linux-kernel - [PATCH v2 0/4] clocksource: Add standalone MMIO ARM arch timer driver

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Message-Id: <20250814154622.10193-1-maz@kernel.org>
Date: Thu, 14 Aug 2025 16:46:18 +0100
From: Marc Zyngier <maz@...nel.org>
To: linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Sudeep Holla <sudeep.holla@....com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mark Rutland <mark.rutland@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	Steven Price <steven.price@....com>
Subject: [PATCH v2 0/4] clocksource: Add standalone MMIO ARM arch timer driver

For the past 10 years, both Mark and I have been lamenting about the
sorry state of the badly named "arch_timer" driver, and about the way
the MMIO part is intricately weaved into the system-register part.

The time has finally come to take a stab at it.

This small series simply creates a new timer driver for the MMIO arch
timer, and only that. It is an actual driver, and not some kludge that
has to run super early (that's what the per-CPU timers are for). This
allows, in turn, a pretty large cleanup of the per-CPU driver, though
there is more to come -- one thing at a time.

As an added bonus, we get a clocksource, which the original code
didn't provide. Just in case it might be useful. The end-result is far
more readable, and about 100 lines smaller.

Patches on top of 6.17-rc1.

* From v1 [1]:

  - Narrow the max delta to something that fits an unsigned long, as
    the core code doesn't deal with 64bit quantities on 32bit CPUs.

  - Collected RBs and TBs from Sudeep, with thanks.

Marc Zyngier (4):
  ACPI: GTDT: Generate platform devices for MMIO timers
  clocksource/drivers/arm_arch_timer: Add standalone MMIO driver
  clocksource/drivers/arm_arch_timer_mmio: Switch over to standalone
    driver
  clocksource/drivers/arm_arch_timer_mmio: Add MMIO clocksource

 MAINTAINERS                               |   1 +
 drivers/acpi/arm64/gtdt.c                 |  29 +-
 drivers/clocksource/Makefile              |   1 +
 drivers/clocksource/arm_arch_timer.c      | 686 ++--------------------
 drivers/clocksource/arm_arch_timer_mmio.c | 440 ++++++++++++++
 include/clocksource/arm_arch_timer.h      |   5 -
 6 files changed, 532 insertions(+), 630 deletions(-)
 create mode 100644 drivers/clocksource/arm_arch_timer_mmio.c

-- 
2.39.2