155 lines
3.9 KiB
C
155 lines
3.9 KiB
C
/*
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* OpenRISC time.c
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*
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* Linux architectural port borrowing liberally from similar works of
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* others. All original copyrights apply as per the original source
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* declaration.
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*
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* Modifications for the OpenRISC architecture:
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* Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/time.h>
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#include <linux/timex.h>
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#include <linux/interrupt.h>
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#include <linux/ftrace.h>
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#include <linux/clocksource.h>
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#include <linux/clockchips.h>
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#include <linux/irq.h>
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#include <linux/io.h>
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#include <asm/cpuinfo.h>
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static int openrisc_timer_set_next_event(unsigned long delta,
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struct clock_event_device *dev)
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{
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u32 c;
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/* Read 32-bit counter value, add delta, mask off the low 28 bits.
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* We're guaranteed delta won't be bigger than 28 bits because the
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* generic timekeeping code ensures that for us.
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*/
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c = mfspr(SPR_TTCR);
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c += delta;
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c &= SPR_TTMR_TP;
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/* Set counter and enable interrupt.
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* Keep timer in continuous mode always.
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*/
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mtspr(SPR_TTMR, SPR_TTMR_CR | SPR_TTMR_IE | c);
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return 0;
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}
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/* This is the clock event device based on the OR1K tick timer.
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* As the timer is being used as a continuous clock-source (required for HR
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* timers) we cannot enable the PERIODIC feature. The tick timer can run using
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* one-shot events, so no problem.
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*/
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static struct clock_event_device clockevent_openrisc_timer = {
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.name = "openrisc_timer_clockevent",
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.features = CLOCK_EVT_FEAT_ONESHOT,
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.rating = 300,
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.set_next_event = openrisc_timer_set_next_event,
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};
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static inline void timer_ack(void)
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{
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/* Clear the IP bit and disable further interrupts */
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/* This can be done very simply... we just need to keep the timer
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running, so just maintain the CR bits while clearing the rest
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of the register
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*/
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mtspr(SPR_TTMR, SPR_TTMR_CR);
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}
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/*
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* The timer interrupt is mostly handled in generic code nowadays... this
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* function just acknowledges the interrupt and fires the event handler that
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* has been set on the clockevent device by the generic time management code.
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*
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* This function needs to be called by the timer exception handler and that's
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* all the exception handler needs to do.
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*/
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irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs)
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{
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struct pt_regs *old_regs = set_irq_regs(regs);
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struct clock_event_device *evt = &clockevent_openrisc_timer;
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timer_ack();
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/*
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* update_process_times() expects us to have called irq_enter().
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*/
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irq_enter();
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evt->event_handler(evt);
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irq_exit();
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set_irq_regs(old_regs);
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return IRQ_HANDLED;
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}
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static __init void openrisc_clockevent_init(void)
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{
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clockevent_openrisc_timer.cpumask = cpumask_of(0);
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/* We only have 28 bits */
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clockevents_config_and_register(&clockevent_openrisc_timer,
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cpuinfo.clock_frequency,
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100, 0x0fffffff);
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}
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/**
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* Clocksource: Based on OpenRISC timer/counter
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*
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* This sets up the OpenRISC Tick Timer as a clock source. The tick timer
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* is 32 bits wide and runs at the CPU clock frequency.
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*/
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static cycle_t openrisc_timer_read(struct clocksource *cs)
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{
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return (cycle_t) mfspr(SPR_TTCR);
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}
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static struct clocksource openrisc_timer = {
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.name = "openrisc_timer",
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.rating = 200,
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.read = openrisc_timer_read,
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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 openrisc_timer_init(void)
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{
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if (clocksource_register_hz(&openrisc_timer, cpuinfo.clock_frequency))
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panic("failed to register clocksource");
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/* Enable the incrementer: 'continuous' mode with interrupt disabled */
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mtspr(SPR_TTMR, SPR_TTMR_CR);
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return 0;
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}
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void __init time_init(void)
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{
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u32 upr;
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upr = mfspr(SPR_UPR);
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if (!(upr & SPR_UPR_TTP))
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panic("Linux not supported on devices without tick timer");
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openrisc_timer_init();
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openrisc_clockevent_init();
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}
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