diff options
| -rw-r--r-- | arch/m68k/mac/via.c | 102 |
1 files changed, 53 insertions, 49 deletions
diff --git a/arch/m68k/mac/via.c b/arch/m68k/mac/via.c index 5c3d650d6a6f..8b8848998751 100644 --- a/arch/m68k/mac/via.c +++ b/arch/m68k/mac/via.c @@ -55,16 +55,6 @@ static __u8 rbv_clear; static int gIER,gIFR,gBufA,gBufB; /* - * Timer defs. - */ - -#define TICK_SIZE 10000 -#define MAC_CLOCK_TICK (783300/HZ) /* ticks per HZ */ -#define MAC_CLOCK_LOW (MAC_CLOCK_TICK&0xFF) -#define MAC_CLOCK_HIGH (MAC_CLOCK_TICK>>8) - - -/* * On Macs with a genuine VIA chip there is no way to mask an individual slot * interrupt. This limitation also seems to apply to VIA clone logic cores in * Quadra-like ASICs. (RBV and OSS machines don't have this limitation.) @@ -272,22 +262,6 @@ void __init via_init(void) } /* - * Start the 100 Hz clock - */ - -void __init via_init_clock(irq_handler_t func) -{ - via1[vACR] |= 0x40; - via1[vT1LL] = MAC_CLOCK_LOW; - via1[vT1LH] = MAC_CLOCK_HIGH; - via1[vT1CL] = MAC_CLOCK_LOW; - via1[vT1CH] = MAC_CLOCK_HIGH; - - if (request_irq(IRQ_MAC_TIMER_1, func, 0, "timer", func)) - pr_err("Couldn't register %s interrupt\n", "timer"); -} - -/* * Debugging dump, used in various places to see what's going on. */ @@ -315,29 +289,6 @@ void via_debug_dump(void) } /* - * This is always executed with interrupts disabled. - * - * TBI: get time offset between scheduling timer ticks - */ - -u32 mac_gettimeoffset(void) -{ - unsigned long ticks, offset = 0; - - /* read VIA1 timer 2 current value */ - ticks = via1[vT1CL] | (via1[vT1CH] << 8); - /* The probability of underflow is less than 2% */ - if (ticks > MAC_CLOCK_TICK - MAC_CLOCK_TICK / 50) - /* Check for pending timer interrupt in VIA1 IFR */ - if (via1[vIFR] & 0x40) offset = TICK_SIZE; - - ticks = MAC_CLOCK_TICK - ticks; - ticks = ticks * 10000L / MAC_CLOCK_TICK; - - return (ticks + offset) * 1000; -} - -/* * Flush the L2 cache on Macs that have it by flipping * the system into 24-bit mode for an instant. */ @@ -622,3 +573,56 @@ int via2_scsi_drq_pending(void) return via2[gIFR] & (1 << IRQ_IDX(IRQ_MAC_SCSIDRQ)); } EXPORT_SYMBOL(via2_scsi_drq_pending); + +/* timer and clock source */ + +#define VIA_CLOCK_FREQ 783360 /* VIA "phase 2" clock in Hz */ +#define VIA_TIMER_INTERVAL (1000000 / HZ) /* microseconds per jiffy */ +#define VIA_TIMER_CYCLES (VIA_CLOCK_FREQ / HZ) /* clock cycles per jiffy */ + +#define VIA_TC (VIA_TIMER_CYCLES - 2) /* including 0 and -1 */ +#define VIA_TC_LOW (VIA_TC & 0xFF) +#define VIA_TC_HIGH (VIA_TC >> 8) + +void __init via_init_clock(irq_handler_t timer_routine) +{ + if (request_irq(IRQ_MAC_TIMER_1, timer_routine, 0, "timer", NULL)) { + pr_err("Couldn't register %s interrupt\n", "timer"); + return; + } + + via1[vT1LL] = VIA_TC_LOW; + via1[vT1LH] = VIA_TC_HIGH; + via1[vT1CL] = VIA_TC_LOW; + via1[vT1CH] = VIA_TC_HIGH; + via1[vACR] |= 0x40; +} + +u32 mac_gettimeoffset(void) +{ + unsigned long flags; + u8 count_high; + u16 count, offset = 0; + + /* + * Timer counter wrap-around is detected with the timer interrupt flag + * but reading the counter low byte (vT1CL) would reset the flag. + * Also, accessing both counter registers is essentially a data race. + * These problems are avoided by ignoring the low byte. Clock accuracy + * is 256 times worse (error can reach 0.327 ms) but CPU overhead is + * reduced by avoiding slow VIA register accesses. + */ + + local_irq_save(flags); + count_high = via1[vT1CH]; + if (count_high == 0xFF) + count_high = 0; + if (count_high > 0 && (via1[vIFR] & VIA_TIMER_1_INT)) + offset = VIA_TIMER_CYCLES; + local_irq_restore(flags); + + count = count_high << 8; + count = VIA_TIMER_CYCLES - count + offset; + + return ((count * VIA_TIMER_INTERVAL) / VIA_TIMER_CYCLES) * 1000; +} |