1 files changed, 79 insertions, 0 deletions

diff --git a/init/calibrate.c b/init/calibrate.c
new file mode 100644
index 000000000000..c698e04a3dbe
--- /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);
+        }
+
+}