diff options
Diffstat (limited to 'arch/mips/sgi-ip22/ip22-time.c')
| -rw-r--r-- | arch/mips/sgi-ip22/ip22-time.c | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/arch/mips/sgi-ip22/ip22-time.c b/arch/mips/sgi-ip22/ip22-time.c new file mode 100644 index 000000000..045aa89f2 --- /dev/null +++ b/arch/mips/sgi-ip22/ip22-time.c @@ -0,0 +1,131 @@ +/* + * 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_irq_this_cpu(irq); + printk(KERN_ALERT "Oops, got 8254 interrupt.\n"); + ArcRead(0, &c, 1, &cnt); + ArcEnterInteractiveMode(); + irq_exit(); +} |