[src/trunk]: src/sys/arch/mac68k/mac68k Write a new low-level assembly help f...

[scottr <scottr%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/90225c91d95e
branches:  trunk
changeset: 473609:90225c91d95e
user:      scottr <scottr%NetBSD.org@localhost>
date:      Wed Jun 09 06:59:53 1999 +0000

description:
Write a new low-level assembly help for delay() and the calibrator.  This
eliminates stalls during instruction prefetch and makes the delay
consistent regardless of kernel configuration.

diffstat:

 sys/arch/mac68k/mac68k/clock.c  |  33 +++++++++++++++------------------
 sys/arch/mac68k/mac68k/locore.s |  29 ++++++++++++++++++++++++++++-
 2 files changed, 43 insertions(+), 19 deletions(-)

diffs (128 lines):

diff -r 2a951a46b4f2 -r 90225c91d95e sys/arch/mac68k/mac68k/clock.c
--- a/sys/arch/mac68k/mac68k/clock.c    Wed Jun 09 05:43:10 1999 +0000
+++ b/sys/arch/mac68k/mac68k/clock.c    Wed Jun 09 06:59:53 1999 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: clock.c,v 1.36 1997/10/07 03:04:55 scottr Exp $        */
+/*     $NetBSD: clock.c,v 1.37 1999/06/09 06:59:53 scottr Exp $        */
 
 /*
  * Copyright (c) 1988 University of Utah.
@@ -100,6 +100,7 @@
 #endif
 
 void   rtclock_intr __P((void));
+int    _delay __P((u_int));
 
 #define        DIFF19041970    2082844800
 #define        DIFF19701990    630720000
@@ -425,45 +426,42 @@
 
 /*
  * delay(usec)
- *     Delay usec microseconds.
+ *     Delay at least usec microseconds.
  *
  * The delay_factor is scaled up by a factor of 128 to avoid loss
- * of precision for small delays.  As a result of this, note that
- * delays larger that LARGE_DELAY will be up to 128 usec too short,
- * due to adjustments for calculations involving 32 bit values.
+ * of precision for small delays.
  */
 void
 delay(usec)
-       unsigned usec;
+       u_int usec;
 {
-       volatile unsigned int cycles;
+       volatile u_int cycles;
 
        if (usec > LARGE_DELAY)
-               cycles = (usec >> 7) * delay_factor;
+               cycles = ((usec + 127) >> 7) * delay_factor;
        else
                cycles = ((usec > 0 ? usec : 1) * delay_factor) >> 7;
 
-       while ((cycles-- > 0) && delay_flag);
+       (void)_delay(cycles);
 }
 
-static unsigned        dummy_delay __P((unsigned));
+static u_int   dummy_delay __P((u_int));
 /*
  * Dummy delay calibration.  Functionally identical to delay(), but
  * returns the number of times through the loop.
  */
-static unsigned
+static u_int
 dummy_delay(usec)
-       unsigned usec;
+       u_int usec;
 {
-       volatile unsigned int cycles;
+       volatile u_int cycles;
 
        if (usec > LARGE_DELAY)
-               cycles = (usec >> 7) * delay_factor;
+               cycles = ((usec + 127) >> 7) * delay_factor;
        else
                cycles = ((usec > 0 ? usec : 1) * delay_factor) >> 7;
 
-       while ((cycles-- > 0) && delay_flag);
-
+       cycles = _delay(cycles);
        return ((delay_factor >> 7) - cycles);
 }
 
@@ -482,8 +480,7 @@
 void
 mac68k_calibrate_delay()
 {
-       int n;
-       unsigned sum;
+       u_int sum, n;
 
        /* Disable VIA1 timer 1 interrupts and set up service routine */
        via_reg(VIA1, vIER) = V1IF_T1;
diff -r 2a951a46b4f2 -r 90225c91d95e sys/arch/mac68k/mac68k/locore.s
--- a/sys/arch/mac68k/mac68k/locore.s   Wed Jun 09 05:43:10 1999 +0000
+++ b/sys/arch/mac68k/mac68k/locore.s   Wed Jun 09 06:59:53 1999 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: locore.s,v 1.114 1999/04/29 16:27:16 christos Exp $    */
+/*     $NetBSD: locore.s,v 1.115 1999/06/09 06:59:53 scottr Exp $      */
 
 /*
  * Copyright (c) 1988 University of Utah.
@@ -1491,6 +1491,33 @@
        rts
 
 /*
+ * Low-level microsecond delay helper
+ *
+ * The branch target for the loops must be aligned on a half-line (8-byte)
+ * boundary to minimize cache effects.  This guarantees both that there
+ * will be no prefetch stalls due to cache line burst operations and that
+ * the loops will run from a single cache half-line.
+ */
+       .align  8                       | align to half-line boundary
+ENTRY(_delay)
+       movl    sp@(4),d0
+       jeq     Ldelayexit
+       movl    d0,d1
+       andl    #0xffff,d0
+       swap    d1
+       subql   #1,d0
+       andl    #0xffff,d1
+Ldelay:
+       tstl    _C_LABEL(delay_flag)
+       dbeq    d0,Ldelay
+       dbeq    d1,Ldelay
+       addql   #1,d0
+       swap    d1
+       orl     d1,d0
+Ldelayexit:
+       rts
+
+/*
  * Handle the nitty-gritty of rebooting the machine.
  * Basically we just turn off the MMU and jump to the appropriate ROM routine.
  * Note that we must be running in an address range that is mapped one-to-one