[PATCH v4 0/3] Add the System Timer Module counter

[PATCH v4 0/3] Add the System Timer Module counter

[Daniel Lezcano]

The NXP S32 family provides a System Timer Module (STM), a 32-bit
free-running counter clocked from a peripheral clock. The STM includes
a prescaler and one or more compare channels generating optional
interrupts. When used as a generic hardware counter, only the main
free-running counter is required, while the compare channels are
typically unused.

On S32G2 devices, the STM is exposed as a simple counter block that
can operate continuously and be shared across subsystems such as the
Linux kernel, firmware components running on Cortex-M7 cores, or other
co-processors. The counter can be read atomically and provides a
stable timestamp source to correlate events occurring in different
execution contexts.

The Linux kernel controls the STM through a memory-mapped interface,
configuring the prescaler, enabling or disabling the counter, and
accounting for wrap-arounds. Other subsystems access the counter in
read-only mode, making it a shared timestamp reference across the
platform.

This driver adds support for the STM when used as a counter on S32G2
platforms. The device is described in the device tree using the
following compatible:

compatible = "nxp,s32g2-stm-cnt";

The driver exposes basic counter functionality: start, stop, reset,
prescaler configuration, and overflow handling.

Changelog:
	* v4
	  - Split context structure to suspend/resume
	  - Converted counter to a u64 to accumulate the time
	  - Replaced 'reset' to a count write to reset (William Breathitt Gray)
	  - Added events for userspace (William Breathitt Gray)
	  - Added action COUNTER_SYNAPSE_ACTION_RISING_EDGE for signal (William Breathitt Gray)
	  - Renamed counter name to "System Timer Module Counter" (William Breathitt Gray)

	* v3
	  - Fixed compatible typo "nxp,s32g2-stm" to "nxp,s32g2-stm-cnt"

	* v2
	  - Added Rob's tag
	  ** kbuild
	  - Reordered alphabetically the headers
	  - Added bitfield.h header
	  - Use DEFINE_SIMPLE_DEV_PM_OPS() and pm_sleep_ptr()

Daniel Lezcano (3):
  counters: Reorder the Makefile
  dt-bindings: counter: Add NXP System Timer Module Counter
  counter: Add STM based counter

 .../bindings/counter/nxp,s32g2-stm-cnt.yaml   |  64 +++
 arch/arm64/boot/dts/freescale/s32g2.dtsi      |   6 +-
 .../boot/dts/freescale/s32g274a-rdb2.dts      |  10 +-
 drivers/counter/Kconfig                       |  10 +
 drivers/counter/Makefile                      |  21 +-
 drivers/counter/nxp-stm-cnt.c                 | 433 ++++++++++++++++++
 6 files changed, 525 insertions(+), 19 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/counter/nxp,s32g2-stm-cnt.yaml
 create mode 100644 drivers/counter/nxp-stm-cnt.c

-- 
2.43.0

[PATCH v4 1/3] counters: Reorder the Makefile

[Daniel Lezcano]

The next changes provide a new driver. For the sake of clarity,
reorder the Makefile alphabetically.

No functional changes intended.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/counter/Makefile | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index fa3c1d08f706..40e644948e7a 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -6,14 +6,16 @@
 obj-$(CONFIG_COUNTER) += counter.o
 counter-y := counter-core.o counter-sysfs.o counter-chrdev.o
 
-obj-$(CONFIG_I8254)		+= i8254.o
-obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
+obj-$(CONFIG_104_QUAD_8)		+= 104-quad-8.o
+obj-$(CONFIG_FTM_QUADDEC)		+= ftm-quaddec.o
+obj-$(CONFIG_I8254)			+= i8254.o
+obj-$(CONFIG_INTEL_QEP)			+= intel-qep.o
 obj-$(CONFIG_INTERRUPT_CNT)		+= interrupt-cnt.o
-obj-$(CONFIG_RZ_MTU3_CNT)	+= rz-mtu3-cnt.o
-obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
-obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
-obj-$(CONFIG_TI_EQEP)		+= ti-eqep.o
-obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
 obj-$(CONFIG_MICROCHIP_TCB_CAPTURE)	+= microchip-tcb-capture.o
-obj-$(CONFIG_INTEL_QEP)		+= intel-qep.o
-obj-$(CONFIG_TI_ECAP_CAPTURE)	+= ti-ecap-capture.o
+obj-$(CONFIG_RZ_MTU3_CNT)		+= rz-mtu3-cnt.o
+obj-$(CONFIG_STM32_TIMER_CNT)		+= stm32-timer-cnt.o
+obj-$(CONFIG_STM32_LPTIMER_CNT)		+= stm32-lptimer-cnt.o
+obj-$(CONFIG_TI_ECAP_CAPTURE)		+= ti-ecap-capture.o
+obj-$(CONFIG_TI_EQEP)			+= ti-eqep.o
+
+
-- 
2.43.0

[PATCH v4 2/3] dt-bindings: counter: Add NXP System Timer Module Counter

[Daniel Lezcano]

Add the System Timer Module description found on the NXP s32 platform
when it is used as a counter and the compatible for the s32g2 variant.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 .../bindings/counter/nxp,s32g2-stm-cnt.yaml   | 64 +++++++++++++++++++
 arch/arm64/boot/dts/freescale/s32g2.dtsi      |  6 +-
 .../boot/dts/freescale/s32g274a-rdb2.dts      | 10 +--
 3 files changed, 70 insertions(+), 10 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/counter/nxp,s32g2-stm-cnt.yaml

diff --git a/Documentation/devicetree/bindings/counter/nxp,s32g2-stm-cnt.yaml b/Documentation/devicetree/bindings/counter/nxp,s32g2-stm-cnt.yaml
new file mode 100644
index 000000000000..4d42996f5ad3
--- /dev/null
+++ b/Documentation/devicetree/bindings/counter/nxp,s32g2-stm-cnt.yaml
@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/counter/nxp,s32g2-stm-cnt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP System Timer Module (STM)
+
+maintainers:
+  - Daniel Lezcano <daniel.lezcano@kernel.org>
+
+description:
+  The System Timer Module supports commonly required system and application
+  software timing functions. STM includes a 32-bit count-up timer and four
+  32-bit compare channels with a separate interrupt source for each channel.
+  The counter is driven by the STM module clock divided by an 8-bit prescale
+  value.
+
+properties:
+  compatible:
+    oneOf:
+      - const: nxp,s32g2-stm-cnt
+      - items:
+          - const: nxp,s32g3-stm-cnt
+          - const: nxp,s32g2-stm-cnt
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: Counter clock
+      - description: Module clock
+      - description: Register clock
+
+  clock-names:
+    items:
+      - const: counter
+      - const: module
+      - const: register
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    timer@4011c000 {
+        compatible = "nxp,s32g2-stm-cnt";
+        reg = <0x4011c000 0x3000>;
+        interrupts = <GIC_SPI 24 IRQ_TYPE_LEVEL_HIGH>;
+        clocks = <&clks 0x3b>, <&clks 0x3c>, <&clks 0x3c>;
+        clock-names = "counter", "module", "register";
+    };
diff --git a/arch/arm64/boot/dts/freescale/s32g2.dtsi b/arch/arm64/boot/dts/freescale/s32g2.dtsi
index 51d00dac12de..6bc0c75b574f 100644
--- a/arch/arm64/boot/dts/freescale/s32g2.dtsi
+++ b/arch/arm64/boot/dts/freescale/s32g2.dtsi
@@ -579,7 +579,7 @@ swt6: watchdog@40208000 {
 		};
 
 		stm4: timer@4021c000 {
-			compatible = "nxp,s32g2-stm";
+			compatible = "nxp,s32g2-stm-cnt";
 			reg = <0x4021c000 0x3000>;
 			clocks = <&clks 0x3b>, <&clks 0x3c>, <&clks 0x3c>;
 			clock-names = "counter", "module", "register";
@@ -588,7 +588,7 @@ stm4: timer@4021c000 {
 		};
 
 		stm5: timer@40220000 {
-			compatible = "nxp,s32g2-stm";
+			compatible = "nxp,s32g2-stm-cnt";
 			reg = <0x40220000 0x3000>;
 			clocks = <&clks 0x3b>, <&clks 0x3c>, <&clks 0x3c>;
 			clock-names = "counter", "module", "register";
@@ -597,7 +597,7 @@ stm5: timer@40220000 {
 		};
 
 		stm6: timer@40224000 {
-			compatible = "nxp,s32g2-stm";
+			compatible = "nxp,s32g2-stm-cnt";
 			reg = <0x40224000 0x3000>;
 			clocks = <&clks 0x3b>, <&clks 0x3c>, <&clks 0x3c>;
 			clock-names = "counter", "module", "register";
diff --git a/arch/arm64/boot/dts/freescale/s32g274a-rdb2.dts b/arch/arm64/boot/dts/freescale/s32g274a-rdb2.dts
index ee3121b192e5..bde5d3726825 100644
--- a/arch/arm64/boot/dts/freescale/s32g274a-rdb2.dts
+++ b/arch/arm64/boot/dts/freescale/s32g274a-rdb2.dts
@@ -41,19 +41,15 @@ &uart1 {
 	status = "okay";
 };
 
-&stm0 {
+&stm4 {
 	status = "okay";
 };
 
-&stm1 {
+&stm5 {
 	status = "okay";
 };
 
-&stm2 {
-	status = "okay";
-};
-
-&stm3 {
+&stm6 {
 	status = "okay";
 };
 
-- 
2.43.0

[PATCH v4 3/3] counter: Add STM based counter

[Daniel Lezcano]

The NXP S32G2 automotive platform integrates four Cortex-A53 cores and
three Cortex-M7 cores, along with a large number of timers and
counters. These hardware blocks can be used as clocksources or
clockevents, or as timestamp counters shared across the various
subsystems running alongside the Linux kernel, such as firmware
components. Their actual usage depends on the overall platform
software design.

In a Linux-based system, the kernel controls the counter, which is a
read-only shared resource for the other subsystems. One of its primary
purposes is to act as a common timestamp source for messages or
traces, allowing correlation of events occurring in different
operating system contexts.

These changes introduce a basic counter driver that can start, stop,
and reset the counter. It also handles overflow accounting and
configures the prescaler value.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/counter/Kconfig       |  10 +
 drivers/counter/Makefile      |   1 +
 drivers/counter/nxp-stm-cnt.c | 433 ++++++++++++++++++++++++++++++++++
 3 files changed, 444 insertions(+)
 create mode 100644 drivers/counter/nxp-stm-cnt.c

diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
index d30d22dfe577..bf5b281f194c 100644
--- a/drivers/counter/Kconfig
+++ b/drivers/counter/Kconfig
@@ -90,6 +90,16 @@ config MICROCHIP_TCB_CAPTURE
 	  To compile this driver as a module, choose M here: the
 	  module will be called microchip-tcb-capture.
 
+config NXP_STM_CNT
+	tristate "NXP System Timer Module Counter driver"
+	depends on ARCH_S32 || COMPILE_TEST
+	help
+	  Select this option to enable the NXP System Timer Module
+	  Counter driver.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called nxp_stm_cnt.
+
 config RZ_MTU3_CNT
 	tristate "Renesas RZ/G2L MTU3a counter driver"
 	depends on RZ_MTU3
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index 40e644948e7a..196b3c216875 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -12,6 +12,7 @@ obj-$(CONFIG_I8254)			+= i8254.o
 obj-$(CONFIG_INTEL_QEP)			+= intel-qep.o
 obj-$(CONFIG_INTERRUPT_CNT)		+= interrupt-cnt.o
 obj-$(CONFIG_MICROCHIP_TCB_CAPTURE)	+= microchip-tcb-capture.o
+obj-$(CONFIG_NXP_STM_CNT)		+= nxp-stm-cnt.o
 obj-$(CONFIG_RZ_MTU3_CNT)		+= rz-mtu3-cnt.o
 obj-$(CONFIG_STM32_TIMER_CNT)		+= stm32-timer-cnt.o
 obj-$(CONFIG_STM32_LPTIMER_CNT)		+= stm32-lptimer-cnt.o
diff --git a/drivers/counter/nxp-stm-cnt.c b/drivers/counter/nxp-stm-cnt.c
new file mode 100644
index 000000000000..9f2edd2161c8
--- /dev/null
+++ b/drivers/counter/nxp-stm-cnt.c
@@ -0,0 +1,433 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018,2021-2025 NXP
+ * Copyright 2025 Linaro Limited
+ *
+ * Author: Daniel Lezcano <daniel.lezcano@linaro.org>
+ *
+ * NXP S32G System Timer Module counters:
+ *
+ *  STM supports commonly required system and application software
+ *  timing functions. STM includes a 32-bit count-up timer and four
+ *  32-bit compare channels with a separate interrupt source for each
+ *  channel. The timer is driven by the STM module clock divided by an
+ *  8-bit prescale value (1 to 256). It has ability to stop the timer
+ *  in Debug mode
+ *
+ */
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/counter.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#define STM_CR(__base)		(__base)
+#define STM_CR_TEN		BIT(0)
+#define STM_CR_FRZ		BIT(1)
+#define STM_CR_CPS_MASK         GENMASK(15, 8)
+
+#define STM_CCR0(__base)	((__base) + 0x10)
+#define STM_CCR_CEN		BIT(0)
+
+#define STM_CIR0(__base)	((__base) + 0x14)
+#define STM_CIR_CIF		BIT(0)
+
+#define STM_CMP0(__base)	((__base) + 0x18)
+
+#define STM_CNT(__base)		((__base) + 0x04)
+
+#define STM_ENABLE_MASK	(STM_CR_FRZ | STM_CR_TEN)
+
+struct nxp_stm_context {
+	u32 counter;
+	u8 prescaler;
+	bool is_started;
+};
+
+struct nxp_stm_cnt {
+	spinlock_t lock; /* Protects counter */
+	void __iomem *base;
+	u64 counter;
+	struct nxp_stm_context context;
+};
+
+static void nxp_stm_cnt_enable(struct nxp_stm_cnt *stm_cnt)
+{
+	u32 reg;
+
+	reg = readl(STM_CR(stm_cnt->base));
+
+	reg |= STM_ENABLE_MASK;
+
+	writel(reg, STM_CR(stm_cnt->base));
+}
+
+static void nxp_stm_cnt_disable(struct nxp_stm_cnt *stm_cnt)
+{
+	u32 reg;
+
+	reg = readl(STM_CR(stm_cnt->base));
+
+	reg &= ~STM_ENABLE_MASK;
+
+	writel(reg, STM_CR(stm_cnt->base));
+}
+
+static void nxp_stm_cnt_ccr_disable(struct nxp_stm_cnt *stm_cnt)
+{
+	writel(0, STM_CCR0(stm_cnt->base));
+}
+
+static void nxp_stm_cnt_ccr_enable(struct nxp_stm_cnt *stm_cnt)
+{
+	writel(STM_CCR_CEN, STM_CCR0(stm_cnt->base));
+}
+
+static void nxp_stm_cnt_cfg_overflow(struct nxp_stm_cnt *stm_cnt)
+{
+	/*
+	 * The STM does not have a dedicated interrupt when the
+	 * counter wraps. We need to use the comparator to check if it
+	 * wrapped or not.
+	 */
+	writel(0, STM_CMP0(stm_cnt->base));
+}
+
+static u32 nxp_stm_cnt_get_counter(struct nxp_stm_cnt *stm_cnt)
+{
+	return readl(STM_CNT(stm_cnt->base));
+}
+
+static void nxp_stm_cnt_set_counter(struct nxp_stm_cnt *stm_cnt, u32 counter)
+{
+	writel(counter, STM_CNT(stm_cnt->base));
+}
+
+static void nxp_stm_cnt_set_prescaler(struct nxp_stm_cnt *stm_cnt, u8 prescaler)
+{
+	u32 reg;
+
+	reg = readl(STM_CR(stm_cnt->base));
+
+	FIELD_MODIFY(STM_CR_CPS_MASK, &reg, prescaler);
+
+	writel(reg, STM_CR(stm_cnt->base));
+}
+
+static u8 nxp_stm_cnt_get_prescaler(struct nxp_stm_cnt *stm_cnt)
+{
+	u32 reg = readl(STM_CR(stm_cnt->base));
+
+	return FIELD_GET(STM_CR_CPS_MASK, reg);
+}
+
+static bool nxp_stm_cnt_is_started(struct nxp_stm_cnt *stm_cnt)
+{
+	u32 reg;
+
+	reg = readl(STM_CR(stm_cnt->base));
+
+	return !!FIELD_GET(STM_CR_TEN, reg);
+}
+
+static void nxp_stm_cnt_irq_ack(struct nxp_stm_cnt *stm_cnt)
+{
+	writel(STM_CIR_CIF, STM_CIR0(stm_cnt->base));
+}
+
+static irqreturn_t nxp_stm_cnt_irq(int irq, void *dev_id)
+{
+	struct counter_device *counter = dev_id;
+	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
+
+	nxp_stm_cnt_irq_ack(stm_cnt);
+
+	counter_push_event(counter, COUNTER_EVENT_OVERFLOW, 0);
+
+	spin_lock(&stm_cnt->lock);
+	stm_cnt->counter += U32_MAX;
+	spin_unlock(&stm_cnt->lock);
+
+	return IRQ_HANDLED;
+}
+
+static void nxp_stm_cnt_start(struct nxp_stm_cnt *stm_cnt)
+{
+	nxp_stm_cnt_cfg_overflow(stm_cnt);
+	nxp_stm_cnt_enable(stm_cnt);
+	nxp_stm_cnt_ccr_enable(stm_cnt);
+}
+
+static void nxp_stm_cnt_stop(struct nxp_stm_cnt *stm_cnt)
+{
+	nxp_stm_cnt_disable(stm_cnt);
+	nxp_stm_cnt_irq_ack(stm_cnt);
+	nxp_stm_cnt_ccr_disable(stm_cnt);
+}
+
+static int nxp_stm_cnt_prescaler_read(struct counter_device *counter,
+				      struct counter_count *count, u8 *val)
+{
+	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
+
+	*val = nxp_stm_cnt_get_prescaler(stm_cnt);
+
+	return 0;
+}
+
+static int nxp_stm_cnt_prescaler_write(struct counter_device *counter,
+				       struct counter_count *count, u8 val)
+{
+	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
+
+	nxp_stm_cnt_set_prescaler(stm_cnt, val);
+
+	return 0;
+}
+
+static int nxp_stm_cnt_count_enable_write(struct counter_device *counter,
+					  struct counter_count *count, u8 enable)
+{
+	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
+
+	if (enable)
+		nxp_stm_cnt_start(stm_cnt);
+	else
+		nxp_stm_cnt_stop(stm_cnt);
+
+	return 0;
+}
+
+static int nxp_stm_cnt_count_enable_read(struct counter_device *counter,
+					 struct counter_count *count, u8 *enable)
+{
+	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
+
+	*enable = nxp_stm_cnt_is_started(stm_cnt);
+
+	return 0;
+}
+
+static struct counter_comp stm_cnt_count_ext[] = {
+	COUNTER_COMP_COUNT_U8("prescaler", nxp_stm_cnt_prescaler_read, nxp_stm_cnt_prescaler_write),
+	COUNTER_COMP_ENABLE(nxp_stm_cnt_count_enable_read, nxp_stm_cnt_count_enable_write),
+};
+
+static int nxp_stm_cnt_action_read(struct counter_device *counter,
+				   struct counter_count *count,
+				   struct counter_synapse *synapse,
+				   enum counter_synapse_action *action)
+{
+	*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
+
+	return 0;
+}
+
+static int nxp_stm_cnt_count_read(struct counter_device *dev,
+				  struct counter_count *count, u64 *val)
+{
+	struct nxp_stm_cnt *stm_cnt = counter_priv(dev);
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&stm_cnt->lock, irqflags);
+	*val = stm_cnt->counter + nxp_stm_cnt_get_counter(stm_cnt);
+	spin_unlock_irqrestore(&stm_cnt->lock, irqflags);
+
+	return 0;
+}
+
+static int nxp_stm_cnt_count_write(struct counter_device *dev,
+				   struct counter_count *count, u64 val)
+{
+	struct nxp_stm_cnt *stm_cnt = counter_priv(dev);
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&stm_cnt->lock, irqflags);
+	stm_cnt->counter = 0;
+	nxp_stm_cnt_set_counter(stm_cnt, 0);
+	spin_unlock_irqrestore(&stm_cnt->lock, irqflags);
+
+	return 0;
+}
+
+static const enum counter_function nxp_stm_cnt_functions[] = {
+	COUNTER_FUNCTION_INCREASE,
+};
+
+static int nxp_stm_cnt_function_read(struct counter_device *counter,
+				     struct counter_count *count,
+				     enum counter_function *function)
+{
+	*function = COUNTER_FUNCTION_INCREASE;
+
+	return 0;
+}
+
+static int nxp_stm_cnt_watch_validate(struct counter_device *counter,
+				      const struct counter_watch *watch)
+{
+	switch (watch->event) {
+	case COUNTER_EVENT_OVERFLOW:
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct counter_ops nxp_stm_cnt_counter_ops = {
+	.action_read = nxp_stm_cnt_action_read,
+	.count_read  = nxp_stm_cnt_count_read,
+	.count_write = nxp_stm_cnt_count_write,
+	.function_read = nxp_stm_cnt_function_read,
+	.watch_validate = nxp_stm_cnt_watch_validate,
+};
+
+static const enum counter_synapse_action nxp_stm_cnt_synapse_actions[] = {
+	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
+};
+
+static struct counter_signal nxp_stm_cnt_signals[] = {
+	{
+		.id = 0,
+		.name = "Counter wrap signal"
+	},
+};
+
+static struct counter_synapse nxp_stm_cnt_synapses[] = {
+	{
+		.actions_list = nxp_stm_cnt_synapse_actions,
+		.num_actions = ARRAY_SIZE(nxp_stm_cnt_synapse_actions),
+		.signal = &nxp_stm_cnt_signals[0],
+	},
+};
+
+static struct counter_count nxp_stm_cnt_counts[] = {
+	{
+		.id = 0,
+		.name = "System Timer Module Counter",
+		.synapses = nxp_stm_cnt_synapses,
+		.num_synapses = ARRAY_SIZE(nxp_stm_cnt_synapses),
+		.ext = stm_cnt_count_ext,
+		.num_ext = ARRAY_SIZE(stm_cnt_count_ext),
+	},
+};
+
+static int nxp_stm_cnt_suspend(struct device *dev)
+{
+	struct nxp_stm_cnt *stm_cnt = dev_get_drvdata(dev);
+
+	stm_cnt->context.is_started = nxp_stm_cnt_is_started(stm_cnt);
+
+	if (stm_cnt->context.is_started) {
+		nxp_stm_cnt_stop(stm_cnt);
+		stm_cnt->context.prescaler = nxp_stm_cnt_get_prescaler(stm_cnt);
+		stm_cnt->context.counter = nxp_stm_cnt_get_counter(stm_cnt);
+	}
+
+	return 0;
+}
+
+static int nxp_stm_cnt_resume(struct device *dev)
+{
+	struct nxp_stm_cnt *stm_cnt = dev_get_drvdata(dev);
+
+	if (stm_cnt->context.is_started) {
+		nxp_stm_cnt_set_counter(stm_cnt, stm_cnt->context.counter);
+		nxp_stm_cnt_set_prescaler(stm_cnt, stm_cnt->context.prescaler);
+		nxp_stm_cnt_start(stm_cnt);
+	}
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(nxp_stm_cnt_pm_ops, nxp_stm_cnt_suspend,
+				nxp_stm_cnt_resume);
+
+static int nxp_stm_cnt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct counter_device *counter;
+	struct nxp_stm_cnt *stm_cnt;
+	struct clk *clk;
+	void __iomem *base;
+	int irq, ret;
+
+	base = devm_of_iomap(dev, np, 0, NULL);
+	if (IS_ERR(base))
+		return dev_err_probe(dev, PTR_ERR(base), "Failed to iomap %pOFn\n", np);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return dev_err_probe(dev, irq, "Failed to get IRQ\n");
+
+	clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "Clock not found\n");
+
+	counter = devm_counter_alloc(dev, sizeof(*stm_cnt));
+	if (!counter)
+		return -ENOMEM;
+
+	stm_cnt = counter_priv(counter);
+
+	stm_cnt->base = base;
+	stm_cnt->counter = 0;
+	spin_lock_init(&stm_cnt->lock);
+
+	counter->name       = "stm_counter";
+	counter->parent     = &pdev->dev;
+	counter->ops        = &nxp_stm_cnt_counter_ops;
+	counter->counts     = nxp_stm_cnt_counts;
+	counter->num_counts = ARRAY_SIZE(nxp_stm_cnt_counts);
+
+	ret = devm_request_irq(dev, irq, nxp_stm_cnt_irq, IRQF_TIMER | IRQF_NOBALANCING,
+			       dev_name(&counter->dev), counter);
+	if (ret)
+		return dev_err_probe(dev, ret, "Unable to allocate interrupt line\n");
+
+	ret = devm_counter_add(dev, counter);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to register counter\n");
+
+	platform_set_drvdata(pdev, stm_cnt);
+
+	return 0;
+}
+
+static void nxp_stm_cnt_remove(struct platform_device *pdev)
+{
+	struct nxp_stm_cnt *stm_cnt = platform_get_drvdata(pdev);
+
+	if (nxp_stm_cnt_is_started(stm_cnt))
+		nxp_stm_cnt_stop(stm_cnt);
+}
+
+static const struct of_device_id nxp_stm_cnt_of_match[] = {
+	{ .compatible = "nxp,s32g2-stm-cnt", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, nxp_stm_cnt_of_match);
+
+static struct platform_driver nxp_stm_cnt_driver = {
+	.probe  = nxp_stm_cnt_probe,
+	.remove = nxp_stm_cnt_remove,
+	.driver = {
+		.name           = "nxp-stm-cnt",
+		.pm		= pm_sleep_ptr(&nxp_stm_cnt_pm_ops),
+		.of_match_table = nxp_stm_cnt_of_match,
+	},
+};
+module_platform_driver(nxp_stm_cnt_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Daniel Lezcano");
+MODULE_DESCRIPTION("NXP System Timer Module counter driver");
+MODULE_IMPORT_NS("COUNTER");
-- 
2.43.0

Re: [PATCH v4 3/3] counter: Add STM based counter

[Frank Li]

On Wed, Jan 07, 2026 at 02:39:52PM +0100, Daniel Lezcano wrote:
> The NXP S32G2 automotive platform integrates four Cortex-A53 cores and
> three Cortex-M7 cores, along with a large number of timers and
> counters. These hardware blocks can be used as clocksources or
> clockevents, or as timestamp counters shared across the various
> subsystems running alongside the Linux kernel, such as firmware
> components. Their actual usage depends on the overall platform
> software design.
>
> In a Linux-based system, the kernel controls the counter, which is a
> read-only shared resource for the other subsystems. One of its primary
> purposes is to act as a common timestamp source for messages or
> traces, allowing correlation of events occurring in different
> operating system contexts.
>
> These changes introduce a basic counter driver that can start, stop,
> and reset the counter. It also handles overflow accounting and
> configures the prescaler value.
>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---
>  drivers/counter/Kconfig       |  10 +
>  drivers/counter/Makefile      |   1 +
>  drivers/counter/nxp-stm-cnt.c | 433 ++++++++++++++++++++++++++++++++++
>  3 files changed, 444 insertions(+)
>  create mode 100644 drivers/counter/nxp-stm-cnt.c
>
> diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
> index d30d22dfe577..bf5b281f194c 100644
> --- a/drivers/counter/Kconfig
> +++ b/drivers/counter/Kconfig
> @@ -90,6 +90,16 @@ config MICROCHIP_TCB_CAPTURE
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called microchip-tcb-capture.
>
> +config NXP_STM_CNT
> +	tristate "NXP System Timer Module Counter driver"
> +	depends on ARCH_S32 || COMPILE_TEST
> +	help
> +	  Select this option to enable the NXP System Timer Module
> +	  Counter driver.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called nxp_stm_cnt.
> +
>  config RZ_MTU3_CNT
>  	tristate "Renesas RZ/G2L MTU3a counter driver"
>  	depends on RZ_MTU3
> diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
> index 40e644948e7a..196b3c216875 100644
> --- a/drivers/counter/Makefile
> +++ b/drivers/counter/Makefile
> @@ -12,6 +12,7 @@ obj-$(CONFIG_I8254)			+= i8254.o
>  obj-$(CONFIG_INTEL_QEP)			+= intel-qep.o
>  obj-$(CONFIG_INTERRUPT_CNT)		+= interrupt-cnt.o
>  obj-$(CONFIG_MICROCHIP_TCB_CAPTURE)	+= microchip-tcb-capture.o
> +obj-$(CONFIG_NXP_STM_CNT)		+= nxp-stm-cnt.o
>  obj-$(CONFIG_RZ_MTU3_CNT)		+= rz-mtu3-cnt.o
>  obj-$(CONFIG_STM32_TIMER_CNT)		+= stm32-timer-cnt.o
>  obj-$(CONFIG_STM32_LPTIMER_CNT)		+= stm32-lptimer-cnt.o
> diff --git a/drivers/counter/nxp-stm-cnt.c b/drivers/counter/nxp-stm-cnt.c
> new file mode 100644
> index 000000000000..9f2edd2161c8
> --- /dev/null
> +++ b/drivers/counter/nxp-stm-cnt.c
> @@ -0,0 +1,433 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2018,2021-2025 NXP
> + * Copyright 2025 Linaro Limited
> + *
> + * Author: Daniel Lezcano <daniel.lezcano@linaro.org>
> + *
> + * NXP S32G System Timer Module counters:
> + *
> + *  STM supports commonly required system and application software
> + *  timing functions. STM includes a 32-bit count-up timer and four
> + *  32-bit compare channels with a separate interrupt source for each
> + *  channel. The timer is driven by the STM module clock divided by an
> + *  8-bit prescale value (1 to 256). It has ability to stop the timer
> + *  in Debug mode
> + *
> + */
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/counter.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +
> +#define STM_CR(__base)		(__base)
> +#define STM_CR_TEN		BIT(0)
> +#define STM_CR_FRZ		BIT(1)
> +#define STM_CR_CPS_MASK         GENMASK(15, 8)
> +
> +#define STM_CCR0(__base)	((__base) + 0x10)
> +#define STM_CCR_CEN		BIT(0)
> +
> +#define STM_CIR0(__base)	((__base) + 0x14)
> +#define STM_CIR_CIF		BIT(0)
> +
> +#define STM_CMP0(__base)	((__base) + 0x18)
> +
> +#define STM_CNT(__base)		((__base) + 0x04)
> +
> +#define STM_ENABLE_MASK	(STM_CR_FRZ | STM_CR_TEN)
> +
> +struct nxp_stm_context {
> +	u32 counter;
> +	u8 prescaler;
> +	bool is_started;
> +};
> +
> +struct nxp_stm_cnt {
> +	spinlock_t lock; /* Protects counter */
> +	void __iomem *base;
> +	u64 counter;
> +	struct nxp_stm_context context;
> +};
> +
> +static void nxp_stm_cnt_enable(struct nxp_stm_cnt *stm_cnt)
> +{
> +	u32 reg;
> +
> +	reg = readl(STM_CR(stm_cnt->base));
> +
> +	reg |= STM_ENABLE_MASK;
> +
> +	writel(reg, STM_CR(stm_cnt->base));
> +}
> +
> +static void nxp_stm_cnt_disable(struct nxp_stm_cnt *stm_cnt)
> +{
> +	u32 reg;
> +
> +	reg = readl(STM_CR(stm_cnt->base));
> +
> +	reg &= ~STM_ENABLE_MASK;
> +
> +	writel(reg, STM_CR(stm_cnt->base));
> +}
> +
> +static void nxp_stm_cnt_ccr_disable(struct nxp_stm_cnt *stm_cnt)
> +{
> +	writel(0, STM_CCR0(stm_cnt->base));
> +}
> +
> +static void nxp_stm_cnt_ccr_enable(struct nxp_stm_cnt *stm_cnt)
> +{
> +	writel(STM_CCR_CEN, STM_CCR0(stm_cnt->base));
> +}
> +
> +static void nxp_stm_cnt_cfg_overflow(struct nxp_stm_cnt *stm_cnt)
> +{
> +	/*
> +	 * The STM does not have a dedicated interrupt when the
> +	 * counter wraps. We need to use the comparator to check if it
> +	 * wrapped or not.
> +	 */
> +	writel(0, STM_CMP0(stm_cnt->base));
> +}
> +
> +static u32 nxp_stm_cnt_get_counter(struct nxp_stm_cnt *stm_cnt)
> +{
> +	return readl(STM_CNT(stm_cnt->base));
> +}
> +
> +static void nxp_stm_cnt_set_counter(struct nxp_stm_cnt *stm_cnt, u32 counter)
> +{
> +	writel(counter, STM_CNT(stm_cnt->base));
> +}
> +
> +static void nxp_stm_cnt_set_prescaler(struct nxp_stm_cnt *stm_cnt, u8 prescaler)
> +{
> +	u32 reg;
> +
> +	reg = readl(STM_CR(stm_cnt->base));
> +
> +	FIELD_MODIFY(STM_CR_CPS_MASK, &reg, prescaler);
> +
> +	writel(reg, STM_CR(stm_cnt->base));
> +}
> +
> +static u8 nxp_stm_cnt_get_prescaler(struct nxp_stm_cnt *stm_cnt)
> +{
> +	u32 reg = readl(STM_CR(stm_cnt->base));
> +
> +	return FIELD_GET(STM_CR_CPS_MASK, reg);
> +}
> +
> +static bool nxp_stm_cnt_is_started(struct nxp_stm_cnt *stm_cnt)
> +{
> +	u32 reg;
> +
> +	reg = readl(STM_CR(stm_cnt->base));
> +
> +	return !!FIELD_GET(STM_CR_TEN, reg);
> +}
> +
> +static void nxp_stm_cnt_irq_ack(struct nxp_stm_cnt *stm_cnt)
> +{
> +	writel(STM_CIR_CIF, STM_CIR0(stm_cnt->base));
> +}
> +
> +static irqreturn_t nxp_stm_cnt_irq(int irq, void *dev_id)
> +{
> +	struct counter_device *counter = dev_id;
> +	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
> +
> +	nxp_stm_cnt_irq_ack(stm_cnt);
> +
> +	counter_push_event(counter, COUNTER_EVENT_OVERFLOW, 0);
> +
> +	spin_lock(&stm_cnt->lock);
> +	stm_cnt->counter += U32_MAX;
> +	spin_unlock(&stm_cnt->lock);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void nxp_stm_cnt_start(struct nxp_stm_cnt *stm_cnt)
> +{
> +	nxp_stm_cnt_cfg_overflow(stm_cnt);
> +	nxp_stm_cnt_enable(stm_cnt);
> +	nxp_stm_cnt_ccr_enable(stm_cnt);
> +}
> +
> +static void nxp_stm_cnt_stop(struct nxp_stm_cnt *stm_cnt)
> +{
> +	nxp_stm_cnt_disable(stm_cnt);
> +	nxp_stm_cnt_irq_ack(stm_cnt);
> +	nxp_stm_cnt_ccr_disable(stm_cnt);
> +}
> +
> +static int nxp_stm_cnt_prescaler_read(struct counter_device *counter,
> +				      struct counter_count *count, u8 *val)
> +{
> +	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
> +
> +	*val = nxp_stm_cnt_get_prescaler(stm_cnt);
> +
> +	return 0;
> +}
> +
> +static int nxp_stm_cnt_prescaler_write(struct counter_device *counter,
> +				       struct counter_count *count, u8 val)
> +{
> +	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
> +
> +	nxp_stm_cnt_set_prescaler(stm_cnt, val);
> +
> +	return 0;
> +}
> +
> +static int nxp_stm_cnt_count_enable_write(struct counter_device *counter,
> +					  struct counter_count *count, u8 enable)
> +{
> +	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
> +
> +	if (enable)
> +		nxp_stm_cnt_start(stm_cnt);
> +	else
> +		nxp_stm_cnt_stop(stm_cnt);
> +
> +	return 0;
> +}
> +
> +static int nxp_stm_cnt_count_enable_read(struct counter_device *counter,
> +					 struct counter_count *count, u8 *enable)
> +{
> +	struct nxp_stm_cnt *stm_cnt = counter_priv(counter);
> +
> +	*enable = nxp_stm_cnt_is_started(stm_cnt);
> +
> +	return 0;
> +}
> +
> +static struct counter_comp stm_cnt_count_ext[] = {
> +	COUNTER_COMP_COUNT_U8("prescaler", nxp_stm_cnt_prescaler_read, nxp_stm_cnt_prescaler_write),
> +	COUNTER_COMP_ENABLE(nxp_stm_cnt_count_enable_read, nxp_stm_cnt_count_enable_write),
> +};
> +
> +static int nxp_stm_cnt_action_read(struct counter_device *counter,
> +				   struct counter_count *count,
> +				   struct counter_synapse *synapse,
> +				   enum counter_synapse_action *action)
> +{
> +	*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
> +
> +	return 0;
> +}
> +
> +static int nxp_stm_cnt_count_read(struct counter_device *dev,
> +				  struct counter_count *count, u64 *val)
> +{
> +	struct nxp_stm_cnt *stm_cnt = counter_priv(dev);
> +	unsigned long irqflags;
> +
> +	spin_lock_irqsave(&stm_cnt->lock, irqflags);
> +	*val = stm_cnt->counter + nxp_stm_cnt_get_counter(stm_cnt);
> +	spin_unlock_irqrestore(&stm_cnt->lock, irqflags);

It think there are still rise condition here.

cpu 0                                            cpu 1
1:  nxp_stm_cnt_get_counter(stm_cnt); (0)
2: 						 irq_handle()
					         counter += INT_MAX;
3:

when wrap happen, nxp_stm_cnt_get_counter() return 0, but, irq still not
handle yet.

so nxp_stm_cnt_count_read() return 0 at 1.

it return INT_MAX at 3 suddently.

Frank
> +
> +	return 0;
> +}
> +
> +static int nxp_stm_cnt_count_write(struct counter_device *dev,
> +				   struct counter_count *count, u64 val)
> +{
> +	struct nxp_stm_cnt *stm_cnt = counter_priv(dev);
> +	unsigned long irqflags;
> +
> +	spin_lock_irqsave(&stm_cnt->lock, irqflags);
> +	stm_cnt->counter = 0;
> +	nxp_stm_cnt_set_counter(stm_cnt, 0);
> +	spin_unlock_irqrestore(&stm_cnt->lock, irqflags);
> +
> +	return 0;
> +}
> +
> +static const enum counter_function nxp_stm_cnt_functions[] = {
> +	COUNTER_FUNCTION_INCREASE,
> +};
> +
> +static int nxp_stm_cnt_function_read(struct counter_device *counter,
> +				     struct counter_count *count,
> +				     enum counter_function *function)
> +{
> +	*function = COUNTER_FUNCTION_INCREASE;
> +
> +	return 0;
> +}
> +
> +static int nxp_stm_cnt_watch_validate(struct counter_device *counter,
> +				      const struct counter_watch *watch)
> +{
> +	switch (watch->event) {
> +	case COUNTER_EVENT_OVERFLOW:
> +		return 0;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct counter_ops nxp_stm_cnt_counter_ops = {
> +	.action_read = nxp_stm_cnt_action_read,
> +	.count_read  = nxp_stm_cnt_count_read,
> +	.count_write = nxp_stm_cnt_count_write,
> +	.function_read = nxp_stm_cnt_function_read,
> +	.watch_validate = nxp_stm_cnt_watch_validate,
> +};
> +
> +static const enum counter_synapse_action nxp_stm_cnt_synapse_actions[] = {
> +	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
> +};
> +
> +static struct counter_signal nxp_stm_cnt_signals[] = {
> +	{
> +		.id = 0,
> +		.name = "Counter wrap signal"
> +	},
> +};
> +
> +static struct counter_synapse nxp_stm_cnt_synapses[] = {
> +	{
> +		.actions_list = nxp_stm_cnt_synapse_actions,
> +		.num_actions = ARRAY_SIZE(nxp_stm_cnt_synapse_actions),
> +		.signal = &nxp_stm_cnt_signals[0],
> +	},
> +};
> +
> +static struct counter_count nxp_stm_cnt_counts[] = {
> +	{
> +		.id = 0,
> +		.name = "System Timer Module Counter",
> +		.synapses = nxp_stm_cnt_synapses,
> +		.num_synapses = ARRAY_SIZE(nxp_stm_cnt_synapses),
> +		.ext = stm_cnt_count_ext,
> +		.num_ext = ARRAY_SIZE(stm_cnt_count_ext),
> +	},
> +};
> +
> +static int nxp_stm_cnt_suspend(struct device *dev)
> +{
> +	struct nxp_stm_cnt *stm_cnt = dev_get_drvdata(dev);
> +
> +	stm_cnt->context.is_started = nxp_stm_cnt_is_started(stm_cnt);
> +
> +	if (stm_cnt->context.is_started) {
> +		nxp_stm_cnt_stop(stm_cnt);
> +		stm_cnt->context.prescaler = nxp_stm_cnt_get_prescaler(stm_cnt);
> +		stm_cnt->context.counter = nxp_stm_cnt_get_counter(stm_cnt);
> +	}
> +
> +	return 0;
> +}
> +
> +static int nxp_stm_cnt_resume(struct device *dev)
> +{
> +	struct nxp_stm_cnt *stm_cnt = dev_get_drvdata(dev);
> +
> +	if (stm_cnt->context.is_started) {
> +		nxp_stm_cnt_set_counter(stm_cnt, stm_cnt->context.counter);
> +		nxp_stm_cnt_set_prescaler(stm_cnt, stm_cnt->context.prescaler);
> +		nxp_stm_cnt_start(stm_cnt);
> +	}
> +
> +	return 0;
> +}
> +
> +static DEFINE_SIMPLE_DEV_PM_OPS(nxp_stm_cnt_pm_ops, nxp_stm_cnt_suspend,
> +				nxp_stm_cnt_resume);
> +
> +static int nxp_stm_cnt_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np = dev->of_node;
> +	struct counter_device *counter;
> +	struct nxp_stm_cnt *stm_cnt;
> +	struct clk *clk;
> +	void __iomem *base;
> +	int irq, ret;
> +
> +	base = devm_of_iomap(dev, np, 0, NULL);
> +	if (IS_ERR(base))
> +		return dev_err_probe(dev, PTR_ERR(base), "Failed to iomap %pOFn\n", np);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return dev_err_probe(dev, irq, "Failed to get IRQ\n");
> +
> +	clk = devm_clk_get_enabled(dev, NULL);
> +	if (IS_ERR(clk))
> +		return dev_err_probe(dev, PTR_ERR(clk), "Clock not found\n");
> +
> +	counter = devm_counter_alloc(dev, sizeof(*stm_cnt));
> +	if (!counter)
> +		return -ENOMEM;
> +
> +	stm_cnt = counter_priv(counter);
> +
> +	stm_cnt->base = base;
> +	stm_cnt->counter = 0;
> +	spin_lock_init(&stm_cnt->lock);
> +
> +	counter->name       = "stm_counter";
> +	counter->parent     = &pdev->dev;
> +	counter->ops        = &nxp_stm_cnt_counter_ops;
> +	counter->counts     = nxp_stm_cnt_counts;
> +	counter->num_counts = ARRAY_SIZE(nxp_stm_cnt_counts);
> +
> +	ret = devm_request_irq(dev, irq, nxp_stm_cnt_irq, IRQF_TIMER | IRQF_NOBALANCING,
> +			       dev_name(&counter->dev), counter);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Unable to allocate interrupt line\n");
> +
> +	ret = devm_counter_add(dev, counter);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to register counter\n");
> +
> +	platform_set_drvdata(pdev, stm_cnt);
> +
> +	return 0;
> +}
> +
> +static void nxp_stm_cnt_remove(struct platform_device *pdev)
> +{
> +	struct nxp_stm_cnt *stm_cnt = platform_get_drvdata(pdev);
> +
> +	if (nxp_stm_cnt_is_started(stm_cnt))
> +		nxp_stm_cnt_stop(stm_cnt);
> +}
> +
> +static const struct of_device_id nxp_stm_cnt_of_match[] = {
> +	{ .compatible = "nxp,s32g2-stm-cnt", },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, nxp_stm_cnt_of_match);
> +
> +static struct platform_driver nxp_stm_cnt_driver = {
> +	.probe  = nxp_stm_cnt_probe,
> +	.remove = nxp_stm_cnt_remove,
> +	.driver = {
> +		.name           = "nxp-stm-cnt",
> +		.pm		= pm_sleep_ptr(&nxp_stm_cnt_pm_ops),
> +		.of_match_table = nxp_stm_cnt_of_match,
> +	},
> +};
> +module_platform_driver(nxp_stm_cnt_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Daniel Lezcano");
> +MODULE_DESCRIPTION("NXP System Timer Module counter driver");
> +MODULE_IMPORT_NS("COUNTER");
> --
> 2.43.0
>

Re: [PATCH v4 3/3] counter: Add STM based counter

[Daniel Lezcano]

On 1/8/26 17:41, Frank Li wrote:
> On Wed, Jan 07, 2026 at 02:39:52PM +0100, Daniel Lezcano wrote:
>> The NXP S32G2 automotive platform integrates four Cortex-A53 cores and
>> three Cortex-M7 cores, along with a large number of timers and
>> counters. These hardware blocks can be used as clocksources or
>> clockevents, or as timestamp counters shared across the various
>> subsystems running alongside the Linux kernel, such as firmware
>> components. Their actual usage depends on the overall platform
>> software design.
>>
>> In a Linux-based system, the kernel controls the counter, which is a
>> read-only shared resource for the other subsystems. One of its primary
>> purposes is to act as a common timestamp source for messages or
>> traces, allowing correlation of events occurring in different
>> operating system contexts.
>>
>> These changes introduce a basic counter driver that can start, stop,
>> and reset the counter. It also handles overflow accounting and
>> configures the prescaler value.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
>> ---

[ ... ]

>> +
>> +static struct counter_comp stm_cnt_count_ext[] = {
>> +	COUNTER_COMP_COUNT_U8("prescaler", nxp_stm_cnt_prescaler_read, nxp_stm_cnt_prescaler_write),
>> +	COUNTER_COMP_ENABLE(nxp_stm_cnt_count_enable_read, nxp_stm_cnt_count_enable_write),
>> +};
>> +
>> +static int nxp_stm_cnt_action_read(struct counter_device *counter,
>> +				   struct counter_count *count,
>> +				   struct counter_synapse *synapse,
>> +				   enum counter_synapse_action *action)
>> +{
>> +	*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
>> +
>> +	return 0;
>> +}
>> +
>> +static int nxp_stm_cnt_count_read(struct counter_device *dev,
>> +				  struct counter_count *count, u64 *val)
>> +{
>> +	struct nxp_stm_cnt *stm_cnt = counter_priv(dev);
>> +	unsigned long irqflags;
>> +
>> +	spin_lock_irqsave(&stm_cnt->lock, irqflags);
>> +	*val = stm_cnt->counter + nxp_stm_cnt_get_counter(stm_cnt);
>> +	spin_unlock_irqrestore(&stm_cnt->lock, irqflags);
> 
> It think there are still rise condition here.
> 
> cpu 0                                            cpu 1
> 1:  nxp_stm_cnt_get_counter(stm_cnt); (0)
> 2: 						 irq_handle()
> 					         counter += INT_MAX;
> 3:
> 
> when wrap happen, nxp_stm_cnt_get_counter() return 0, but, irq still not
> handle yet.
> 
> so nxp_stm_cnt_count_read() return 0 at 1.
> 
> it return INT_MAX at 3 suddently.

Thanks for the review. Yes, it seems like there is a race for the reader 
result.

Except disabling / enabling the counter when reading the value, I don't 
see how to handle that case.



bool is_started = nxp_stm_cnt_is_started(stm_cnt);

if (is_started)
	nxp_stm_cnt_disable(stm_cnt);

/* If the counter wrapped, the interrupt fired already */

spin_lock_irqsave(&stm_cnt->lock, irqflags);

/* Counter can be zero (or more), we don't care, UINT_MAX was added */
*val = stm_cnt->counter + nxp_stm_cnt_get_counter(stm_cnt);

spin_unlock_irqrestore(&stm_cnt->lock, irqflags);

if (is_started)
	nxp_stm_cnt_enable(stm_cnt);





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Re: [PATCH v4 3/3] counter: Add STM based counter

[Frank Li]

On Thu, Jan 08, 2026 at 06:11:28PM +0100, Daniel Lezcano wrote:
> On 1/8/26 17:41, Frank Li wrote:
> > On Wed, Jan 07, 2026 at 02:39:52PM +0100, Daniel Lezcano wrote:
> > > The NXP S32G2 automotive platform integrates four Cortex-A53 cores and
> > > three Cortex-M7 cores, along with a large number of timers and
> > > counters. These hardware blocks can be used as clocksources or
> > > clockevents, or as timestamp counters shared across the various
> > > subsystems running alongside the Linux kernel, such as firmware
> > > components. Their actual usage depends on the overall platform
> > > software design.
> > >
> > > In a Linux-based system, the kernel controls the counter, which is a
> > > read-only shared resource for the other subsystems. One of its primary
> > > purposes is to act as a common timestamp source for messages or
> > > traces, allowing correlation of events occurring in different
> > > operating system contexts.
> > >
> > > These changes introduce a basic counter driver that can start, stop,
> > > and reset the counter. It also handles overflow accounting and
> > > configures the prescaler value.
> > >
> > > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> > > ---
>
> [ ... ]
>
> > > +
> > > +static struct counter_comp stm_cnt_count_ext[] = {
> > > +	COUNTER_COMP_COUNT_U8("prescaler", nxp_stm_cnt_prescaler_read, nxp_stm_cnt_prescaler_write),
> > > +	COUNTER_COMP_ENABLE(nxp_stm_cnt_count_enable_read, nxp_stm_cnt_count_enable_write),
> > > +};
> > > +
> > > +static int nxp_stm_cnt_action_read(struct counter_device *counter,
> > > +				   struct counter_count *count,
> > > +				   struct counter_synapse *synapse,
> > > +				   enum counter_synapse_action *action)
> > > +{
> > > +	*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int nxp_stm_cnt_count_read(struct counter_device *dev,
> > > +				  struct counter_count *count, u64 *val)
> > > +{
> > > +	struct nxp_stm_cnt *stm_cnt = counter_priv(dev);
> > > +	unsigned long irqflags;
> > > +
> > > +	spin_lock_irqsave(&stm_cnt->lock, irqflags);
> > > +	*val = stm_cnt->counter + nxp_stm_cnt_get_counter(stm_cnt);
> > > +	spin_unlock_irqrestore(&stm_cnt->lock, irqflags);
> >
> > It think there are still rise condition here.
> >
> > cpu 0                                            cpu 1
> > 1:  nxp_stm_cnt_get_counter(stm_cnt); (0)
> > 2: 						 irq_handle()
> > 					         counter += INT_MAX;
> > 3:
> >
> > when wrap happen, nxp_stm_cnt_get_counter() return 0, but, irq still not
> > handle yet.
> >
> > so nxp_stm_cnt_count_read() return 0 at 1.
> >
> > it return INT_MAX at 3 suddently.
>
> Thanks for the review. Yes, it seems like there is a race for the reader
> result.
>
> Except disabling / enabling the counter when reading the value, I don't see
> how to handle that case.
>

I think needn't handler overflow at all.
See stm32_count_function_read()

comparor always is u32 val + delta.  it can work if delta less U32_MAX/2.

If you real want to up to 64bit counter, perf counter have common solution
for that

x_counter()
{
	u32 v = readl():
	stm->count += v - stm->last;
	stm->last = v;
}

you need enable irq, make sure at call x_counter() twice during counter
wrap period.

No lock, no stop needed.

Frank

>
>
> bool is_started = nxp_stm_cnt_is_started(stm_cnt);
>
> if (is_started)
> 	nxp_stm_cnt_disable(stm_cnt);
>
> /* If the counter wrapped, the interrupt fired already */
>
> spin_lock_irqsave(&stm_cnt->lock, irqflags);
>
> /* Counter can be zero (or more), we don't care, UINT_MAX was added */
> *val = stm_cnt->counter + nxp_stm_cnt_get_counter(stm_cnt);
>
> spin_unlock_irqrestore(&stm_cnt->lock, irqflags);
>
> if (is_started)
> 	nxp_stm_cnt_enable(stm_cnt);
>
>
>
>
>
> --
> <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
>
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