stopped = mct_set_state_shutdown,
> .tick_resume = mct_set_state_shutdown,
> + .owner = THIS_MODULE,
> };
>
> static irqreturn_t exynos4_mct_comp_isr(int irq, void *dev_id)
> @@ -476,6 +480,7 @@ static int exynos4_mct_starting_cpu(unsigned int cpu)
> evt->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
> CLOCK_EVT_FEAT_PERCPU;
> evt->rating = MCT_CLKEVENTS_RATING;
> + evt->owner = THIS_MODULE;
>
> exynos4_mct_write(TICK_BASE_CNT, mevt->base + MCT_L_TCNTB_OFFSET);
>
> @@ -511,7 +516,7 @@ static int exynos4_mct_dying_cpu(unsigned int cpu)
> return 0;
> }
>
> -static int __init exynos4_timer_resources(struct device_node *np)
> +static int exynos4_timer_resources(struct device_node *np)
> {
> struct clk *mct_clk, *tick_clk;
>
> @@ -539,7 +544,7 @@ static int __init exynos4_timer_resources(struct device_node *np)
> * @local_idx: array mapping CPU numbers to local timer indices
> * @nr_local: size of @local_idx array
> */
> -static int __init exynos4_timer_interrupts(struct device_node *np,
> +static int exynos4_timer_interrupts(struct device_node *np,
> unsigned int int_type,
> const u32 *local_idx,
> size_t nr_local)
> @@ -653,7 +658,7 @@ static int __init exynos4_timer_interrupts(struct device_node *np,
> return err;
> }
>
> -static int __init mct_init_dt(struct device_node *np, unsigned int int_type)
> +static int mct_init_dt(struct device_node *np, unsigned int int_type)
> {
> bool frc_shared = of_property_read_bool(np, "samsung,frc-shared");
> u32 local_idx[MCT_NR_LOCAL] = {0};
> @@ -701,15 +706,48 @@ static int __init mct_init_dt(struct device_node *np, unsigned int int_type)
> return exynos4_clockevent_init();
> }
>
> -
> -static int __init mct_init_spi(struct device_node *np)
> +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);
> +
> +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,
> + },
> +};
> +
> +static __init int exynos_mct_init(void)
> +{
> + return platform_driver_register(&exynos4_mct_driver);
> +}
> +module_init(exynos_mct_init);
> +
> +MODULE_DESCRIPTION("Exynos Multi Core Timer Driver");
> +MODULE_LICENSE("GPL");
Sorry, but this still won't work on legacy ARM 32bit systems with MCT as
the only clocksource, which needs a driver available very early (that's
why it used TIMER_OF_DECLAREmacro). You need to make it conditional
under CONFIG_ARM:
#ifdef CONFIG_ARM
TIMER_OF_DECLARE(exynos4210, "samsung,exynos4210-mct", mct_init_spi);
TIMER_OF_DECLARE(exynos4412, "samsung,exynos4412-mct", mct_init_ppi);
#else
... (module-based intialization).
#endif
The latter case might skip the legacy exynos4412-style case, as all MCT
variants used on ARM 64bit systems are exynos4210 compatible.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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