[PATCH 1/2] clocksource: add ARMv7-M SysTick driver

[PATCH 1/2] clocksource: add ARMv7-M SysTick driver

[Ahmad Fatoum]

The SysTick is a simple 24-bit system timer that's required for ARMv7-M
implementations. Add a clocksource driver for it for Cortex-M system
support.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/clocksource/Kconfig          |  5 ++
 drivers/clocksource/Makefile         |  1 +
 drivers/clocksource/armv7m_systick.c | 87 ++++++++++++++++++++++++++++
 3 files changed, 93 insertions(+)
 create mode 100644 drivers/clocksource/armv7m_systick.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index c6ca72d4e927..9fae1f2d352e 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -115,4 +115,9 @@ config CLINT_TIMER
 	  This option enables the CLINT timer for RISC-V systems.  The CLINT
 	  driver is usually used for NoMMU RISC-V systems.
 
+config ARMV7M_SYSTICK
+	bool "Support for the ARMv7M system timer" if COMPILE_TEST
+	help
+	  This option enables support for the ARMv7M system timer unit.
+
 endmenu
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 21fd83a0930b..a4a7b84fae0c 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -24,3 +24,4 @@ obj-$(CONFIG_CLOCKSOURCE_TI_DM) += timer-ti-dm.o
 obj-$(CONFIG_CLOCKSOURCE_TI_32K) += timer-ti-32k.o
 obj-$(CONFIG_CLINT_TIMER) += timer-clint.o
 obj-$(CONFIG_RISCV_TIMER) += timer-riscv.o
+obj-$(CONFIG_ARMV7M_SYSTICK) += armv7m_systick.o
diff --git a/drivers/clocksource/armv7m_systick.c b/drivers/clocksource/armv7m_systick.c
new file mode 100644
index 000000000000..5f9222c50b8a
--- /dev/null
+++ b/drivers/clocksource/armv7m_systick.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) Maxime Coquelin 2015
+ * Author:  Maxime Coquelin <mcoquelin.stm32@gmail.com>
+ */
+
+#include <common.h>
+#include <init.h>
+#include <clock.h>
+#include <io.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+
+#define SYST_CSR	0x00
+#define SYST_RVR	0x04
+#define SYST_CVR	0x08
+#define SYST_CALIB	0x0c
+
+#define SYSTICK_CTRL_EN		BIT(0)
+/* Clock source: 0 = Ref clock, 1 = CPU clock */
+#define SYSTICK_CTRL_CPU_CLK	BIT(2)
+#define SYSTICK_CAL_NOREF	BIT(31)
+
+#define SYSTICK_LOAD_RELOAD_MASK 0x00FFFFFF
+
+static __iomem void *systick_base;
+
+static u64 armv7m_systick_clocksource_read(void)
+{
+        return SYSTICK_LOAD_RELOAD_MASK - readl(systick_base + SYST_CVR);
+}
+
+static struct clocksource cs = {
+	.read	= armv7m_systick_clocksource_read,
+	.mask	= CLOCKSOURCE_MASK(24),
+	.shift	= 0,
+};
+
+static int armv7m_systick_probe(struct device_d *dev)
+{
+	struct clk *clk = NULL;
+	u32 rate, cal;
+	int ret;
+
+	systick_base = dev_request_mem_region_err_null(dev, 0);
+	if (!systick_base)
+		return -ENOENT;
+
+	ret = of_property_read_u32(dev->device_node, "clock-frequency", &rate);
+	if (ret) {
+		clk = clk_get(dev, NULL);
+		if (IS_ERR(clk))
+			return PTR_ERR(clk);
+
+		ret = clk_enable(clk);
+		if (ret)
+			return ret;
+
+		rate = clk_get_rate(clk);
+		if (!rate)
+			return -EINVAL;
+	}
+
+	writel_relaxed(SYSTICK_LOAD_RELOAD_MASK, systick_base + SYST_RVR);
+
+	cal = readl(&systick_base + SYST_CALIB);
+	if (cal & SYSTICK_CAL_NOREF)
+		writel(SYSTICK_CTRL_EN | SYSTICK_CTRL_CPU_CLK, systick_base + SYST_CSR);
+	else
+		writel(SYSTICK_CTRL_EN, systick_base + SYST_CSR);
+
+	cs.mult = clocksource_hz2mult(rate, cs.shift);
+
+	return init_clock(&cs);
+}
+
+static struct of_device_id armv7m_systick_dt_ids[] = {
+	{ .compatible = "arm,armv7m-systick", },
+	{ }
+};
+
+static struct driver_d armv7m_systick_driver = {
+	.name = "armv7m-systick-timer",
+	.probe = armv7m_systick_probe,
+	.of_compatible = DRV_OF_COMPAT(armv7m_systick_dt_ids),
+};
+postcore_platform_driver(armv7m_systick_driver);
-- 
2.30.2


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[PATCH 2/2] clocksource: add STM32 Timer driver

[Ahmad Fatoum]

The STM32 timer is 32-bit and thus takes longer to wrap around than the
24-bit SysTick timer. Add a driver for it at a higher priority.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/clocksource/Kconfig       |   4 +
 drivers/clocksource/Makefile      |   1 +
 drivers/clocksource/timer-stm32.c | 122 ++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+)
 create mode 100644 drivers/clocksource/timer-stm32.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 9fae1f2d352e..e1bff23320de 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -120,4 +120,8 @@ config ARMV7M_SYSTICK
 	help
 	  This option enables support for the ARMv7M system timer unit.
 
+config CLKSRC_STM32
+	bool "Clocksource for STM32 SoCs"
+	depends on OFDEVICE && (ARCH_STM32 || COMPILE_TEST)
+
 endmenu
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index a4a7b84fae0c..eceaa990d43d 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -25,3 +25,4 @@ obj-$(CONFIG_CLOCKSOURCE_TI_32K) += timer-ti-32k.o
 obj-$(CONFIG_CLINT_TIMER) += timer-clint.o
 obj-$(CONFIG_RISCV_TIMER) += timer-riscv.o
 obj-$(CONFIG_ARMV7M_SYSTICK) += armv7m_systick.o
+obj-$(CONFIG_CLKSRC_STM32) += timer-stm32.o
diff --git a/drivers/clocksource/timer-stm32.c b/drivers/clocksource/timer-stm32.c
new file mode 100644
index 000000000000..dec48fccf5a2
--- /dev/null
+++ b/drivers/clocksource/timer-stm32.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018, STMicroelectronics - All Rights Reserved
+ * Author(s): Patrice Chotard, <patrice.chotard@foss.st.com> for STMicroelectronics.
+ */
+
+#include <common.h>
+#include <linux/clk.h>
+#include <clock.h>
+#include <init.h>
+#include <io.h>
+
+/* Timer control1 register  */
+#define CR1_CEN			BIT(0)
+#define CR1_ARPE		BIT(7)
+
+/* Event Generation Register register  */
+#define EGR_UG			BIT(0)
+
+/* Auto reload register for free running config */
+#define GPT_FREE_RUNNING	0xFFFFFFFF
+
+#define MHZ_1			1000000
+
+struct stm32_timer_regs {
+	u32 cr1;
+	u32 cr2;
+	u32 smcr;
+	u32 dier;
+	u32 sr;
+	u32 egr;
+	u32 ccmr1;
+	u32 ccmr2;
+	u32 ccer;
+	u32 cnt;
+	u32 psc;
+	u32 arr;
+	u32 reserved;
+	u32 ccr1;
+	u32 ccr2;
+	u32 ccr3;
+	u32 ccr4;
+	u32 reserved1;
+	u32 dcr;
+	u32 dmar;
+	u32 tim2_5_or;
+};
+
+static struct stm32_timer_regs *timer_base;
+
+static u64 stm32_timer_read(void)
+{
+	return readl(&timer_base->cnt);
+}
+
+/* A bit obvious isn't it? */
+static struct clocksource cs = {
+	.read = stm32_timer_read,
+	.mask	= CLOCKSOURCE_MASK(32),
+	.shift = 0,
+	.priority = 100,
+};
+
+static int stm32_timer_probe(struct device_d *dev)
+{
+	struct resource *iores;
+	struct clk *clk;
+	u32 rate, psc;
+	int ret;
+
+	iores = dev_request_mem_resource(dev, 0);
+	if (IS_ERR(iores))
+		return PTR_ERR(iores);
+
+	timer_base = IOMEM(iores->start);
+
+	clk = clk_get(dev, NULL);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	ret = clk_enable(clk);
+	if (ret)
+		return ret;
+
+	/* Stop the timer */
+	clrbits_le32(&timer_base->cr1, CR1_CEN);
+
+	/* get timer clock */
+	rate = clk_get_rate(clk);
+
+	/* we set timer prescaler to obtain a 1MHz timer counter frequency */
+	psc = (rate / MHZ_1) - 1;
+	writel(psc, &timer_base->psc);
+
+	/* Configure timer for auto-reload */
+	setbits_le32(&timer_base->cr1, CR1_ARPE);
+
+	/* load value for auto reload */
+	writel(GPT_FREE_RUNNING, &timer_base->arr);
+
+	/* start timer */
+	setbits_le32(&timer_base->cr1, CR1_CEN);
+
+	/* Update generation */
+	setbits_le32(&timer_base->egr, EGR_UG);
+
+	cs.mult = clocksource_hz2mult(MHZ_1, cs.shift);
+
+	return init_clock(&cs);
+}
+
+static struct of_device_id stm32_timer_dt_ids[] = {
+	{ .compatible = "st,stm32-timer" },
+	{ /* sentinel */ }
+};
+
+static struct driver_d stm32_timer_driver = {
+	.name = "stm32-timer",
+	.probe = stm32_timer_probe,
+	.of_compatible = stm32_timer_dt_ids,
+};
+postcore_platform_driver(stm32_timer_driver);
-- 
2.30.2


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Re: [PATCH 1/2] clocksource: add ARMv7-M SysTick driver

[Sascha Hauer]

On Mon, Jan 31, 2022 at 09:11:45AM +0100, Ahmad Fatoum wrote:
> The SysTick is a simple 24-bit system timer that's required for ARMv7-M
> implementations. Add a clocksource driver for it for Cortex-M system
> support.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  drivers/clocksource/Kconfig          |  5 ++
>  drivers/clocksource/Makefile         |  1 +
>  drivers/clocksource/armv7m_systick.c | 87 ++++++++++++++++++++++++++++
>  3 files changed, 93 insertions(+)
>  create mode 100644 drivers/clocksource/armv7m_systick.c

Applied, thanks

Sascha

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