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-rw-r--r--init/calibrate.c73
1 files changed, 40 insertions, 33 deletions
diff --git a/init/calibrate.c b/init/calibrate.c
index 24fe022c55f9..b71643a7acae 100644
--- a/init/calibrate.c
+++ b/init/calibrate.c
@@ -119,10 +119,47 @@ static unsigned long __cpuinit calibrate_delay_direct(void) {return 0;}
*/
#define LPS_PREC 8
-void __cpuinit calibrate_delay(void)
+static unsigned long __cpuinit calibrate_delay_converge(void)
{
- unsigned long ticks, loopbit;
+ unsigned long lpj, ticks, loopbit;
int lps_precision = LPS_PREC;
+
+ lpj = (1<<12);
+ while ((lpj <<= 1) != 0) {
+ /* wait for "start of" clock tick */
+ ticks = jiffies;
+ while (ticks == jiffies)
+ /* nothing */;
+ /* Go .. */
+ ticks = jiffies;
+ __delay(lpj);
+ ticks = jiffies - ticks;
+ if (ticks)
+ break;
+ }
+
+ /*
+ * Do a binary approximation to get lpj set to
+ * equal one clock (up to lps_precision bits)
+ */
+ lpj >>= 1;
+ loopbit = lpj;
+ while (lps_precision-- && (loopbit >>= 1)) {
+ lpj |= loopbit;
+ ticks = jiffies;
+ while (ticks == jiffies)
+ /* nothing */;
+ ticks = jiffies;
+ __delay(lpj);
+ if (jiffies != ticks) /* longer than 1 tick */
+ lpj &= ~loopbit;
+ }
+
+ return lpj;
+}
+
+void __cpuinit calibrate_delay(void)
+{
static bool printed;
if (preset_lpj) {
@@ -139,39 +176,9 @@ void __cpuinit calibrate_delay(void)
pr_info("Calibrating delay using timer "
"specific routine.. ");
} else {
- loops_per_jiffy = (1<<12);
-
if (!printed)
pr_info("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;
- }
+ loops_per_jiffy = calibrate_delay_converge();
}
if (!printed)
pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n",