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Message-ID: <691f464e-1c91-4752-8218-74b9ebf49018@samsung.com>
Date: Fri, 21 Nov 2025 13:16:43 +0100
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>
Cc: Donghoon Yu <hoony.yu@...sung.com>, Rob Herring <robh@...nel.org>, John
Stultz <jstultz@...gle.com>, Youngmin Nam <youngmin.nam@...sung.com>, Peter
Griffin <peter.griffin@...aro.org>, 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 v6 0/6] Add module support for Arm64 Exynos MCT driver
On 20.11.2025 19:42, 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 series with the upstream kernel on my Pixel 6 Pro.
>
> To verify the module on Pixel 6 Pro is used and the arch_timer is used as the
> main clocksource, I ran these tests:
>
> # lsmod | grep exynos_mct
> exynos_mct 24576 9 [permanent]
>
> $ cat /proc/interrupts | grep -E "mct|arch_timer"
> 23: 222 171 211 139 184 124 825 378 GICv3 30 Level arch_timer
> 117: 1 0 0 0 0 0 0 0 GICv3 785 Level mct_comp_irq
> 118: 228 0 0 0 0 0 0 0 GICv3 789 Level mct_tick0
> 119: 0 351 0 0 0 0 0 0 GICv3 790 Level mct_tick1
> 120: 0 0 1490 0 0 0 0 0 GICv3 791 Level mct_tick2
> 121: 0 0 0 325 0 0 0 0 GICv3 792 Level mct_tick3
> 122: 0 0 0 0 97 0 0 0 GICv3 793 Level mct_tick4
> 123: 0 0 0 0 0 150 0 0 GICv3 794 Level mct_tick5
> 124: 0 0 0 0 0 0 188 0 GICv3 795 Level mct_tick6
> 125: 0 0 0 0 0 0 0 157 GICv3 796 Level mct_tick7
>
> # cat /sys/devices/system/clocksource/clocksource0/current_clocksource
> arch_sys_counter
>
> I also compile tested for ARCH=ARM DEFCONFIG=multi_v7_defconfig with the
> following debug configs to ensure the section mismatches are fixed:
> CONFIG_DEBUG_SECTION_MISMATCH=y
> # CONFIG_SECTION_MISMATCH_WARN_ONLY is not set
>
> Any additional testing is much appreciated!
Works fine on 32bit Exynos systems in my test farm!
Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> 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 krzk/for-next commit 870f6ca955ea ("Merge
> branch 'next/clk' into for-next").
>
> [1] https://android.googlesource.com/kernel/gs/+log/refs/heads/android-gs-raviole-5.10-android12-d1
> [2] https://gitlab.com/LinaroLtd/googlelt/pixelscripts/-/blob/clo/main/README.md?ref_type=heads
>
> Cc: Alim Akhtar <alim.akhtar@...sung.com>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Cc: Donghoon Yu <hoony.yu@...sung.com>
> Cc: Hosung Kim <hosung0.kim@...sung.com>
> Cc: Rob Herring <robh@...nel.org>
> Cc: John Stultz <jstultz@...gle.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Youngmin Nam <youngmin.nam@...sung.com>
> Cc: Peter Griffin <peter.griffin@...aro.org>
> Cc: Tudor Ambarus <tudor.ambarus@...aro.org>
> Cc: André Draszik <andre.draszik@...aro.org>
> Cc: Will Deacon <will@...nel.org>
> Cc: Conor Dooley <conor+dt@...nel.org>
> Cc: Krzysztof Kozlowski <krzk@...nel.org>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: linux-samsung-soc@...r.kernel.org
> Cc: kernel-team@...roid.com
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> ---
>
> Changes in v6:
> - Updated module support to only register the MCT driver as a platform driver
> for ARM64 to ensure ARM 32-bit SoCs continue to probe the MCT driver very
> early.
> - Squashed the percpu fix suggested by Marek Szyprowski in
> https://lore.kernel.org/all/20250827102645.1964659-1-m.szyprowski@samsung.com/
> together with patch 3/6.
>
> Changes in v5:
> - Fixed section mismatch issues.
> - Addressed Arnd's concerns regarding potential issues with unloading and/or
> unbinding the driver.
> - Fixed SoB concerns to clarify the development chain from AOSP to Linux.
> - Pulled in https://lore.kernel.org/all/20250827102645.1964659-1-m.szyprowski@samsung.com/
> to limit percpu interrupts only for ARM64.
>
> Changes in v4:
> - Missed the "v3" string in the previous series for the actual patches
> - Re-generated patches with --base a15edf91668beefdb5171c53fa698c9b43dd1e0d
> for kernel test robot.
>
> Changes in v3:
> - Rebased on top of Daniel's timer modularization prep series [3] and
> krzk/for-next commit a15edf91668b ("Merge branch 'next/dt64' into
> for-next")
> - Added owner references to Exynos MCT clocksource and clockevent objects.
> - Dropped #ifdef MODULE conditional section in favor of just using
> module_platform_driver() which will properly handle setting up the
> of_device_id table based on if the driver is built-in or a module.
> - Update commit message for patch 2 based on John's feedback.
> - Dropped DT change from v2 as it was picked up by Krzysztof for CPU Idle.
>
> 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 (2):
> clocksource/drivers/exynos_mct: Don't register as a sched_clock on
> arm64
> clocksource/drivers/exynos_mct: Add module support for ARM64
>
> Hosung Kim (1):
> clocksource/drivers/exynos_mct: Set percpu local timer interrupts for
> ARM64
>
> Will McVicker (3):
> ARM: make register_current_timer_delay() accessible after init
> clocksource/drivers/exynos_mct: Fix uninitialized irq name warning
> arm64: exynos: Drop select CLKSRC_EXYNOS_MCT
>
> arch/arm/lib/delay.c | 2 +-
> arch/arm64/Kconfig.platforms | 1 -
> drivers/clocksource/Kconfig | 3 +-
> drivers/clocksource/exynos_mct.c | 87 +++++++++++++++++++++++++++-----
> 4 files changed, 78 insertions(+), 15 deletions(-)
>
>
> base-commit: 870f6ca955ea3f23b4d7824c815c81180a6d7c48
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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