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
37static cycle_t cf_dt_get_cycles(struct clocksource *cs)
38{
39	return __raw_readl(DTCN0);
40}
41
42static 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	.shift		= 20,
48	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
49};
50
51static int __init  init_cf_dt_clocksource(void)
52{
53	/*
54	 * We setup DMA timer 0 in free run mode. This incrementing counter is
55	 * used as a highly precious clock source. With MCF_CLOCK = 150 MHz we
56	 * get a ~213 ns resolution and the 32bit register will overflow almost
57	 * every 15 minutes.
58	 */
59	__raw_writeb(0x00, DTXMR0);
60	__raw_writeb(0x00, DTER0);
61	__raw_writel(0x00000000, DTRR0);
62	__raw_writew(DMA_DTMR_CLK_DIV_16 | DMA_DTMR_ENABLE, DTMR0);
63	clocksource_cf_dt.mult = clocksource_hz2mult(DMA_FREQ,
64						     clocksource_cf_dt.shift);
65	return clocksource_register(&clocksource_cf_dt);
66}
67
68arch_initcall(init_cf_dt_clocksource);
69
70#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
71#define CYC2NS_SCALE	((1000000 << CYC2NS_SCALE_FACTOR) / (DMA_FREQ / 1000))
72
73static unsigned long long cycles2ns(unsigned long cycl)
74{
75	return (unsigned long long) ((unsigned long long)cycl *
76			CYC2NS_SCALE) >> CYC2NS_SCALE_FACTOR;
77}
78
79unsigned long long sched_clock(void)
80{
81	unsigned long cycl = __raw_readl(DTCN0);
82
83	return cycles2ns(cycl);
84}