Re: [PATCH v5 6/7] clocksource/drivers/exynos_mct: Add module support

On 10/24/2025, Marek Szyprowski wrote:

On 23.10.2025 22:52, Will McVicker wrote:

quoted

From: Donghoon Yu <redacted>

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 <redacted>
Signed-off-by: Youngmin Nam <redacted>
Signed-off-by: Will McVicker <redacted>
Signed-off-by: Daniel Lezcano <redacted>
[original commit from https://android.googlesource.com/kernel/gs/+/8a52a8288ec7d88ff78f0b37480dbb0e9c65bbfd]
Reviewed-by: Youngmin Nam <redacted> # AOSP -> Linux port
Tested-by: Youngmin Nam <redacted> # 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:

Can we rely on the bootloader to setup the MCT timer and then hand-off at boot
once the driver is initialized?

Daniel was working on a solution to transparently handle calling
TIMER_OF_DECLARE() when a timer driver can be configured as both a module or
built-in here:

  https://lore.kernel.org/all/20250625085715.889837-1-daniel.lezcano@linaro.org/ (local)

Daniel, do you have plans to finish that? In the meantime, can we go with the
`#if CONFIG_ARM` solution?

Thanks,
Will

<snip>