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-rw-r--r--arch/m68k/mac/via.c102
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;
+}