arch/m68k/coldfire/dma_timer.c

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