SAN People | 73a59c1 | 2006-01-09 17:05:41 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * linux/arch/arm/mach-at91rm9200/time.c |
| 3 | * |
| 4 | * Copyright (C) 2003 SAN People |
| 5 | * Copyright (C) 2003 ATMEL |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License as published by |
| 9 | * the Free Software Foundation; either version 2 of the License, or |
| 10 | * (at your option) any later version. |
| 11 | * |
| 12 | * This program is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | * GNU General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License |
| 18 | * along with this program; if not, write to the Free Software |
| 19 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 20 | */ |
| 21 | |
| 22 | #include <linux/config.h> |
| 23 | #include <linux/init.h> |
| 24 | #include <linux/interrupt.h> |
| 25 | #include <linux/kernel.h> |
| 26 | #include <linux/sched.h> |
| 27 | #include <linux/time.h> |
| 28 | |
| 29 | #include <asm/hardware.h> |
| 30 | #include <asm/io.h> |
| 31 | #include <asm/irq.h> |
| 32 | #include <asm/mach/time.h> |
| 33 | |
| 34 | /* |
| 35 | * The ST_CRTR is updated asynchronously to the master clock. It is therefore |
| 36 | * necessary to read it twice (with the same value) to ensure accuracy. |
| 37 | */ |
| 38 | static inline unsigned long read_CRTR(void) { |
| 39 | unsigned long x1, x2; |
| 40 | |
| 41 | do { |
| 42 | x1 = at91_sys_read(AT91_ST_CRTR); |
| 43 | x2 = at91_sys_read(AT91_ST_CRTR); |
| 44 | } while (x1 != x2); |
| 45 | |
| 46 | return x1; |
| 47 | } |
| 48 | |
| 49 | /* |
| 50 | * Returns number of microseconds since last timer interrupt. Note that interrupts |
| 51 | * will have been disabled by do_gettimeofday() |
| 52 | * 'LATCH' is hwclock ticks (see CLOCK_TICK_RATE in timex.h) per jiffy. |
| 53 | * 'tick' is usecs per jiffy (linux/timex.h). |
| 54 | */ |
| 55 | static unsigned long at91rm9200_gettimeoffset(void) |
| 56 | { |
| 57 | unsigned long elapsed; |
| 58 | |
| 59 | elapsed = (read_CRTR() - at91_sys_read(AT91_ST_RTAR)) & AT91_ST_ALMV; |
| 60 | |
| 61 | return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH; |
| 62 | } |
| 63 | |
| 64 | /* |
| 65 | * IRQ handler for the timer. |
| 66 | */ |
| 67 | static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs) |
| 68 | { |
| 69 | unsigned long rtar; |
| 70 | |
| 71 | if (at91_sys_read(AT91_ST_SR) & AT91_ST_PITS) { /* This is a shared interrupt */ |
| 72 | write_seqlock(&xtime_lock); |
| 73 | |
| 74 | do { |
| 75 | timer_tick(regs); |
| 76 | rtar = (at91_sys_read(AT91_ST_RTAR) + LATCH) & AT91_ST_ALMV; |
| 77 | at91_sys_write(AT91_ST_RTAR, rtar); |
| 78 | } while (((read_CRTR() - at91_sys_read(AT91_ST_RTAR)) & AT91_ST_ALMV) >= LATCH); |
| 79 | |
| 80 | write_sequnlock(&xtime_lock); |
| 81 | |
| 82 | return IRQ_HANDLED; |
| 83 | } |
| 84 | else |
| 85 | return IRQ_NONE; /* not handled */ |
| 86 | } |
| 87 | |
| 88 | static struct irqaction at91rm9200_timer_irq = { |
| 89 | .name = "at91_tick", |
| 90 | .flags = SA_SHIRQ | SA_INTERRUPT, |
| 91 | .handler = at91rm9200_timer_interrupt |
| 92 | }; |
| 93 | |
| 94 | /* |
| 95 | * Set up timer interrupt. |
| 96 | */ |
| 97 | void __init at91rm9200_timer_init(void) |
| 98 | { |
| 99 | /* Disable all timer interrupts */ |
| 100 | at91_sys_write(AT91_ST_IDR, AT91_ST_PITS | AT91_ST_WDOVF | AT91_ST_RTTINC | AT91_ST_ALMS); |
| 101 | (void) at91_sys_read(AT91_ST_SR); /* Clear any pending interrupts */ |
| 102 | |
| 103 | /* |
| 104 | * Make IRQs happen for the system timer. |
| 105 | */ |
| 106 | setup_irq(AT91_ID_SYS, &at91rm9200_timer_irq); |
| 107 | |
| 108 | /* Set initial alarm to 0 */ |
| 109 | at91_sys_write(AT91_ST_RTAR, 0); |
| 110 | |
| 111 | /* Real time counter incremented every 30.51758 microseconds */ |
| 112 | at91_sys_write(AT91_ST_RTMR, 1); |
| 113 | |
| 114 | /* Set Period Interval timer */ |
| 115 | at91_sys_write(AT91_ST_PIMR, LATCH); |
| 116 | |
| 117 | /* Change the kernel's 'tick' value to 10009 usec. (the default is 10000) */ |
| 118 | tick_usec = (LATCH * 1000000) / CLOCK_TICK_RATE; |
| 119 | |
| 120 | /* Enable Period Interval Timer interrupt */ |
| 121 | at91_sys_write(AT91_ST_IER, AT91_ST_PITS); |
| 122 | } |
| 123 | |
| 124 | struct sys_timer at91rm9200_timer = { |
| 125 | .init = at91rm9200_timer_init, |
| 126 | .offset = at91rm9200_gettimeoffset, |
| 127 | }; |