[PATCH v2 0/7] Add module support for Arm64 Exynos MCT driver

[Youngmin Nam]

On Wed, Apr 02, 2025 at 04:33:51PM -0700, Will McVicker wrote:
> This series adds support to build the Arm64 Exynos MCT driver as a module. This
> is only possible on Arm64 SoCs since they can use the Arm architected timer as
> the clocksource. Once the Exynos MCT module is loaded and the device probes,
> the MCT is used as the wakeup source for the arch_timer to ensure the device
> can wakeup from the "c2" idle state.
> 
> These patches are originally from the downstream Pixel 6 (gs101) kernel found
> at [1] and have been adapted for upstream. Not only has the Exynos MCT driver
> been shipping as a module in the field with Android, but I've also tested this
> seris with the upstream kernel on my Pixel 6 Pro.
> 
> Thanks,
> Will
> 
> Note1, instructions to build and flash a Pixel 6 device with the upstream kernel
> can be found at [2].
> 
> Note2, this series is based off of linux-next/master commit 405e2241def8 ("Add
> linux-next specific files for 20250331").
> 
> [1] https://android.googlesource.com/kernel/gs/+log/refs/heads/android-gs-raviole-5.10-android12-d1
> [2] https://protect2.fireeye.com/v1/url?k=d287bb1b-b30cae21-d2863054-74fe4860008a-f0cb7ae29f3b1b85&q=1&e=4e8467a4-13da-4dd4-a8fd-4ddfc38e89b4&u=https%3A%2F%2Fgit.codelinaro.org%2Flinaro%2Fgooglelt%2Fpixelscripts%2F-%2Fblob%2Fclo%2Fmain%2FREADME.md%3Fref_type%3Dheads
> 
> Cc: Alim Akhtar <alim.akhtar at samsung.com>
> Cc: Daniel Lezcano <daniel.lezcano at linaro.org>
> Cc: Donghoon Yu <hoony.yu at samsung.com>
> Cc: Hosung Kim <hosung0.kim at samsung.com>
> Cc: kernel-team at android.com
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: linux-kernel at vger.kernel.org
> Cc: Rob Herring <robh at kernel.org>
> Cc: Saravana Kannan <saravanak at google.com>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Youngmin Nam <youngmin.nam at samsung.com>
> Cc: Peter Griffin <peter.griffin at linaro.org>
> Cc: Tudor Ambarus <tudor.ambarus at linaro.org>
> Cc: André Draszik <andre.draszik at linaro.org>
> Cc: Will Deacon <will at kernel.org>
> Cc: Conor Dooley <conor+dt at kernel.org>
> Cc: Krzysztof Kozlowski <krzk at kernel.org>
> Cc: linux-samsung-soc at vger.kernel.org
> 
> ---
> Changes in v2:
> - Re-worked patch v1 5 based on Rob Herring's review to use the compatible data
>   for retrieving the mct_init function pointer.
> - Updated the Kconfig logic to disallow building the Exynos MCT driver as
>   a module for ARM32 configurations based on Krzysztof Kozlowski's findings.
> - Added comments and clarified commit messages in patches 1 and 2 based on
>   reviews from John Stultz and Youngmin Nam.
> - Fixed an issue found during testing that resulted in the device getting
>   stuck on boot. This is included in v2 as patch 5.
> - Collected *-by tags
> - Rebased to the latest linux-next/master.
> 
> ---
> Donghoon Yu (1):
>   clocksource/drivers/exynos_mct: Add module support
> 
> Hosung Kim (1):
>   clocksource/drivers/exynos_mct: Set local timer interrupts as percpu
> 
> Will Deacon (1):
>   arm64: dts: exynos: gs101: Add 'local-timer-stop' to cpuidle nodes
> 
> Will McVicker (4):
>   of/irq: Export of_irq_count for modules
>   clocksource/drivers/exynos_mct: Don't register as a sched_clock on
>     arm64
>   clocksource/drivers/exynos_mct: Fix uninitialized irq name warning
>   arm64: exynos: Drop select CLKSRC_EXYNOS_MCT
> 
>  arch/arm64/Kconfig.platforms                 |  1 -
>  arch/arm64/boot/dts/exynos/google/gs101.dtsi |  3 +
>  drivers/clocksource/Kconfig                  |  3 +-
>  drivers/clocksource/exynos_mct.c             | 73 ++++++++++++++++----
>  drivers/of/irq.c                             |  1 +
>  5 files changed, 67 insertions(+), 14 deletions(-)
> 
> -- 
> 2.49.0.472.ge94155a9ec-goog
> 
> 

Hi Will.

I tested this series on a E850-96(Exynos3830 based) board and it's working as a moudle.

# dmesg | grep mct
[7.376224] clocksource: mct-frc: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 73510017198 ns

# lsmod | grep exynos_mct
exynos_mct             12288  0

# cat /sys/devices/system/clocksource/clocksource0/current_clocksource
arch_sys_counter
# cat /sys/devices/system/clockevents/clockevent0/current_device
arch_sys_timer

# cat /proc/interrupts 
        CPU0    CPU1    CPU2    CPU3    CPU4    CPU5    CPU6    CPU7
 12:    2566    2752    2467    4026    3372    2822    2115    3227 GIC-0  27 Level     arch_timer
...
 77:       0       0       0       0       0       0       0       0 GIC-0 235 Level     mct_comp_irq
 78:       0       0       0       0       0       0       0       0 GIC-0 239 Level     mct_tick0
 79:       0       0       0       0       0       0       0       0 GIC-0 240 Level     mct_tick1
 80:       0       0       0       0       0       0       0       0 GIC-0 241 Level     mct_tick2
 81:       0       0       0       0       0       0       0       0 GIC-0 242 Level     mct_tick3
 82:       0       0       0       0       0       0       0       0 GIC-0 243 Level     mct_tick4
 83:       0       0       0       0       0       0       0       0 GIC-0 244 Level     mct_tick5
 84:       0       0       0       0       0       0       0       0 GIC-0 245 Level     mct_tick6
 85:       0       0       0       0       0       0       0       0 GIC-0 246 Level     mct_tick7

Reviewed-by: Youngmin Nam <youngmin.nam at samsung.com>
Tested-by: Youngmin Nam <youngmin.nam at samsung.com>

Thanks,
Youngmin