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Message-ID: <20251023205041.2027336-1-willmcvicker@google.com>
Date: Thu, 23 Oct 2025 20:50:26 +0000
From: Will McVicker <willmcvicker@...gle.com>
To: 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>, Peter Griffin <peter.griffin@...aro.org>,
Ingo Molnar <mingo@...nel.org>, Youngmin Nam <youngmin.nam@...sung.com>,
Will McVicker <willmcvicker@...gle.com>, Hosung Kim <hosung0.kim@...sung.com>
Cc: Donghoon Yu <hoony.yu@...sung.com>, Rob Herring <robh@...nel.org>,
Saravana Kannan <saravanak@...gle.com>, John Stultz <jstultz@...gle.com>,
Tudor Ambarus <tudor.ambarus@...aro.org>,
"André Draszik" <andre.draszik@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
Marek Szyprowski <m.szyprowski@...sung.com>, linux-samsung-soc@...r.kernel.org,
kernel-team@...roid.com, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v5 0/7] Add module support for Arm64 Exynos MCT driver
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 20480 9 [permanent]
# cat /proc/interrupts | grep -E "mct|arch_timer"
23: 759 1009 741 477 601 405 1350 789 GICv3 30 Level arch_timer
117: 1 0 0 0 0 0 0 0 GICv3 785 Level mct_comp_irq
118: 2126 0 0 0 0 0 0 0 GICv3 789 Level mct_tick0
119: 0 1442 0 0 0 0 0 0 GICv3 790 Level mct_tick1
120: 0 0 4617 0 0 0 0 0 GICv3 791 Level mct_tick2
121: 0 0 0 2617 0 0 0 0 GICv3 792 Level mct_tick3
122: 0 0 0 0 4173 0 0 0 GICv3 793 Level mct_tick4
123: 0 0 0 0 0 2217 0 0 GICv3 794 Level mct_tick5
124: 0 0 0 0 0 0 1618 0 GICv3 795 Level mct_tick6
125: 0 0 0 0 0 0 0 894 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!
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 73f7017e6636 ("Merge
branch 'fixes' into for-next").
[1] https://android.googlesource.com/kernel/gs/+log/refs/heads/android-gs-raviole-5.10-android12-d1
[2] https://git.codelinaro.org/linaro/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: Saravana Kannan <saravanak@...gle.com>
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 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
Hosung Kim (1):
clocksource/drivers/exynos_mct: Set local timer interrupts as percpu
Marek Szyprowski (1):
clocksource/drivers/exynos_mct: Use percpu interrupts only on 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 | 81 ++++++++++++++++++++++++++------
4 files changed, 70 insertions(+), 17 deletions(-)
base-commit: 73f7017e663620a616171cc80d62504a624dc4de
--
2.51.1.821.gb6fe4d2222-goog
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