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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2012 Regents of the University of California
* Copyright (C) 2017 SiFive
*/
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <asm/sbi.h>
/*
* All RISC-V systems have a timer attached to every hart. These timers can be
* read by the 'rdcycle' pseudo instruction, and can use the SBI to setup
* events. In order to abstract the architecture-specific timer reading and
* setting functions away from the clock event insertion code, we provide
* function pointers to the clockevent subsystem that perform two basic
* operations: rdtime() reads the timer on the current CPU, and
* next_event(delta) sets the next timer event to 'delta' cycles in the future.
* As the timers are inherently a per-cpu resource, these callbacks perform
* operations on the current hart. There is guaranteed to be exactly one timer
* per hart on all RISC-V systems.
*/
static int riscv_clock_next_event(unsigned long delta,
struct clock_event_device *ce)
{
csr_set(sie, SIE_STIE);
sbi_set_timer(get_cycles64() + delta);
return 0;
}
static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
.name = "riscv_timer_clockevent",
.features = CLOCK_EVT_FEAT_ONESHOT,
.rating = 100,
.set_next_event = riscv_clock_next_event,
};
/*
* It is guaranteed that all the timers across all the harts are synchronized
* within one tick of each other, so while this could technically go
* backwards when hopping between CPUs, practically it won't happen.
*/
static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
{
return get_cycles64();
}
static DEFINE_PER_CPU(struct clocksource, riscv_clocksource) = {
.name = "riscv_clocksource",
.rating = 300,
.mask = CLOCKSOURCE_MASK(BITS_PER_LONG),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
.read = riscv_clocksource_rdtime,
};
static int riscv_timer_starting_cpu(unsigned int cpu)
{
struct clock_event_device *ce = per_cpu_ptr(&riscv_clock_event, cpu);
ce->cpumask = cpumask_of(cpu);
clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
csr_set(sie, SIE_STIE);
return 0;
}
static int riscv_timer_dying_cpu(unsigned int cpu)
{
csr_clear(sie, SIE_STIE);
return 0;
}
/* called directly from the low-level interrupt handler */
void riscv_timer_interrupt(void)
{
struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
csr_clear(sie, SIE_STIE);
evdev->event_handler(evdev);
}
static int __init riscv_timer_init_dt(struct device_node *n)
{
int cpu_id = riscv_of_processor_hartid(n), error;
struct clocksource *cs;
if (cpu_id != smp_processor_id())
return 0;
cs = per_cpu_ptr(&riscv_clocksource, cpu_id);
clocksource_register_hz(cs, riscv_timebase);
error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
"clockevents/riscv/timer:starting",
riscv_timer_starting_cpu, riscv_timer_dying_cpu);
if (error)
pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
error, cpu_id);
return error;
}
TIMER_OF_DECLARE(riscv_timer, "riscv", riscv_timer_init_dt);
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