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-rw-r--r--init/calibrate.c79
1 files changed, 79 insertions, 0 deletions
diff --git a/init/calibrate.c b/init/calibrate.c
new file mode 100644
index 00000000000..c698e04a3db
--- /dev/null
+++ b/init/calibrate.c
@@ -0,0 +1,79 @@
+/* calibrate.c: default delay calibration
+ *
+ * Excised from init/main.c
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ */
+
+#include <linux/sched.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+
+static unsigned long preset_lpj;
+static int __init lpj_setup(char *str)
+{
+ preset_lpj = simple_strtoul(str,NULL,0);
+ return 1;
+}
+
+__setup("lpj=", lpj_setup);
+
+/*
+ * This is the number of bits of precision for the loops_per_jiffy. Each
+ * bit takes on average 1.5/HZ seconds. This (like the original) is a little
+ * better than 1%
+ */
+#define LPS_PREC 8
+
+void __devinit calibrate_delay(void)
+{
+ unsigned long ticks, loopbit;
+ int lps_precision = LPS_PREC;
+
+ if (preset_lpj) {
+ loops_per_jiffy = preset_lpj;
+ printk("Calibrating delay loop (skipped)... "
+ "%lu.%02lu BogoMIPS preset\n",
+ loops_per_jiffy/(500000/HZ),
+ (loops_per_jiffy/(5000/HZ)) % 100);
+ } else {
+ loops_per_jiffy = (1<<12);
+
+ printk(KERN_DEBUG "Calibrating delay loop... ");
+ while ((loops_per_jiffy <<= 1) != 0) {
+ /* wait for "start of" clock tick */
+ ticks = jiffies;
+ while (ticks == jiffies)
+ /* nothing */;
+ /* Go .. */
+ ticks = jiffies;
+ __delay(loops_per_jiffy);
+ ticks = jiffies - ticks;
+ if (ticks)
+ break;
+ }
+
+ /*
+ * Do a binary approximation to get loops_per_jiffy set to
+ * equal one clock (up to lps_precision bits)
+ */
+ loops_per_jiffy >>= 1;
+ loopbit = loops_per_jiffy;
+ while (lps_precision-- && (loopbit >>= 1)) {
+ loops_per_jiffy |= loopbit;
+ ticks = jiffies;
+ while (ticks == jiffies)
+ /* nothing */;
+ ticks = jiffies;
+ __delay(loops_per_jiffy);
+ if (jiffies != ticks) /* longer than 1 tick */
+ loops_per_jiffy &= ~loopbit;
+ }
+
+ /* Round the value and print it */
+ printk("%lu.%02lu BogoMIPS (lpj=%lu)\n",
+ loops_per_jiffy/(500000/HZ),
+ (loops_per_jiffy/(5000/HZ)) % 100,
+ loops_per_jiffy);
+ }
+
+}