mirror of https://gitee.com/openkylin/linux.git
148 lines
3.7 KiB
C
148 lines
3.7 KiB
C
/*
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* linux/arch/arm/mach-nomadik/timer.c
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*
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* Copyright (C) 2008 STMicroelectronics
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* Copyright (C) 2009 Alessandro Rubini, somewhat based on at91sam926x
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2, as
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* published by the Free Software Foundation.
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*/
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/irq.h>
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#include <linux/io.h>
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#include <linux/clockchips.h>
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#include <linux/jiffies.h>
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#include <asm/mach/time.h>
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#include <plat/mtu.h>
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static u32 nmdk_count; /* accumulated count */
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static u32 nmdk_cycle; /* write-once */
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/* setup by the platform code */
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void __iomem *mtu_base;
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/*
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* clocksource: the MTU device is a decrementing counters, so we negate
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* the value being read.
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*/
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static cycle_t nmdk_read_timer(struct clocksource *cs)
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{
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u32 count = readl(mtu_base + MTU_VAL(0));
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return nmdk_count + nmdk_cycle - count;
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}
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static struct clocksource nmdk_clksrc = {
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.name = "mtu_0",
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.rating = 120,
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.read = nmdk_read_timer,
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.shift = 20,
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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};
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/*
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* Clockevent device: currently only periodic mode is supported
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*/
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static void nmdk_clkevt_mode(enum clock_event_mode mode,
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struct clock_event_device *dev)
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{
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unsigned long flags;
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switch (mode) {
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case CLOCK_EVT_MODE_PERIODIC:
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/* enable interrupts -- and count current value? */
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raw_local_irq_save(flags);
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writel(readl(mtu_base + MTU_IMSC) | 1, mtu_base + MTU_IMSC);
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raw_local_irq_restore(flags);
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break;
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case CLOCK_EVT_MODE_ONESHOT:
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BUG(); /* Not supported, yet */
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/* FALLTHROUGH */
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case CLOCK_EVT_MODE_SHUTDOWN:
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case CLOCK_EVT_MODE_UNUSED:
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/* disable irq */
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raw_local_irq_save(flags);
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writel(readl(mtu_base + MTU_IMSC) & ~1, mtu_base + MTU_IMSC);
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raw_local_irq_restore(flags);
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break;
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case CLOCK_EVT_MODE_RESUME:
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break;
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}
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}
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static struct clock_event_device nmdk_clkevt = {
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.name = "mtu_0",
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.features = CLOCK_EVT_FEAT_PERIODIC,
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.shift = 32,
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.rating = 100,
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.set_mode = nmdk_clkevt_mode,
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};
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/*
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* IRQ Handler for the timer 0 of the MTU block. The irq is not shared
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* as we are the only users of mtu0 by now.
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*/
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static irqreturn_t nmdk_timer_interrupt(int irq, void *dev_id)
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{
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/* ack: "interrupt clear register" */
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writel(1 << 0, mtu_base + MTU_ICR);
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/* we can't count lost ticks, unfortunately */
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nmdk_count += nmdk_cycle;
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nmdk_clkevt.event_handler(&nmdk_clkevt);
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return IRQ_HANDLED;
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}
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/*
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* Set up timer interrupt, and return the current time in seconds.
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*/
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static struct irqaction nmdk_timer_irq = {
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.name = "Nomadik Timer Tick",
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.flags = IRQF_DISABLED | IRQF_TIMER,
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.handler = nmdk_timer_interrupt,
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};
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static void nmdk_timer_reset(void)
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{
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u32 cr;
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writel(0, mtu_base + MTU_CR(0)); /* off */
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/* configure load and background-load, and fire it up */
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writel(nmdk_cycle, mtu_base + MTU_LR(0));
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writel(nmdk_cycle, mtu_base + MTU_BGLR(0));
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cr = MTU_CRn_PERIODIC | MTU_CRn_PRESCALE_1 | MTU_CRn_32BITS;
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writel(cr, mtu_base + MTU_CR(0));
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writel(cr | MTU_CRn_ENA, mtu_base + MTU_CR(0));
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}
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void __init nmdk_timer_init(void)
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{
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unsigned long rate;
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int bits;
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rate = CLOCK_TICK_RATE; /* 2.4MHz */
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nmdk_cycle = (rate + HZ/2) / HZ;
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/* Init the timer and register clocksource */
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nmdk_timer_reset();
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nmdk_clksrc.mult = clocksource_hz2mult(rate, nmdk_clksrc.shift);
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bits = 8*sizeof(nmdk_count);
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nmdk_clksrc.mask = CLOCKSOURCE_MASK(bits);
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if (clocksource_register(&nmdk_clksrc))
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printk(KERN_ERR "timer: failed to initialize clock "
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"source %s\n", nmdk_clksrc.name);
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/* Register irq and clockevents */
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setup_irq(IRQ_MTU0, &nmdk_timer_irq);
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nmdk_clkevt.mult = div_sc(rate, NSEC_PER_SEC, nmdk_clkevt.shift);
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nmdk_clkevt.cpumask = cpumask_of(0);
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clockevents_register_device(&nmdk_clkevt);
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}
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