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Message-Id: <20260204-topic-ti-dm-clkevt-v6-16-v3-2-83e65d01f4ae@baylibre.com>
Date: Wed, 04 Feb 2026 11:45:49 +0100
From: "Markus Schneider-Pargmann (TI.com)" <msp@...libre.com>
To: Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>
Cc: Vishal Mahaveer <vishalm@...com>, Kevin Hilman <khilman@...libre.com>,
Dhruva Gole <d-gole@...com>, Sebin Francis <sebin.francis@...com>,
Kendall Willis <k-willis@...com>, Akashdeep Kaur <a-kaur@...com>,
linux-kernel@...r.kernel.org,
"Markus Schneider-Pargmann (TI.com)" <msp@...libre.com>
Subject: [PATCH v3 2/3] clocksource/drivers/timer-ti-dm: Add clocksource
support
Add support for using the TI Dual-Mode Timer as a clocksource. The
driver automatically picks the first timer that is marked as always-on
on with the "ti,timer-alwon" property to be the clocksource.
The timer can then be used for CPU independent time keeping.
Signed-off-by: Markus Schneider-Pargmann (TI.com) <msp@...libre.com>
---
drivers/clocksource/timer-ti-dm.c | 137 ++++++++++++++++++++++++++++++++++++++
1 file changed, 137 insertions(+)
diff --git a/drivers/clocksource/timer-ti-dm.c b/drivers/clocksource/timer-ti-dm.c
index 793e7cdcb1b16b58db3a81668e3c8144efc7baaf..75f38394e2598d76c41dd2b250c0c42f9f48bbe0 100644
--- a/drivers/clocksource/timer-ti-dm.c
+++ b/drivers/clocksource/timer-ti-dm.c
@@ -20,6 +20,7 @@
#include <linux/clk.h>
#include <linux/clk-provider.h>
+#include <linux/clocksource.h>
#include <linux/cpu_pm.h>
#include <linux/module.h>
#include <linux/io.h>
@@ -27,8 +28,10 @@
#include <linux/err.h>
#include <linux/pm_runtime.h>
#include <linux/of.h>
+#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/platform_data/dmtimer-omap.h>
+#include <linux/sched_clock.h>
#include <clocksource/timer-ti-dm.h>
#include <linux/delay.h>
@@ -148,6 +151,15 @@ static u32 omap_reserved_systimers;
static LIST_HEAD(omap_timer_list);
static DEFINE_SPINLOCK(dm_timer_lock);
+struct dmtimer_clocksource {
+ struct clocksource dev;
+ struct dmtimer *timer;
+ unsigned int loadval;
+};
+
+static resource_size_t omap_dm_timer_clocksource_base;
+static void __iomem *omap_dm_timer_sched_clock_counter;
+
enum {
REQUEST_ANY = 0,
REQUEST_BY_ID,
@@ -1185,6 +1197,117 @@ static const struct dev_pm_ops omap_dm_timer_pm_ops = {
static const struct of_device_id omap_timer_match[];
+static void omap_dm_timer_find_alwon(void)
+{
+ struct device_node *np;
+
+ for_each_matching_node(np, omap_timer_match) {
+ struct resource res;
+
+ if (!of_device_is_available(np))
+ continue;
+
+ if (!of_property_read_bool(np, "ti,timer-alwon"))
+ continue;
+
+ if (of_address_to_resource(np, 0, &res))
+ continue;
+
+ omap_dm_timer_clocksource_base = res.start;
+
+ of_node_put(np);
+ return;
+ }
+
+ omap_dm_timer_clocksource_base = RESOURCE_SIZE_MAX;
+}
+
+static struct dmtimer_clocksource *omap_dm_timer_to_clocksource(struct clocksource *cs)
+{
+ return container_of(cs, struct dmtimer_clocksource, dev);
+}
+
+static u64 omap_dm_timer_read_cycles(struct clocksource *cs)
+{
+ struct dmtimer_clocksource *clksrc = omap_dm_timer_to_clocksource(cs);
+ struct dmtimer *timer = clksrc->timer;
+
+ return (u64)__omap_dm_timer_read_counter(timer);
+}
+
+static u64 notrace omap_dm_timer_read_sched_clock(void)
+{
+ /* Posted mode is not active here, so we can read directly */
+ return readl_relaxed(omap_dm_timer_sched_clock_counter);
+}
+
+static void omap_dm_timer_clocksource_suspend(struct clocksource *cs)
+{
+ struct dmtimer_clocksource *clksrc = omap_dm_timer_to_clocksource(cs);
+ struct dmtimer *timer = clksrc->timer;
+
+ clksrc->loadval = __omap_dm_timer_read_counter(timer);
+ __omap_dm_timer_stop(timer);
+}
+
+static void omap_dm_timer_clocksource_resume(struct clocksource *cs)
+{
+ struct dmtimer_clocksource *clksrc = omap_dm_timer_to_clocksource(cs);
+ struct dmtimer *timer = clksrc->timer;
+
+ dmtimer_write(timer, OMAP_TIMER_COUNTER_REG, clksrc->loadval);
+ dmtimer_write(timer, OMAP_TIMER_CTRL_REG, OMAP_TIMER_CTRL_ST | OMAP_TIMER_CTRL_AR);
+}
+
+static void omap_dm_timer_clocksource_unregister(void *data)
+{
+ struct clocksource *cs = data;
+
+ clocksource_unregister(cs);
+}
+
+static int omap_dm_timer_setup_clocksource(struct dmtimer *timer)
+{
+ struct device *dev = &timer->pdev->dev;
+ struct dmtimer_clocksource *clksrc;
+ int err;
+
+ __omap_dm_timer_init_regs(timer);
+
+ timer->reserved = 1;
+
+ clksrc = devm_kzalloc(dev, sizeof(*clksrc), GFP_KERNEL);
+ if (!clksrc)
+ return -ENOMEM;
+
+ clksrc->timer = timer;
+
+ clksrc->dev.name = "omap_dm_timer";
+ clksrc->dev.rating = 300;
+ clksrc->dev.read = omap_dm_timer_read_cycles;
+ clksrc->dev.mask = CLOCKSOURCE_MASK(32);
+ clksrc->dev.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+ clksrc->dev.suspend = omap_dm_timer_clocksource_suspend;
+ clksrc->dev.resume = omap_dm_timer_clocksource_resume;
+
+ dmtimer_write(timer, OMAP_TIMER_COUNTER_REG, 0);
+ dmtimer_write(timer, OMAP_TIMER_LOAD_REG, 0);
+ dmtimer_write(timer, OMAP_TIMER_CTRL_REG, OMAP_TIMER_CTRL_ST | OMAP_TIMER_CTRL_AR);
+
+ omap_dm_timer_sched_clock_counter = timer->func_base + _OMAP_TIMER_COUNTER_OFFSET;
+ sched_clock_register(omap_dm_timer_read_sched_clock, 32, timer->fclk_rate);
+
+ err = clocksource_register_hz(&clksrc->dev, timer->fclk_rate);
+ if (err)
+ return dev_err_probe(dev, err, "Could not register as clocksource\n");
+
+ err = devm_add_action_or_reset(dev, omap_dm_timer_clocksource_unregister, &clksrc->dev);
+ if (err)
+ return dev_err_probe(dev, err, "Could not register clocksource_unregister action\n");
+
+ return 0;
+}
+
/**
* omap_dm_timer_probe - probe function called for every registered device
* @pdev: pointer to current timer platform device
@@ -1198,8 +1321,12 @@ static int omap_dm_timer_probe(struct platform_device *pdev)
struct dmtimer *timer;
struct device *dev = &pdev->dev;
const struct dmtimer_platform_data *pdata;
+ struct resource *res;
int ret;
+ if (!omap_dm_timer_clocksource_base)
+ omap_dm_timer_find_alwon();
+
pdata = of_device_get_match_data(dev);
if (!pdata)
pdata = dev_get_platdata(dev);
@@ -1272,6 +1399,16 @@ static int omap_dm_timer_probe(struct platform_device *pdev)
timer->pdev = pdev;
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+ if (omap_dm_timer_clocksource_base && res &&
+ res->start == omap_dm_timer_clocksource_base &&
+ !IS_ERR_OR_NULL(timer->fclk)) {
+ ret = omap_dm_timer_setup_clocksource(timer);
+ if (ret)
+ return ret;
+ }
+
pm_runtime_enable(dev);
if (!timer->reserved) {
--
2.51.0
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