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Message-ID: <20251120063010.830805-3-haowen.ting@realtek.com>
Date: Thu, 20 Nov 2025 14:30:10 +0800
From: Hao-Wen Ting <haowen.ting@...ltek.com>
To: <daniel.lezcano@...aro.org>, <tglx@...utronix.de>
CC: <jinn.cheng@...ltek.com>, <edwardwu@...ltek.com>, <phelic@...ltek.com>,
<shawn.huang724@...ltek.com>, <haowen.ting@...ltek.com>,
<cy.huang@...ltek.com>, <james.tai@...ltek.com>, <cylee12@...ltek.com>,
<phinex@...ltek.com>, <conor+dt@...nel.org>, <krzk+dt@...nel.org>,
<robh@...nel.org>, <devicetree@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <stanley_chang@...ltek.com>
Subject: [PATCH v4 2/2] clocksource: Add Realtek system timer driver
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@...ltek.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@...ltek.com>
+S: Maintained
+F: drivers/clocksource/timer-realtek.c
+
REALTEK WIRELESS DRIVER (rtlwifi family)
M: Ping-Ke Shih <pkshih@...ltek.com>
L: linux-wireless@...r.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
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