Re: [PATCH v4 5/6] clocksource/drivers/exynos_mct: Add module support

Hi Will,

sorry I missed to add you in Cc but the following proposal help in the 
module conversion:

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


On 25/06/2025 01:47, William McVicker wrote:

On 06/24/2025, Daniel Lezcano wrote:

quoted

On Fri, Jun 20, 2025 at 11:17:08AM -0700, 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>
[original commit from https://android.googlesource.com/kernel/gs/+/8a52a8288ec7d88ff78f0b37480dbb0e9c65bbfd]
Reviewed-by: Youngmin Nam <redacted>
Tested-by: Youngmin Nam <redacted>
Signed-off-by: Will McVicker <redacted>
---

...

quoted

-static int __init mct_init_spi(struct device_node *np)

__init_or_module

Thanks, I'll update in v5.

quoted

quoted

+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.

I took a second look at the TIMER_OF_DECLARE() macro and FWICT the timer will
only be enabled "very early" via timer_probe() if "MODULE" is not defined which
is only defined when this specific driver is compiled as a module. Note, this
"MODULE" define is not the same as the Kconfig option "CONFIG_MODULES".
That is why in my v1 and v2 patch [1] I had:

  #ifdef MODULE
    ...
    module_platform_driver(exynos4_mct_driver);
  #else
    TIMER_OF_DECLARE(...)
    TIMER_OF_DECLARE(...)
  #endif

However, I dropped that since Saravana mentioned that we should not be using
TIMER_OF_DECLARE() for drivers that can be modules. I don't have an ARM Exynos
device to verify dropping TIMER_OF_DECLARE() is safe. So if you and Saravana
agree, I can work on creating a patch to define TIMER_OF_DECLARE_MODULE() like
you proposed in [2] to handle this for all the drivers that are used for both ARM and
ARM64 SoCs.

Thanks,
Will

[1] https://lore.kernel.org/all/6e6b0f5f-ac60-48bb-af6c-fa58658d2639@linaro.org/ (local)
[2] https://lore.kernel.org/all/f2f914aa-c554-4135-afaa-f075537ed929@linaro.org/ (local)

<snip>

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