Module Name: src
Committed By: jmcneill
Date: Sat Oct 19 12:34:10 UTC 2024
Modified Files:
src/sys/arch/evbppc/wii: machdep.c
src/sys/arch/powerpc/powerpc: clock.c
Log Message:
Improve delay() accuracy on Nintendo Wii.
The PowerPC delay() implementation converts the timebase frequency to
a number of nanoseconds per tick and uses that value to compute the
delay interval. On the Wii's Broadway processor with a timebase
frequency of 60.75 MHz, some precision is lost as each tick is
approximately 16.46 nanoseconds. The end result is that we sleep for
approximately 2.875% longer than necessary. This also has an impact
on CPU speed calculation on Broadway, which incorrectly reports itself
as 750MHz instead of 729MHz (2.875% faster).
Fix this by introducing an (optional) ticks_per_msec variable that can
be set by the platform and allows delay() to improve the accuracy of
longer delays.
Measured CPU frequency before this change:
[ 1.000000] cpu0: 750.00 MHz, 256KB WB with ECC L2 cache
Measured CPU frequency after this change:
[ 1.000000] cpu0: 729.00 MHz, 256KB WB with ECC L2 cache
To generate a diff of this commit:
cvs rdiff -u -r1.7 -r1.8 src/sys/arch/evbppc/wii/machdep.c
cvs rdiff -u -r1.18 -r1.19 src/sys/arch/powerpc/powerpc/clock.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/evbppc/wii/machdep.c
diff -u src/sys/arch/evbppc/wii/machdep.c:1.7 src/sys/arch/evbppc/wii/machdep.c:1.8
--- src/sys/arch/evbppc/wii/machdep.c:1.7 Sun Oct 13 16:21:37 2024
+++ src/sys/arch/evbppc/wii/machdep.c Sat Oct 19 12:34:10 2024
@@ -1,4 +1,4 @@
-/* $NetBSD: machdep.c,v 1.7 2024/10/13 16:21:37 jmcneill Exp $ */
+/* $NetBSD: machdep.c,v 1.8 2024/10/19 12:34:10 jmcneill Exp $ */
/*
* Copyright (c) 2002, 2024 The NetBSD Foundation, Inc.
@@ -63,7 +63,7 @@
#define _POWERPC_BUS_DMA_PRIVATE
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.7 2024/10/13 16:21:37 jmcneill Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.8 2024/10/19 12:34:10 jmcneill Exp $");
#include "opt_compat_netbsd.h"
#include "opt_ddb.h"
@@ -231,7 +231,8 @@ static void init_decrementer(void);
void
initppc(u_int startkernel, u_int endkernel, u_int args, void *btinfo)
{
- extern u_long ticks_per_sec;
+ extern uint32_t ticks_per_sec;
+ extern uint32_t ticks_per_msec;
extern unsigned char edata[], end[];
extern struct wii_argv wii_argv;
uint32_t mem2_start, mem2_end;
@@ -319,6 +320,7 @@ initppc(u_int startkernel, u_int endkern
* Get CPU clock
*/
ticks_per_sec = TIMEBASE_FREQ_HZ;
+ ticks_per_msec = ticks_per_sec / 1000;
cpu_timebase = ticks_per_sec;
wii_setup();
@@ -441,7 +443,7 @@ init_decrementer(void)
{
extern uint32_t ns_per_tick;
extern uint32_t ticks_per_intr;
- extern u_long ticks_per_sec;
+ extern uint32_t ticks_per_sec;
int scratch, msr;
KASSERT(ticks_per_sec != 0);
Index: src/sys/arch/powerpc/powerpc/clock.c
diff -u src/sys/arch/powerpc/powerpc/clock.c:1.18 src/sys/arch/powerpc/powerpc/clock.c:1.19
--- src/sys/arch/powerpc/powerpc/clock.c:1.18 Sat Jan 20 20:49:11 2024
+++ src/sys/arch/powerpc/powerpc/clock.c Sat Oct 19 12:34:09 2024
@@ -1,4 +1,4 @@
-/* $NetBSD: clock.c,v 1.18 2024/01/20 20:49:11 jmcneill Exp $ */
+/* $NetBSD: clock.c,v 1.19 2024/10/19 12:34:09 jmcneill Exp $ */
/* $OpenBSD: clock.c,v 1.3 1997/10/13 13:42:53 pefo Exp $ */
/*
@@ -33,7 +33,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: clock.c,v 1.18 2024/01/20 20:49:11 jmcneill Exp $");
+__KERNEL_RCSID(0, "$NetBSD: clock.c,v 1.19 2024/10/19 12:34:09 jmcneill Exp $");
#ifdef _KERNEL_OPT
#include "opt_ppcarch.h"
@@ -67,6 +67,7 @@ static u_int get_601_timecount(struct ti
#endif
uint32_t ticks_per_sec;
+uint32_t ticks_per_msec;
uint32_t ns_per_tick;
uint32_t ticks_per_intr = 0;
@@ -232,6 +233,10 @@ delay(unsigned int n)
#endif /* !_ARCH_PPC64 */
{
tb = mftb();
+ if (ticks_per_msec != 0 && n >= 1000) {
+ tb += (n / 1000ULL) * ticks_per_msec;
+ n = n % 1000;
+ }
tb += (n * 1000ULL + ns_per_tick - 1) / ns_per_tick;
#ifdef _ARCH_PPC64
__asm volatile ("1: mftb %0; cmpld %0,%1; blt 1b;"
