2 * Moschip MCS814x timer routines
4 * Copyright (C) 2012, Florian Fainelli <florian@openwrt.org>
8 #include <linux/kernel.h>
9 #include <linux/interrupt.h>
10 #include <linux/time.h>
11 #include <linux/timex.h>
12 #include <linux/irq.h>
13 #include <linux/err.h>
14 #include <linux/clk.h>
17 #include <linux/of_address.h>
19 #include <asm/mach/time.h>
20 #include <mach/mcs814x.h>
22 /* Timer block registers */
23 #define TIMER_VAL 0x00
24 #define TIMER_CTL 0x04
25 #define TIMER_CTL_EN 0x01
26 #define TIMER_CTL_DBG 0x02
28 static u32 last_reload;
29 static u32 timer_correct;
30 static u32 clock_rate;
31 static u32 timer_reload_value;
32 static void __iomem *mcs814x_timer_base;
34 static inline u32 ticks2usecs(u32 x)
36 return x / (clock_rate / 1000000);
40 * Returns number of ms since last clock interrupt. Note that interrupts
41 * will have been disabled by do_gettimeoffset()
43 static u32 mcs814x_gettimeoffset(void)
45 u32 ticks = readl_relaxed(mcs814x_timer_base + TIMER_VAL);
47 if (ticks < last_reload)
48 return ticks2usecs(ticks + (u32)(0xffffffff - last_reload));
50 return ticks2usecs(ticks - last_reload);
54 static irqreturn_t mcs814x_timer_interrupt(int irq, void *dev_id)
56 u32 count = readl_relaxed(mcs814x_timer_base + TIMER_VAL);
58 /* take into account delay up to this moment */
59 last_reload = count + timer_correct + timer_reload_value;
61 if (last_reload < timer_reload_value) {
62 last_reload = timer_reload_value;
64 if (timer_correct == 0)
65 timer_correct = readl_relaxed(mcs814x_timer_base + TIMER_VAL) - count;
67 writel_relaxed(last_reload, mcs814x_timer_base + TIMER_VAL);
74 static struct irqaction mcs814x_timer_irq = {
75 .name = "mcs814x-timer",
76 .flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
77 .handler = mcs814x_timer_interrupt,
80 static struct of_device_id mcs814x_timer_ids[] = {
81 { .compatible = "moschip,mcs814x-timer" },
85 static void __init mcs814x_of_timer_init(void)
87 struct device_node *np;
88 const unsigned int *intspec;
90 np = of_find_matching_node(NULL, mcs814x_timer_ids);
92 panic("unable to find compatible timer node in dtb");
94 mcs814x_timer_base = of_iomap(np, 0);
95 if (!mcs814x_timer_base)
96 panic("unable to remap timer cpu registers");
98 intspec = of_get_property(np, "interrupts", NULL);
100 panic("no interrupts property for timer");
102 mcs814x_timer_irq.irq = be32_to_cpup(intspec);
105 void __init mcs814x_timer_init(void)
109 arch_gettimeoffset = mcs814x_gettimeoffset;
111 clk = clk_get_sys("timer0", NULL);
112 if (IS_ERR_OR_NULL(clk))
113 panic("unable to get timer0 clock");
115 clock_rate = clk_get_rate(clk);
117 mcs814x_of_timer_init();
119 pr_info("Timer frequency: %d (kHz)\n", clock_rate / 1000);
121 timer_reload_value = 0xffffffff - (clock_rate / HZ);
124 writel_relaxed(~TIMER_CTL_EN, mcs814x_timer_base + TIMER_CTL);
125 writel_relaxed(timer_reload_value, mcs814x_timer_base + TIMER_VAL);
126 last_reload = timer_reload_value;
128 setup_irq(mcs814x_timer_irq.irq, &mcs814x_timer_irq);
129 /* enable timer, stop timer in debug mode */
130 writel_relaxed(TIMER_CTL_EN | TIMER_CTL_DBG,
131 mcs814x_timer_base + TIMER_CTL);