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path: root/drivers/clocksource/armv7m_systick.c
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Diffstat (limited to 'drivers/clocksource/armv7m_systick.c')
-rw-r--r--drivers/clocksource/armv7m_systick.c86
1 files changed, 86 insertions, 0 deletions
diff --git a/drivers/clocksource/armv7m_systick.c b/drivers/clocksource/armv7m_systick.c
new file mode 100644
index 0000000000..7e78074480
--- /dev/null
+++ b/drivers/clocksource/armv7m_systick.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) Maxime Coquelin 2015
+ * Author: Maxime Coquelin <mcoquelin.stm32@gmail.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/io.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 int __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 -ENXIO;
+ }
+
+ ret = of_property_read_u32(np, "clock-frequency", &rate);
+ if (ret) {
+ clk = of_clk_get(np, 0);
+ if (IS_ERR(clk)) {
+ ret = PTR_ERR(clk);
+ goto out_unmap;
+ }
+
+ ret = clk_prepare_enable(clk);
+ if (ret)
+ goto out_clk_put;
+
+ rate = clk_get_rate(clk);
+ if (!rate) {
+ ret = -EINVAL;
+ 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 0;
+
+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);
+
+ return ret;
+}
+
+TIMER_OF_DECLARE(arm_systick, "arm,armv7m-systick",
+ system_timer_of_register);