This patch adds clocksource support for ARMv7-M's System timer,
also known as SysTick.
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>
---
.../devicetree/bindings/arm/system_timer.txt | 15 +++++
drivers/clocksource/Kconfig | 7 ++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/arm_system_timer.c | 74 ++++++++++++++++++++++
4 files changed, 97 insertions(+)
create mode 100644 Documentation/devicetree/bindings/arm/system_timer.txt
create mode 100644 drivers/clocksource/arm_system_timer.c
diff --git a/Documentation/devicetree/bindings/arm/system_timer.txt b/Documentation/devicetree/bindings/arm/system_timer.txt
new file mode 100644
index 0000000..35268b7
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/system_timer.txt
@@ -0,0 +1,15 @@
+* ARM System Timer
+
+ARMv7-M includes a system timer, known as SysTick. Current driver only
+implements the clocksource feature.
+
+Required properties:
+- compatible : Should be "arm,armv7m-systick"
+- reg : The address range of the timer
+- clocks : The input clock of the timer
+
+systick: system-timer {
+ compatible = "arm,armv7m-systick";
+ reg = <0xe000e010 0x10>;
+ clocks = <&clk_systick>;
+};
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index fc01ec2..f9fe4ac 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -124,6 +124,13 @@ config CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
help
Use ARM global timer clock source as sched_clock
+config ARM_SYSTEM_TIMER
+ bool
+ select CLKSRC_OF if OF
+ select CLKSRC_MMIO
+ help
+ This options enables support for the ARM system timer unit
+
config ATMEL_PIT
select CLKSRC_OF if OF
def_bool SOC_AT91SAM9 || SOC_SAMA5
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 94d90b2..194400b 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -42,6 +42,7 @@ obj-$(CONFIG_MTK_TIMER) += mtk_timer.o
obj-$(CONFIG_ARM_ARCH_TIMER) += arm_arch_timer.o
obj-$(CONFIG_ARM_GLOBAL_TIMER) += arm_global_timer.o
+obj-$(CONFIG_ARM_SYSTEM_TIMER) += arm_system_timer.o
obj-$(CONFIG_CLKSRC_METAG_GENERIC) += metag_generic.o
obj-$(CONFIG_ARCH_HAS_TICK_BROADCAST) += dummy_timer.o
obj-$(CONFIG_ARCH_KEYSTONE) += timer-keystone.o
diff --git a/drivers/clocksource/arm_system_timer.c b/drivers/clocksource/arm_system_timer.c
new file mode 100644
index 0000000..69e6ef9
--- /dev/null
+++ b/drivers/clocksource/arm_system_timer.c
@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) Maxime Coquelin 2015
+ * Author: Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>
+ * License terms: GNU General Public License (GPL), version 2
+ */
+
+#include <linux/kernel.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/clk.h>
+#include <linux/bitops.h>
+
+#define SYST_CSR 0x00
+#define SYST_RVR 0x04
+#define SYST_CVR 0x08
+#define SYST_CALIB 0x0c
+
+#define SYST_CSR_ENABLE BIT(0)
+
+#define SYSTICK_LOAD_RELOAD_MASK 0x00FFFFFF
+
+static void __init system_timer_of_register(struct device_node *np)
+{
+ struct clk *clk;
+ void __iomem *base;
+ unsigned long rate;
+ int ret;
+
+ base = of_iomap(np, 0);
+ if (!base) {
+ pr_warn("system-timer: invalid base address\n");
+ return;
+ }
+
+ clk = of_clk_get(np, 0);
+ if (IS_ERR(clk)) {
+ pr_warn("system-timer: clk not found\n");
+ ret = PTR_ERR(clk);
+ goto out_unmap;
+ }
+
+ ret = clk_prepare_enable(clk);
+ if (ret)
+ goto out_clk_put;
+
+ rate = clk_get_rate(clk);
+
+ writel_relaxed(SYSTICK_LOAD_RELOAD_MASK, base + SYST_RVR);
+ writel_relaxed(SYST_CSR_ENABLE, base + SYST_CSR);
+
+ ret = clocksource_mmio_init(base + SYST_CVR, "arm_system_timer", rate,
+ 200, 24, clocksource_mmio_readl_down);
+ if (ret) {
+ pr_err("failed to init clocksource (%d)\n", ret);
+ goto out_clk_disable;
+ }
+
+ pr_info("ARM System timer initialized as clocksource\n");
+
+ return;
+
+out_clk_disable:
+ clk_disable_unprepare(clk);
+out_clk_put:
+ clk_put(clk);
+out_unmap:
+ iounmap(base);
+ WARN(ret, "ARM System timer register failed (%d)\n", ret);
+}
+
+CLOCKSOURCE_OF_DECLARE(arm_systick, "arm,armv7m-systick",
+ system_timer_of_register);
--
1.9.1
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