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