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authorMaxime Coquelin <mcoquelin.stm32@gmail.com>2015-05-09 09:53:46 +0200
committerDaniel Lezcano <daniel.lezcano@linaro.org>2015-06-02 12:10:14 +0200
commit4958ebb3d027886c46b936453745dba59b09c578 (patch)
tree803c91e5c84850baecf869d77f5152aca2cdd1d1 /drivers/clocksource/armv7m_systick.c
parent571fc8e836a1537b87804358c7baa9882d25b754 (diff)
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>
Diffstat (limited to 'drivers/clocksource/armv7m_systick.c')
-rw-r--r--drivers/clocksource/armv7m_systick.c79
1 files changed, 79 insertions, 0 deletions
diff --git a/drivers/clocksource/armv7m_systick.c b/drivers/clocksource/armv7m_systick.c
new file mode 100644
index 000000000000..addfd2c64f54
--- /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);