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Commit 4958ebb3 authored by Maxime Coquelin's avatar Maxime Coquelin Committed by Daniel Lezcano
Browse files

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: default avatarChanwoo Choi <cw00.choi@samsung.com>
Acked-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: default avatarMaxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
parent 571fc8e8

drivers/clocksource/Kconfig

+7 −0
Original line number Diff line number Diff line
@@ -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

drivers/clocksource/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

drivers/clocksource/armv7m_systick.c

0 → 100644
+79 −0
Original line number Diff line number Diff line 
/*

 * 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);