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

[Daniel Lezcano]

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@xxxxxxxxxx/


On 25/06/2025 01:47, William McVicker wrote:
> On 06/24/2025, Daniel Lezcano wrote:
> > On Fri, Jun 20, 2025 at 11:17:08AM -0700, Will McVicker wrote:
> > > From: Donghoon Yu <hoony.yu@xxxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxxx>
> > > Signed-off-by: Youngmin Nam <youngmin.nam@xxxxxxxxxxx>
> > > [original commit from https://android.googlesource.com/kernel/gs/+/8a52a8288ec7d88ff78f0b37480dbb0e9c65bbfd]
> > > Reviewed-by: Youngmin Nam <youngmin.nam@xxxxxxxxxxx>
> > > Tested-by: Youngmin Nam <youngmin.nam@xxxxxxxxxxx>
> > > Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx>
> > > ---
> >
> > ...
> >
> > > -static int __init mct_init_spi(struct device_node *np)
> >
> > __init_or_module
>
> Thanks, I'll update in v5.
>
> > > +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@xxxxxxxxxx/
> [2] https://lore.kernel.org/all/f2f914aa-c554-4135-afaa-f075537ed929@xxxxxxxxxx/
>
> <snip>


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