1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * dma_timer.c -- Freescale ColdFire DMA Timer.
4 *
5 * Copyright (C) 2007, Benedikt Spranger <b.spranger@linutronix.de>
6 * Copyright (C) 2008. Sebastian Siewior, Linutronix
7 *
8 */
9
10 #include <linux/clocksource.h>
11 #include <linux/io.h>
12
13 #include <asm/machdep.h>
14 #include <asm/coldfire.h>
15 #include <asm/mcfpit.h>
16 #include <asm/mcfsim.h>
17
18 #define DMA_TIMER_0 (0x00)
19 #define DMA_TIMER_1 (0x40)
20 #define DMA_TIMER_2 (0x80)
21 #define DMA_TIMER_3 (0xc0)
22
23 #define DTMR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x400)
24 #define DTXMR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x402)
25 #define DTER0 (MCF_IPSBAR + DMA_TIMER_0 + 0x403)
26 #define DTRR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x404)
27 #define DTCR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x408)
28 #define DTCN0 (MCF_IPSBAR + DMA_TIMER_0 + 0x40c)
29
30 #define DMA_FREQ ((MCF_CLK / 2) / 16)
31
32 /* DTMR */
33 #define DMA_DTMR_RESTART (1 << 3)
34 #define DMA_DTMR_CLK_DIV_1 (1 << 1)
35 #define DMA_DTMR_CLK_DIV_16 (2 << 1)
36 #define DMA_DTMR_ENABLE (1 << 0)
37
cf_dt_get_cycles(struct clocksource * cs)38 static u64 cf_dt_get_cycles(struct clocksource *cs)
39 {
40 return __raw_readl(DTCN0);
41 }
42
43 static struct clocksource clocksource_cf_dt = {
44 .name = "coldfire_dma_timer",
45 .rating = 200,
46 .read = cf_dt_get_cycles,
47 .mask = CLOCKSOURCE_MASK(32),
48 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
49 };
50
init_cf_dt_clocksource(void)51 static 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 return clocksource_register_hz(&clocksource_cf_dt, DMA_FREQ);
64 }
65
66 arch_initcall(init_cf_dt_clocksource);
67
68 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
69 #define CYC2NS_SCALE ((1000000 << CYC2NS_SCALE_FACTOR) / (DMA_FREQ / 1000))
70
cycles2ns(unsigned long cycl)71 static unsigned long long cycles2ns(unsigned long cycl)
72 {
73 return (unsigned long long) ((unsigned long long)cycl *
74 CYC2NS_SCALE) >> CYC2NS_SCALE_FACTOR;
75 }
76
sched_clock(void)77 unsigned long long sched_clock(void)
78 {
79 unsigned long cycl = __raw_readl(DTCN0);
80
81 return cycles2ns(cycl);
82 }
83