linux-kernel - [PATCH 1/3] calibrate: extract fall-back calculation into own helper

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Date:	Fri, 10 Sep 2010 12:54:26 +0300
From:	Phil Carmody <ext-phil.2.carmody@...ia.com>
To:	mingo@...e.hu, gregkh@...e.de
Cc:	linux-kernel@...r.kernel.org, travis@....com, akataria@...are.com
Subject: [PATCH 1/3] calibrate: extract fall-back calculation into own helper

From: Carmody Phil.2 (EXT-Ixonos/Helsinki) <ext-phil.2.carmody@...ia.com>

So that it can be modified more clinically.

Signed-off-by: Phil Carmody <ext-phil.2.carmody@...ia.com>
---
 init/calibrate.c |   73 +++++++++++++++++++++++++++++------------------------
 1 files changed, 40 insertions(+), 33 deletions(-)

diff --git a/init/calibrate.c b/init/calibrate.c
index 6eb48e5..f7042ff 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",
-- 
1.7.2.rc1.37.gf8c40

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