1 /*
2 * dma_timer.c -- Freescale ColdFire DMA Timer.
3 *
4 * Copyright (C) 2007, Benedikt Spranger <b.spranger@linutronix.de>
5 * Copyright (C) 2008. Sebastian Siewior, Linutronix
6 *
7 */
8
9 #include <linux/clocksource.h>
10 #include <linux/io.h>
11
12 #include <asm/machdep.h>
13 #include <asm/coldfire.h>
14 #include <asm/mcfpit.h>
15 #include <asm/mcfsim.h>
16
17 #define DMA_TIMER_0 (0x00)
18 #define DMA_TIMER_1 (0x40)
19 #define DMA_TIMER_2 (0x80)
20 #define DMA_TIMER_3 (0xc0)
21
22 #define DTMR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x400)
23 #define DTXMR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x402)
24 #define DTER0 (MCF_IPSBAR + DMA_TIMER_0 + 0x403)
25 #define DTRR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x404)
26 #define DTCR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x408)
27 #define DTCN0 (MCF_IPSBAR + DMA_TIMER_0 + 0x40c)
28
29 #define DMA_FREQ ((MCF_CLK / 2) / 16)
30
31 /* DTMR */
32 #define DMA_DTMR_RESTART (1 << 3)
33 #define DMA_DTMR_CLK_DIV_1 (1 << 1)
34 #define DMA_DTMR_CLK_DIV_16 (2 << 1)
35 #define DMA_DTMR_ENABLE (1 << 0)
36
cf_dt_get_cycles(struct clocksource * cs)37 static cycle_t cf_dt_get_cycles(struct clocksource *cs)
38 {
39 return __raw_readl(DTCN0);
40 }
41
42 static struct clocksource clocksource_cf_dt = {
43 .name = "coldfire_dma_timer",
44 .rating = 200,
45 .read = cf_dt_get_cycles,
46 .mask = CLOCKSOURCE_MASK(32),
47 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
48 };
49
init_cf_dt_clocksource(void)50 static int __init init_cf_dt_clocksource(void)
51 {
52 /*
53 * We setup DMA timer 0 in free run mode. This incrementing counter is
54 * used as a highly precious clock source. With MCF_CLOCK = 150 MHz we
55 * get a ~213 ns resolution and the 32bit register will overflow almost
56 * every 15 minutes.
57 */
58 __raw_writeb(0x00, DTXMR0);
59 __raw_writeb(0x00, DTER0);
60 __raw_writel(0x00000000, DTRR0);
61 __raw_writew(DMA_DTMR_CLK_DIV_16 | DMA_DTMR_ENABLE, DTMR0);
62 return clocksource_register_hz(&clocksource_cf_dt, DMA_FREQ);
63 }
64
65 arch_initcall(init_cf_dt_clocksource);
66
67 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
68 #define CYC2NS_SCALE ((1000000 << CYC2NS_SCALE_FACTOR) / (DMA_FREQ / 1000))
69
cycles2ns(unsigned long cycl)70 static unsigned long long cycles2ns(unsigned long cycl)
71 {
72 return (unsigned long long) ((unsigned long long)cycl *
73 CYC2NS_SCALE) >> CYC2NS_SCALE_FACTOR;
74 }
75
sched_clock(void)76 unsigned long long sched_clock(void)
77 {
78 unsigned long cycl = __raw_readl(DTCN0);
79
80 return cycles2ns(cycl);
81 }
82