clocksource/drivers/armv7m_systick: Add ARM System timer driver

This patch adds clocksource support for ARMv7-M's System timer,
also known as SysTick.

Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 47f9f22..2c67ca9 100644 (file)
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -144,6 +144,13 @@ config CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
        help
         Use ARM global timer clock source as sched_clock
 
+config ARMV7M_SYSTICK
+       bool
+       select CLKSRC_OF if OF
+       select CLKSRC_MMIO
+       help
+         This options enables support for the ARMv7M 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 5928e35..ebfb5dc 100644 (file)
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -46,6 +46,7 @@ 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-$(CONFIG_ARMV7M_SYSTICK)           += armv7m_systick.o
 obj-$(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/armv7m_systick.c b/drivers/clocksource/armv7m_systick.c
new file mode 100644 (file)
index 0000000..addfd2c
--- /dev/null
+++ b/drivers/clocksource/armv7m_systick.c
@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) Maxime Coquelin 2015
+ * Author:  Maxime Coquelin <mcoquelin.stm32@gmail.com>
+ * 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 = NULL;
+       void __iomem *base;
+       u32 rate;
+       int ret;
+
+       base = of_iomap(np, 0);
+       if (!base) {
+               pr_warn("system-timer: invalid base address\n");
+               return;
+       }
+
+       ret = of_property_read_u32(np, "clock-frequency", &rate);
+       if (ret) {
+               clk = of_clk_get(np, 0);
+               if (IS_ERR(clk))
+                       goto out_unmap;
+
+               ret = clk_prepare_enable(clk);
+               if (ret)
+                       goto out_clk_put;
+
+               rate = clk_get_rate(clk);
+               if (!rate)
+                       goto out_clk_disable;
+       }
+
+       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);
+               if (clk)
+                       goto out_clk_disable;
+               else
+                       goto out_unmap;
+       }
+
+       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);
+       pr_warn("ARM System timer register failed (%d)\n", ret);
+}
+
+CLOCKSOURCE_OF_DECLARE(arm_systick, "arm,armv7m-systick",
+                       system_timer_of_register);