131 lines
3.5 KiB
C
131 lines
3.5 KiB
C
/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Time operations for IP22 machines. Original code may come from
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* Ralf Baechle or David S. Miller (sorry guys, i'm really not sure)
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*
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* Copyright (C) 2001 by Ladislav Michl
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* Copyright (C) 2003, 06 Ralf Baechle (ralf@linux-mips.org)
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*/
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#include <linux/bcd.h>
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#include <linux/init.h>
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#include <linux/irq.h>
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#include <linux/kernel.h>
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#include <linux/interrupt.h>
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#include <linux/kernel_stat.h>
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#include <linux/time.h>
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#include <asm/cpu.h>
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#include <asm/mipsregs.h>
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#include <asm/i8253.h>
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#include <asm/io.h>
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#include <asm/irq.h>
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#include <asm/time.h>
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#include <asm/sgialib.h>
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#include <asm/sgi/ioc.h>
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#include <asm/sgi/hpc3.h>
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#include <asm/sgi/ip22.h>
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static unsigned long dosample(void)
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{
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u32 ct0, ct1;
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u8 msb, lsb;
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/* Start the counter. */
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sgint->tcword = (SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL |
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SGINT_TCWORD_MRGEN);
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sgint->tcnt2 = SGINT_TCSAMP_COUNTER & 0xff;
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sgint->tcnt2 = SGINT_TCSAMP_COUNTER >> 8;
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/* Get initial counter invariant */
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ct0 = read_c0_count();
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/* Latch and spin until top byte of counter2 is zero */
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do {
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writeb(SGINT_TCWORD_CNT2 | SGINT_TCWORD_CLAT, &sgint->tcword);
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lsb = readb(&sgint->tcnt2);
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msb = readb(&sgint->tcnt2);
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ct1 = read_c0_count();
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} while (msb);
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/* Stop the counter. */
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writeb(SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL | SGINT_TCWORD_MSWST,
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&sgint->tcword);
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/*
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* Return the difference, this is how far the r4k counter increments
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* for every 1/HZ seconds. We round off the nearest 1 MHz of master
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* clock (= 1000000 / HZ / 2).
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*/
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return (ct1 - ct0) / (500000/HZ) * (500000/HZ);
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}
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/*
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* Here we need to calibrate the cycle counter to at least be close.
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*/
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__init void plat_time_init(void)
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{
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unsigned long r4k_ticks[3];
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unsigned long r4k_tick;
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/*
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* Figure out the r4k offset, the algorithm is very simple and works in
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* _all_ cases as long as the 8254 counter register itself works ok (as
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* an interrupt driving timer it does not because of bug, this is why
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* we are using the onchip r4k counter/compare register to serve this
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* purpose, but for r4k_offset calculation it will work ok for us).
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* There are other very complicated ways of performing this calculation
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* but this one works just fine so I am not going to futz around. ;-)
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*/
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printk(KERN_INFO "Calibrating system timer... ");
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dosample(); /* Prime cache. */
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dosample(); /* Prime cache. */
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/* Zero is NOT an option. */
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do {
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r4k_ticks[0] = dosample();
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} while (!r4k_ticks[0]);
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do {
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r4k_ticks[1] = dosample();
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} while (!r4k_ticks[1]);
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if (r4k_ticks[0] != r4k_ticks[1]) {
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printk("warning: timer counts differ, retrying... ");
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r4k_ticks[2] = dosample();
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if (r4k_ticks[2] == r4k_ticks[0]
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|| r4k_ticks[2] == r4k_ticks[1])
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r4k_tick = r4k_ticks[2];
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else {
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printk("disagreement, using average... ");
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r4k_tick = (r4k_ticks[0] + r4k_ticks[1]
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+ r4k_ticks[2]) / 3;
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}
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} else
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r4k_tick = r4k_ticks[0];
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printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick,
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(int) (r4k_tick / (500000 / HZ)),
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(int) (r4k_tick % (500000 / HZ)));
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mips_hpt_frequency = r4k_tick * HZ;
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if (ip22_is_fullhouse())
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setup_pit_timer();
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}
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/* Generic SGI handler for (spurious) 8254 interrupts */
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void indy_8254timer_irq(void)
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{
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int irq = SGI_8254_0_IRQ;
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ULONG cnt;
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char c;
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irq_enter();
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kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));
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printk(KERN_ALERT "Oops, got 8254 interrupt.\n");
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ArcRead(0, &c, 1, &cnt);
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ArcEnterInteractiveMode();
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irq_exit();
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}
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