83 lines
2.2 KiB
C
83 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* dma_timer.c -- Freescale ColdFire DMA Timer.
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*
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* Copyright (C) 2007, Benedikt Spranger <b.spranger@linutronix.de>
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* Copyright (C) 2008. Sebastian Siewior, Linutronix
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*
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*/
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#include <linux/clocksource.h>
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#include <linux/io.h>
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#include <asm/machdep.h>
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#include <asm/coldfire.h>
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#include <asm/mcfpit.h>
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#include <asm/mcfsim.h>
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#define DMA_TIMER_0 (0x00)
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#define DMA_TIMER_1 (0x40)
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#define DMA_TIMER_2 (0x80)
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#define DMA_TIMER_3 (0xc0)
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#define DTMR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x400)
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#define DTXMR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x402)
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#define DTER0 (MCF_IPSBAR + DMA_TIMER_0 + 0x403)
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#define DTRR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x404)
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#define DTCR0 (MCF_IPSBAR + DMA_TIMER_0 + 0x408)
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#define DTCN0 (MCF_IPSBAR + DMA_TIMER_0 + 0x40c)
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#define DMA_FREQ ((MCF_CLK / 2) / 16)
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/* DTMR */
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#define DMA_DTMR_RESTART (1 << 3)
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#define DMA_DTMR_CLK_DIV_1 (1 << 1)
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#define DMA_DTMR_CLK_DIV_16 (2 << 1)
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#define DMA_DTMR_ENABLE (1 << 0)
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static u64 cf_dt_get_cycles(struct clocksource *cs)
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{
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return __raw_readl(DTCN0);
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}
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static struct clocksource clocksource_cf_dt = {
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.name = "coldfire_dma_timer",
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.rating = 200,
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.read = cf_dt_get_cycles,
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.mask = CLOCKSOURCE_MASK(32),
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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};
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static int __init init_cf_dt_clocksource(void)
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{
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/*
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* We setup DMA timer 0 in free run mode. This incrementing counter is
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* used as a highly precious clock source. With MCF_CLOCK = 150 MHz we
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* get a ~213 ns resolution and the 32bit register will overflow almost
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* every 15 minutes.
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*/
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__raw_writeb(0x00, DTXMR0);
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__raw_writeb(0x00, DTER0);
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__raw_writel(0x00000000, DTRR0);
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__raw_writew(DMA_DTMR_CLK_DIV_16 | DMA_DTMR_ENABLE, DTMR0);
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return clocksource_register_hz(&clocksource_cf_dt, DMA_FREQ);
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}
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arch_initcall(init_cf_dt_clocksource);
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#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
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#define CYC2NS_SCALE ((1000000 << CYC2NS_SCALE_FACTOR) / (DMA_FREQ / 1000))
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static unsigned long long cycles2ns(unsigned long cycl)
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{
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return (unsigned long long) ((unsigned long long)cycl *
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CYC2NS_SCALE) >> CYC2NS_SCALE_FACTOR;
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}
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unsigned long long sched_clock(void)
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{
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unsigned long cycl = __raw_readl(DTCN0);
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return cycles2ns(cycl);
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}
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