This patch adds clocksource support for ARMv7-M's System timer, also known as SysTick.
Signed-off-by: Maxime Coquelin <mcoquelin.st...@gmail.com> --- drivers/clocksource/Kconfig | 7 ++++ drivers/clocksource/Makefile | 1 + drivers/clocksource/armv7m_systick.c | 78 ++++++++++++++++++++++++++++++++++++ 3 files changed, 86 insertions(+) create mode 100644 drivers/clocksource/armv7m_systick.c diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig index fc01ec2..fb6011e 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 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 94d90b2..eeea736 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_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 index 0000000..23d8249 --- /dev/null +++ b/drivers/clocksource/armv7m_systick.c @@ -0,0 +1,78 @@ +/* + * Copyright (C) Maxime Coquelin 2015 + * Author: Maxime Coquelin <mcoquelin.st...@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; + void __iomem *base; + u32 rate = 0; + 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)) { + ret = clk_prepare_enable(clk); + if (ret) { + clk_put(clk); + goto out_unmap; + } + + rate = clk_get_rate(clk); + } + + /* If no clock found, try to get clock-frequency property */ + if (!rate) { + ret = of_property_read_u32(np, "clock-frequency", &rate); + if (ret) + goto out_unmap; + } + + 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: + if (!IS_ERR(clk)) + clk_disable_unprepare(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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/