ip22-time.c
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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Time operations for IP22 machines. Original code may come from
* Ralf Baechle or David S. Miller (sorry guys, i'm really not sure)
*
* Copyright (C) 2001 by Ladislav Michl
* Copyright (C) 2003, 06 Ralf Baechle (ralf@linux-mips.org)
*/
#include <linux/bcd.h>
#include <linux/i8253.h>
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/time.h>
#include <linux/ftrace.h>
#include <asm/cpu.h>
#include <asm/mipsregs.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/time.h>
#include <asm/sgialib.h>
#include <asm/sgi/ioc.h>
#include <asm/sgi/hpc3.h>
#include <asm/sgi/ip22.h>
static unsigned long dosample(void)
{
u32 ct0, ct1;
u8 msb;
/* Start the counter. */
sgint->tcword = (SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL |
SGINT_TCWORD_MRGEN);
sgint->tcnt2 = SGINT_TCSAMP_COUNTER & 0xff;
sgint->tcnt2 = SGINT_TCSAMP_COUNTER >> 8;
/* Get initial counter invariant */
ct0 = read_c0_count();
/* Latch and spin until top byte of counter2 is zero */
do {
writeb(SGINT_TCWORD_CNT2 | SGINT_TCWORD_CLAT, &sgint->tcword);
(void) readb(&sgint->tcnt2);
msb = readb(&sgint->tcnt2);
ct1 = read_c0_count();
} while (msb);
/* Stop the counter. */
writeb(SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL | SGINT_TCWORD_MSWST,
&sgint->tcword);
/*
* 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) * (500000/HZ);
}
/*
* Here we need to calibrate the cycle counter to at least be close.
*/
__init void 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;
if (ip22_is_fullhouse())
setup_pit_timer();
}
/* Generic SGI handler for (spurious) 8254 interrupts */
void __irq_entry indy_8254timer_irq(void)
{
int irq = SGI_8254_0_IRQ;
ULONG cnt;
char c;
irq_enter();
kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));
printk(KERN_ALERT "Oops, got 8254 interrupt.\n");
ArcRead(0, &c, 1, &cnt);
ArcEnterInteractiveMode();
irq_exit();
}