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// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <linux/i8253.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/smp.h>
#include <linux/time.h>
#include <linux/clockchips.h>
#include <asm/sni.h>
#include <asm/time.h>
#define SNI_CLOCK_TICK_RATE 3686400
#define SNI_COUNTER2_DIV 64
#define SNI_COUNTER0_DIV ((SNI_CLOCK_TICK_RATE / SNI_COUNTER2_DIV) / HZ)
static int a20r_set_periodic(struct clock_event_device *evt)
{
*(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0x34;
wmb();
*(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV;
wmb();
*(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV >> 8;
wmb();
*(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0xb4;
wmb();
*(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV;
wmb();
*(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV >> 8;
wmb();
return 0;
}
static struct clock_event_device a20r_clockevent_device = {
.name = "a20r-timer",
.features = CLOCK_EVT_FEAT_PERIODIC,
/* .mult, .shift, .max_delta_ns and .min_delta_ns left uninitialized */
.rating = 300,
.irq = SNI_A20R_IRQ_TIMER,
.set_state_periodic = a20r_set_periodic,
};
static irqreturn_t a20r_interrupt(int irq, void *dev_id)
{
struct clock_event_device *cd = dev_id;
*(volatile u8 *)A20R_PT_TIM0_ACK = 0;
wmb();
cd->event_handler(cd);
return IRQ_HANDLED;
}
/*
* a20r platform uses 2 counters to divide the input frequency.
* Counter 2 output is connected to Counter 0 & 1 input.
*/
static void __init sni_a20r_timer_setup(void)
{
struct clock_event_device *cd = &a20r_clockevent_device;
unsigned int cpu = smp_processor_id();
cd->cpumask = cpumask_of(cpu);
clockevents_register_device(cd);
if (request_irq(SNI_A20R_IRQ_TIMER, a20r_interrupt,
IRQF_PERCPU | IRQF_TIMER, "a20r-timer", cd))
pr_err("Failed to register a20r-timer interrupt\n");
}
#define SNI_8254_TICK_RATE 1193182UL
#define SNI_8254_TCSAMP_COUNTER ((SNI_8254_TICK_RATE / HZ) + 255)
static __init unsigned long dosample(void)
{
u32 ct0, ct1;
volatile u8 msb;
/* Start the counter. */
outb_p(0x34, 0x43);
outb_p(SNI_8254_TCSAMP_COUNTER & 0xff, 0x40);
outb(SNI_8254_TCSAMP_COUNTER >> 8, 0x40);
/* Get initial counter invariant */
ct0 = read_c0_count();
/* Latch and spin until top byte of counter0 is zero */
do {
outb(0x00, 0x43);
(void) inb(0x40);
msb = inb(0x40);
ct1 = read_c0_count();
} while (msb);
/* Stop the counter. */
outb(0x38, 0x43);
/*
* Return the difference, this is how far the r4k counter increments
* for every 1/HZ seconds. We round off the nearest 1 MHz of master
* clock (= 1000000 / HZ / 2).
*/
/*return (ct1 - ct0 + (500000/HZ/2)) / (500000/HZ) * (500000/HZ);*/
return (ct1 - ct0) / (500000/HZ) * (500000/HZ);
}
/*
* Here we need to calibrate the cycle counter to at least be close.
*/
void __init plat_time_init(void)
{
unsigned long r4k_ticks[3];
unsigned long r4k_tick;
/*
* Figure out the r4k offset, the algorithm is very simple and works in
* _all_ cases as long as the 8254 counter register itself works ok (as
* an interrupt driving timer it does not because of bug, this is why
* we are using the onchip r4k counter/compare register to serve this
* purpose, but for r4k_offset calculation it will work ok for us).
* There are other very complicated ways of performing this calculation
* but this one works just fine so I am not going to futz around. ;-)
*/
printk(KERN_INFO "Calibrating system timer... ");
dosample(); /* Prime cache. */
dosample(); /* Prime cache. */
/* Zero is NOT an option. */
do {
r4k_ticks[0] = dosample();
} while (!r4k_ticks[0]);
do {
r4k_ticks[1] = dosample();
} while (!r4k_ticks[1]);
if (r4k_ticks[0] != r4k_ticks[1]) {
printk("warning: timer counts differ, retrying... ");
r4k_ticks[2] = dosample();
if (r4k_ticks[2] == r4k_ticks[0]
|| r4k_ticks[2] == r4k_ticks[1])
r4k_tick = r4k_ticks[2];
else {
printk("disagreement, using average... ");
r4k_tick = (r4k_ticks[0] + r4k_ticks[1]
+ r4k_ticks[2]) / 3;
}
} else
r4k_tick = r4k_ticks[0];
printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick,
(int) (r4k_tick / (500000 / HZ)),
(int) (r4k_tick % (500000 / HZ)));
mips_hpt_frequency = r4k_tick * HZ;
switch (sni_brd_type) {
case SNI_BRD_10:
case SNI_BRD_10NEW:
case SNI_BRD_TOWER_OASIC:
case SNI_BRD_MINITOWER:
sni_a20r_timer_setup();
break;
}
setup_pit_timer();
}
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