linux-kernel - [PATCH 4/4] clocksource/drivers/arm_arch_timer

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Message-Id: <20250807160243.1970533-5-maz@kernel.org>
Date: Thu,  7 Aug 2025 17:02:43 +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>
Subject: [PATCH 4/4] clocksource/drivers/arm_arch_timer_mmio: Add MMIO clocksource

The MMIO driver can also double as a clocksource, something that was
missing in its previous incarnation. Add it for completeness.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 drivers/clocksource/arm_arch_timer_mmio.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/clocksource/arm_arch_timer_mmio.c b/drivers/clocksource/arm_arch_timer_mmio.c
index fa7294ab609ce..f88e960c24006 100644
--- a/drivers/clocksource/arm_arch_timer_mmio.c
+++ b/drivers/clocksource/arm_arch_timer_mmio.c
@@ -45,6 +45,7 @@ enum arch_timer_access {
 
 struct arch_timer {
 	struct clock_event_device	evt;
+	struct clocksource		cs;
 	struct arch_timer_mem		*gt_block;
 	void __iomem			*base;
 	enum arch_timer_access		access;
@@ -52,6 +53,7 @@ struct arch_timer {
 };
 
 #define evt_to_arch_timer(e) container_of(e, struct arch_timer, evt)
+#define cs_to_arch_timer(c) container_of(c, struct arch_timer, cs)
 
 static void arch_timer_mmio_write(struct arch_timer *timer,
 				  enum arch_timer_reg reg, u64 val)
@@ -128,6 +130,13 @@ static noinstr u64 arch_counter_mmio_get_cnt(struct arch_timer *t)
 	return ((u64) cnt_hi << 32) | cnt_lo;
 }
 
+static u64 arch_mmio_counter_read(struct clocksource *cs)
+{
+	struct arch_timer *at = cs_to_arch_timer(cs);
+
+	return arch_counter_mmio_get_cnt(at);
+}
+
 static int arch_timer_mmio_shutdown(struct clock_event_device *clk)
 {
 	struct arch_timer *at = evt_to_arch_timer(clk);
@@ -255,6 +264,16 @@ static void arch_timer_mmio_setup(struct arch_timer *at, int irq)
 	clockevents_config_and_register(&at->evt, at->rate, 0xf, CLOCKSOURCE_MASK(56));
 
 	enable_irq(at->evt.irq);
+
+	at->cs = (struct clocksource) {
+		.name	= "arch_mmio_counter",
+		.rating	= 300,
+		.read	= arch_mmio_counter_read,
+		.mask	= CLOCKSOURCE_MASK(56),
+		.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	};
+
+	clocksource_register_hz(&at->cs, at->rate);
 }
 
 static int arch_timer_mmio_frame_register(struct platform_device *pdev,
-- 
2.39.2