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5732b38d SS |
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 | ||
37 | static cycle_t cf_dt_get_cycles(void) | |
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 | .shift = 20, | |
48 | .flags = CLOCK_SOURCE_IS_CONTINUOUS, | |
49 | }; | |
50 | ||
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 | clocksource_cf_dt.mult = clocksource_hz2mult(DMA_FREQ, | |
64 | clocksource_cf_dt.shift); | |
65 | return clocksource_register(&clocksource_cf_dt); | |
66 | } | |
67 | ||
68 | arch_initcall(init_cf_dt_clocksource); |