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 u64 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 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 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 76 unsigned long long sched_clock(void) 77 { 78 unsigned long cycl = __raw_readl(DTCN0); 79 80 return cycles2ns(cycl); 81 } 82