diff options
Diffstat (limited to 'arch/m68k/coldfire/dma_timer.c')
-rw-r--r-- | arch/m68k/coldfire/dma_timer.c | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/arch/m68k/coldfire/dma_timer.c b/arch/m68k/coldfire/dma_timer.c new file mode 100644 index 000000000000..235ad57c4707 --- /dev/null +++ b/arch/m68k/coldfire/dma_timer.c @@ -0,0 +1,81 @@ +/* + * dma_timer.c -- Freescale ColdFire DMA Timer. + * + * Copyright (C) 2007, Benedikt Spranger <b.spranger@linutronix.de> + * Copyright (C) 2008. Sebastian Siewior, Linutronix + * + */ + +#include <linux/clocksource.h> +#include <linux/io.h> + +#include <asm/machdep.h> +#include <asm/coldfire.h> +#include <asm/mcfpit.h> +#include <asm/mcfsim.h> + +#define DMA_TIMER_0 (0x00) +#define DMA_TIMER_1 (0x40) +#define DMA_TIMER_2 (0x80) +#define DMA_TIMER_3 (0xc0) + +#define DTMR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x400) +#define DTXMR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x402) +#define DTER0 (MCF_IPSBAR + DMA_TIMER_0 + 0x403) +#define DTRR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x404) +#define DTCR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x408) +#define DTCN0 (MCF_IPSBAR + DMA_TIMER_0 + 0x40c) + +#define DMA_FREQ ((MCF_CLK / 2) / 16) + +/* DTMR */ +#define DMA_DTMR_RESTART (1 << 3) +#define DMA_DTMR_CLK_DIV_1 (1 << 1) +#define DMA_DTMR_CLK_DIV_16 (2 << 1) +#define DMA_DTMR_ENABLE (1 << 0) + +static cycle_t cf_dt_get_cycles(struct clocksource *cs) +{ + return __raw_readl(DTCN0); +} + +static struct clocksource clocksource_cf_dt = { + .name = "coldfire_dma_timer", + .rating = 200, + .read = cf_dt_get_cycles, + .mask = CLOCKSOURCE_MASK(32), + .flags = CLOCK_SOURCE_IS_CONTINUOUS, +}; + +static int __init init_cf_dt_clocksource(void) +{ + /* + * We setup DMA timer 0 in free run mode. This incrementing counter is + * used as a highly precious clock source. With MCF_CLOCK = 150 MHz we + * get a ~213 ns resolution and the 32bit register will overflow almost + * every 15 minutes. + */ + __raw_writeb(0x00, DTXMR0); + __raw_writeb(0x00, DTER0); + __raw_writel(0x00000000, DTRR0); + __raw_writew(DMA_DTMR_CLK_DIV_16 | DMA_DTMR_ENABLE, DTMR0); + return clocksource_register_hz(&clocksource_cf_dt, DMA_FREQ); +} + +arch_initcall(init_cf_dt_clocksource); + +#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ +#define CYC2NS_SCALE ((1000000 << CYC2NS_SCALE_FACTOR) / (DMA_FREQ / 1000)) + +static unsigned long long cycles2ns(unsigned long cycl) +{ + return (unsigned long long) ((unsigned long long)cycl * + CYC2NS_SCALE) >> CYC2NS_SCALE_FACTOR; +} + +unsigned long long sched_clock(void) +{ + unsigned long cycl = __raw_readl(DTCN0); + + return cycles2ns(cycl); +} |