86 lines
1.8 KiB
C
86 lines
1.8 KiB
C
/*
|
|
* 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/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;
|
|
}
|
|
|
|
CLOCKSOURCE_OF_DECLARE(arm_systick, "arm,armv7m-systick",
|
|
system_timer_of_register);
|