[PATCH v4 0/2] Add Realtek System Timer

[PATCH v4 0/2] Add Realtek System Timer

[Hao-Wen Ting]

Changes v4:
PATCH 1/2
- Adjust compatible property description to match actual DTS and validate
  it with dt_binding_check.
- Refine binding documentation descriptions.

PATCH 2/2
- Reorder variable declarations.
- Remove debug prints.
- Eliminate unnecessary line breaks.
- Switch to set_next_event() callback instead of set_next_ktime().
- Remove operations that caused build error.
- Rename the struct `timer_of` instance variable for clarity.
- Tabularize struct initializers.
- Refine descriptions.
---

Changes v3:
PATCH 1/2
- Rename binding documentation to match compatible string.
- Drop redundant "binding" from commit subject.
- Add example node and description for realtek,rtd1635-systimer.

PATCH 2/2
- Add Kconfig dependency: ARCH_REALTEK || COMPILE_TEST.
---

Changes v2:
PATCH 1/2
- Add full name 'system timer' to description.
- Remove redundant commit messages.
- Clarify compatible strings for specific verified SoCs.
- Remove redundant reg and interrupts description sentences.
- Use generic node name in example.

PATCH 2/2
- Correct MAINTAINERS to alphabetical order.
- Update Kconfig: switch dependency to ARM/ARM64.
- Remove redundant pr_info output.
---

This patch series adds support for the Realtek System Timer, a 64-bit counter
that serves as a clock event device on Realtek SoCs.

Technical details:
- Implements a 64-bit timer operating at 1MHz fixed frequency.
- Supports oneshot mode and tick broadcast functionality.
- Remains active during CPU power-down states.

Testing:
- Functionality verified for tick broadcast on both RTD1625 and RTD1635 SoCs.
- Confirmed binding documentation passes yamllint, dt_binding_check, and dtbs_check.
- Driver successfully built under COMPILE_TEST.

Patch organization:
Patch 1/2: Device Tree binding documentation
Patch 2/2: Clocksource driver implementation

Best regards,
Hao-Wen Ting

Hao-Wen Ting (2):
  dt-bindings: timer: Add Realtek SYSTIMER
  clocksource: Add Realtek system timer driver

 .../timer/realtek,rtd1625-systimer.yaml       |  47 ++++++
 MAINTAINERS                                   |   5 +
 drivers/clocksource/Kconfig                   |  11 ++
 drivers/clocksource/Makefile                  |   1 +
 drivers/clocksource/timer-realtek.c           | 150 ++++++++++++++++++
 5 files changed, 214 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml
 create mode 100644 drivers/clocksource/timer-realtek.c


base-commit: 948b99877bf5a1cd58bee930e455b7574daba5c3
-- 
2.34.1

[PATCH v4 1/2] dt-bindings: timer: Add Realtek SYSTIMER

[Hao-Wen Ting]

The Realtek SYSTIMER (System Timer) is a 64-bit global hardware counter
operating at a fixed 1MHz frequency. Thanks to its compare match
interrupt capability, the timer natively supports oneshot mode for tick
broadcast functionality.

Signed-off-by: Hao-Wen Ting <haowen.ting@realtek.com>
---
 .../timer/realtek,rtd1625-systimer.yaml       | 47 +++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml

diff --git a/Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml b/Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml
new file mode 100644
index 000000000000..0b8fad37edb4
--- /dev/null
+++ b/Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml
@@ -0,0 +1,47 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/realtek,rtd1625-systimer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek System Timer
+
+maintainers:
+  - Hao-Wen Ting <haowen.ting@realtek.com>
+
+description: |
+  The Realtek SYSTIMER (System Timer) is a 64-bit global hardware counter operating
+  at a fixed 1MHz frequency. Thanks to its compare match interrupt capability,
+  the timer natively supports oneshot mode for tick broadcast functionality.
+
+properties:
+  compatible:
+    oneOf:
+      - const: realtek,rtd1625-systimer
+      - items:
+          - const: realtek,rtd1635-systimer
+          - const: realtek,rtd1625-systimer
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    timer@89420 {
+        compatible = "realtek,rtd1635-systimer",
+                     "realtek,rtd1625-systimer";
+        reg = <0x89420 0x18>;
+        interrupts = <GIC_SPI 112 IRQ_TYPE_LEVEL_HIGH>;
+    };
-- 
2.34.1

[PATCH v4 2/2] clocksource: Add Realtek system timer driver

[Hao-Wen Ting]

Add a system timer driver for Realtek SoCs.

This driver registers the 1 MHz global hardware counter on Realtek
platforms as a clock event device. Since this hardware counter starts
counting automatically after SoC power-on, no clock initialization is
required. Because the counter does not stop or get affected by CPU power
down, and it supports oneshot mode, it is typically used as a tick
broadcast timer.

Signed-off-by: Hao-Wen Ting <haowen.ting@realtek.com>
---
 MAINTAINERS                         |   5 +
 drivers/clocksource/Kconfig         |  11 ++
 drivers/clocksource/Makefile        |   1 +
 drivers/clocksource/timer-realtek.c | 150 ++++++++++++++++++++++++++++
 4 files changed, 167 insertions(+)
 create mode 100644 drivers/clocksource/timer-realtek.c

diff --git a/MAINTAINERS b/MAINTAINERS
index c7a116b795d5..90f511bb4982 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21670,6 +21670,11 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/spi/realtek,rtl9301-snand.yaml
 F:	drivers/spi/spi-realtek-rtl-snand.c
 
+REALTEK SYSTIMER DRIVER
+M:	Hao-Wen Ting <haowen.ting@realtek.com>
+S:	Maintained
+F:	drivers/clocksource/timer-realtek.c
+
 REALTEK WIRELESS DRIVER (rtlwifi family)
 M:	Ping-Ke Shih <pkshih@realtek.com>
 L:	linux-wireless@vger.kernel.org
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index ffcd23668763..aa59e5b13351 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -782,4 +782,15 @@ config NXP_STM_TIMER
           Enables the support for NXP System Timer Module found in the
           s32g NXP platform series.
 
+config RTK_SYSTIMER
+	bool "Realtek SYSTIMER support"
+	depends on ARM || ARM64
+	depends on ARCH_REALTEK || COMPILE_TEST
+	select TIMER_OF
+	help
+	  This option enables the driver that registers the global 1 MHz hardware
+	  counter as a clock event device on Realtek SoCs. Make sure to enable
+	  this option only when building for a Realtek platform or for compilation
+	  testing.
+
 endmenu
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index ec4452ee958f..b46376af6b49 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -95,3 +95,4 @@ obj-$(CONFIG_CLKSRC_LOONGSON1_PWM)	+= timer-loongson1-pwm.o
 obj-$(CONFIG_EP93XX_TIMER)		+= timer-ep93xx.o
 obj-$(CONFIG_RALINK_TIMER)		+= timer-ralink.o
 obj-$(CONFIG_NXP_STM_TIMER)		+= timer-nxp-stm.o
+obj-$(CONFIG_RTK_SYSTIMER)		+= timer-realtek.o
diff --git a/drivers/clocksource/timer-realtek.c b/drivers/clocksource/timer-realtek.c
new file mode 100644
index 000000000000..4f0439de9939
--- /dev/null
+++ b/drivers/clocksource/timer-realtek.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2025 Realtek Semiconductor Corp.
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/irqflags.h>
+#include <linux/interrupt.h>
+#include "timer-of.h"
+
+#define ENBL 1
+#define DSBL 0
+
+#define SYSTIMER_RATE 1000000
+#define SYSTIMER_MIN_DELTA 0x64
+#define SYSTIMER_MAX_DELTA ULONG_MAX
+
+/* SYSTIMER Register Offset (RTK Internal Use) */
+#define TS_LW_OFST 0x0
+#define TS_HW_OFST 0x4
+#define TS_CMP_VAL_LW_OFST 0x8
+#define TS_CMP_VAL_HW_OFST 0xC
+#define TS_CMP_CTRL_OFST 0x10
+#define TS_CMP_STAT_OFST 0x14
+
+/* SYSTIMER CMP CTRL REG Mask */
+#define TS_CMP_EN_MASK 0x1
+#define TS_WR_EN0_MASK 0x2
+
+static void __iomem *systimer_base;
+
+static u64 rtk_ts64_read(void)
+{
+	u32 low, high;
+	u64 ts;
+
+	/* Caution: Read LSB word (TS_LW_OFST) first then MSB (TS_HW_OFST) */
+	low = readl(systimer_base + TS_LW_OFST);
+	high = readl(systimer_base + TS_HW_OFST);
+	ts = ((u64)high << 32) | low;
+
+	return ts;
+}
+
+static void rtk_cmp_value_write(u64 value)
+{
+	u32 high, low;
+
+	low = value & 0xFFFFFFFF;
+	high = value >> 32;
+
+	writel(high, systimer_base + TS_CMP_VAL_HW_OFST);
+	writel(low, systimer_base + TS_CMP_VAL_LW_OFST);
+}
+
+static inline void rtk_cmp_en_write(bool cmp_en)
+{
+	u32 val;
+
+	val = TS_WR_EN0_MASK;
+	if (cmp_en == ENBL)
+		val |= TS_CMP_EN_MASK;
+
+	writel(val, systimer_base + TS_CMP_CTRL_OFST);
+}
+
+static int rtk_syst_clkevt_next_event(unsigned long cycles, struct clock_event_device *clkevt)
+{
+	u64 cmp_val;
+
+	rtk_cmp_en_write(DSBL);
+	cmp_val = rtk_ts64_read();
+
+	/* Set CMP value to current timestamp plus delta_us */
+	rtk_cmp_value_write(cmp_val + cycles);
+	rtk_cmp_en_write(ENBL);
+	return 0;
+}
+
+static irqreturn_t rtk_ts_match_intr_handler(int irq, void *dev_id)
+{
+	struct clock_event_device *clkevt = dev_id;
+	void __iomem *reg_base;
+	u32 val;
+
+	/* Disable TS CMP Match */
+	rtk_cmp_en_write(DSBL);
+
+	/* Clear TS CMP INTR */
+	reg_base = systimer_base + TS_CMP_STAT_OFST;
+	val = readl(reg_base) & TS_CMP_EN_MASK;
+	writel(val | TS_CMP_EN_MASK, reg_base);
+	clkevt->event_handler(clkevt);
+
+	return IRQ_HANDLED;
+}
+
+static int rtk_syst_shutdown(struct clock_event_device *clkevt)
+{
+	void __iomem *reg_base;
+	u64 cmp_val = 0;
+
+	/* Disable TS CMP Match */
+	rtk_cmp_en_write(DSBL);
+	/* Set compare value to 0 */
+	rtk_cmp_value_write(cmp_val);
+
+	/* Clear TS CMP INTR */
+	reg_base = systimer_base + TS_CMP_STAT_OFST;
+	writel(TS_CMP_EN_MASK, reg_base);
+	return 0;
+}
+
+static struct timer_of rtk_timer_to = {
+	.flags = TIMER_OF_IRQ | TIMER_OF_BASE,
+
+	.clkevt = {
+		.name			= "rtk-clkevt",
+		.rating			= 300,
+		.cpumask		= cpu_possible_mask,
+		.features		= CLOCK_EVT_FEAT_DYNIRQ |
+					  CLOCK_EVT_FEAT_ONESHOT,
+		.set_next_event		= rtk_syst_clkevt_next_event,
+		.set_state_oneshot	= rtk_syst_shutdown,
+		.set_state_shutdown	= rtk_syst_shutdown,
+	},
+
+	.of_irq = {
+		.flags			= IRQF_TIMER | IRQF_IRQPOLL,
+		.handler		= rtk_ts_match_intr_handler,
+	},
+};
+
+static int __init rtk_systimer_init(struct device_node *node)
+{
+	int ret;
+
+	ret = timer_of_init(node, &rtk_timer_to);
+	if (ret)
+		return ret;
+
+	systimer_base = timer_of_base(&rtk_timer_to);
+	clockevents_config_and_register(&rtk_timer_to.clkevt, SYSTIMER_RATE,
+					SYSTIMER_MIN_DELTA, SYSTIMER_MAX_DELTA);
+
+	return 0;
+}
+
+TIMER_OF_DECLARE(rtk_systimer, "realtek,rtd1625-systimer", rtk_systimer_init);
-- 
2.34.1

Re: [PATCH v4 1/2] dt-bindings: timer: Add Realtek SYSTIMER

[Krzysztof Kozlowski]

On Thu, Nov 20, 2025 at 02:30:09PM +0800, Hao-Wen Ting wrote:
> The Realtek SYSTIMER (System Timer) is a 64-bit global hardware counter
> operating at a fixed 1MHz frequency. Thanks to its compare match
> interrupt capability, the timer natively supports oneshot mode for tick
> broadcast functionality.
> 
> Signed-off-by: Hao-Wen Ting <haowen.ting@realtek.com>
> ---
>  .../timer/realtek,rtd1625-systimer.yaml       | 47 +++++++++++++++++++
>  1 file changed, 47 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml
> 
> diff --git a/Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml b/Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml
> new file mode 100644
> index 000000000000..0b8fad37edb4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml
> @@ -0,0 +1,47 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/timer/realtek,rtd1625-systimer.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Realtek System Timer
> +
> +maintainers:
> +  - Hao-Wen Ting <haowen.ting@realtek.com>
> +
> +description: |

Drop |. Do not need '|' unless you need to preserve formatting.

Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>

Best regards,
Krzysztof

Re: [PATCH v4 2/2] clocksource: Add Realtek system timer driver

[Thomas Gleixner]

On Thu, Nov 20 2025 at 14:30, Hao-Wen Ting wrote:
> Add a system timer driver for Realtek SoCs.
>
> This driver registers the 1 MHz global hardware counter on Realtek
> platforms as a clock event device. Since this hardware counter starts
> counting automatically after SoC power-on, no clock initialization is
> required. Because the counter does not stop or get affected by CPU power
> down, and it supports oneshot mode, it is typically used as a tick
> broadcast timer.
>
> Signed-off-by: Hao-Wen Ting <haowen.ting@realtek.com>

Acked-by: Thomas Gleixner <tglx@linutronix.de>