All,
Inspired by Stephen Hemminger's "boot time parameter to turn of TSC
usage" patch, I implemented my own version that is a tad bit more
flexible.
With this patch, one can manually specify on the boot cmdline which time
source should be used (if available) for calculating gettimeofday().
This will override the default probed selection. Should the requested
time-source not be available, the code defaults to using the PIT (and
prints a warning saying so).
Please let me know if you have any comments or suggestions.
thanks
-john
diff -Nru a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
--- a/Documentation/kernel-parameters.txt Wed Mar 19 14:50:33 2003
+++ b/Documentation/kernel-parameters.txt Wed Mar 19 14:50:33 2003
@@ -207,6 +207,12 @@
chandev= [HW,NET] Generic channel device initialisation
+ clock= [BUGS=IA-32, HW] gettimeofday timesource override.
+ Forces specified timesource (if avaliable) to be used
+ when calculating gettimeofday(). If specicified timesource
+ is not avalible, it defaults to PIT.
+ Format: { pit | tsc | cyclone | ... }
+
cm206= [HW,CD]
Format: { auto | [<io>,][<irq>] }
diff -Nru a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
--- a/arch/i386/kernel/smpboot.c Wed Mar 19 14:50:33 2003
+++ b/arch/i386/kernel/smpboot.c Wed Mar 19 14:50:33 2003
@@ -422,7 +422,7 @@
/*
* Synchronize the TSC with the BP
*/
- if (cpu_has_tsc)
+ if (cpu_has_tsc && cpu_khz)
synchronize_tsc_ap();
}
@@ -1114,7 +1114,7 @@
/*
* Synchronize the TSC with the AP
*/
- if (cpu_has_tsc && cpucount)
+ if (cpu_has_tsc && cpucount && cpu_khz)
synchronize_tsc_bp();
}
diff -Nru a/arch/i386/kernel/timers/timer.c b/arch/i386/kernel/timers/timer.c
--- a/arch/i386/kernel/timers/timer.c Wed Mar 19 14:50:33 2003
+++ b/arch/i386/kernel/timers/timer.c Wed Mar 19 14:50:33 2003
@@ -1,4 +1,6 @@
+#include <linux/init.h>
#include <linux/kernel.h>
+#include <linux/string.h>
#include <asm/timer.h>
/* list of externed timers */
@@ -17,6 +19,17 @@
NULL,
};
+static char clock_override[10];
+
+static int clock_setup(char* str)
+{
+ if(str){
+ strncpy(clock_override, str,10);
+ str[9] = '\0';
+ }
+ return 1;
+}
+__setup("clock=", clock_setup);
/* iterates through the list of timers, returning the first
* one that initializes successfully.
@@ -28,7 +41,7 @@
/* find most preferred working timer */
while (timers[i]) {
if (timers[i]->init)
- if (timers[i]->init() == 0)
+ if (timers[i]->init(clock_override) == 0)
return timers[i];
++i;
}
diff -Nru a/arch/i386/kernel/timers/timer_cyclone.c b/arch/i386/kernel/timers/timer_cyclone.c
--- a/arch/i386/kernel/timers/timer_cyclone.c Wed Mar 19 14:50:33 2003
+++ b/arch/i386/kernel/timers/timer_cyclone.c Wed Mar 19 14:50:33 2003
@@ -10,6 +10,7 @@
#include <linux/init.h>
#include <linux/timex.h>
#include <linux/errno.h>
+#include <linux/string.h>
#include <asm/timer.h>
#include <asm/io.h>
@@ -73,7 +74,7 @@
return delay_at_last_interrupt + offset;
}
-static int init_cyclone(void)
+static int init_cyclone(char* override)
{
u32* reg;
u32 base; /* saved cyclone base address */
@@ -81,8 +82,11 @@
u32 offset; /* offset from pageaddr to cyclone_timer register */
int i;
+ /* check clock override */
+ if(override[0] && strncmp(override,"cyclone",7))
+ return -ENODEV;
+
/*make sure we're on a summit box*/
- /*XXX need to use proper summit hooks! such as xapic -john*/
if(!use_cyclone) return -ENODEV;
printk(KERN_INFO "Summit chipset: Starting Cyclone Counter.\n");
diff -Nru a/arch/i386/kernel/timers/timer_none.c b/arch/i386/kernel/timers/timer_none.c
--- a/arch/i386/kernel/timers/timer_none.c Wed Mar 19 14:50:33 2003
+++ b/arch/i386/kernel/timers/timer_none.c Wed Mar 19 14:50:33 2003
@@ -1,6 +1,6 @@
#include <asm/timer.h>
-static int init_none(void)
+static int init_none(char* override)
{
return 0;
}
diff -Nru a/arch/i386/kernel/timers/timer_pit.c b/arch/i386/kernel/timers/timer_pit.c
--- a/arch/i386/kernel/timers/timer_pit.c Wed Mar 19 14:50:33 2003
+++ b/arch/i386/kernel/timers/timer_pit.c Wed Mar 19 14:50:33 2003
@@ -17,8 +17,12 @@
extern spinlock_t i8253_lock;
#include "do_timer.h"
-static int init_pit(void)
+static int init_pit(char* override)
{
+ /* check clock override */
+ if(override[0] && strncmp(override,"pit",3)){
+ printk(KERN_ERR "Warning: clock= override failed. Defaulting to PIT\n");
+ }
return 0;
}
diff -Nru a/arch/i386/kernel/timers/timer_tsc.c b/arch/i386/kernel/timers/timer_tsc.c
--- a/arch/i386/kernel/timers/timer_tsc.c Wed Mar 19 14:50:33 2003
+++ b/arch/i386/kernel/timers/timer_tsc.c Wed Mar 19 14:50:33 2003
@@ -8,6 +8,7 @@
#include <linux/timex.h>
#include <linux/errno.h>
#include <linux/cpufreq.h>
+#include <linux/string.h>
#include <asm/timer.h>
#include <asm/io.h>
@@ -242,8 +243,13 @@
#endif
-static int init_tsc(void)
+static int init_tsc(char* override)
{
+
+ /*check clock override*/
+ if(override[0] && strncmp(override,"tsc",3))
+ return -ENODEV;
+
/*
* If we have APM enabled or the CPU clock speed is variable
* (CPU stops clock on HLT or slows clock to save power)
diff -Nru a/include/asm-i386/timer.h b/include/asm-i386/timer.h
--- a/include/asm-i386/timer.h Wed Mar 19 14:50:33 2003
+++ b/include/asm-i386/timer.h Wed Mar 19 14:50:33 2003
@@ -11,7 +11,7 @@
* last timer intruupt.
*/
struct timer_opts{
- int (*init)(void);
+ int (*init)(char*);
void (*mark_offset)(void);
unsigned long (*get_offset)(void);
void (*delay)(unsigned long);
-
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