Patch "misc: ioc4: simplify wave period measurement in clock_calibrate" has been added to the 3.18-stable tree

Patch "misc: ioc4: simplify wave period measurement in clock_calibrate" has been added to the 3.18-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    misc: ioc4: simplify wave period measurement in clock_calibrate

to the 3.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     misc-ioc4-simplify-wave-period-measurement-in-clock_calibrate.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 769105aa740dc0428f2585ec99c457d30aaab364 Mon Sep 17 00:00:00 2001
From: Richard Leitner <dev@g0hl1n.net>
Date: Mon, 8 Dec 2014 16:28:10 +0100
Subject: misc: ioc4: simplify wave period measurement in clock_calibrate
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From: Richard Leitner <dev@g0hl1n.net>

commit 769105aa740dc0428f2585ec99c457d30aaab364 upstream.

The loop for measuring the square wave periods over some cycles is
refactored to be more easily readable. This includes avoiding a
"by-hand-implemented" for loop with a "real" one and adding some
comments.

Furthermore the following compiler warning is avoided by this patch:
drivers/misc/ioc4.c: In function ‘ioc4_probe’:
drivers/misc/ioc4.c:194:16: warning: ‘start’ may be used uninitialized
in this function [-Wmaybe-uninitialized]
  period = (end - start) /
                ^
drivers/misc/ioc4.c:148:11: note: ‘start’ was declared here
  uint64_t start, end, period;
           ^

Signed-off-by: Richard Leitner <dev@g0hl1n.net>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/misc/ioc4.c |   31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

--- a/drivers/misc/ioc4.c
+++ b/drivers/misc/ioc4.c
@@ -144,9 +144,9 @@ ioc4_clock_calibrate(struct ioc4_driver_
 {
 	union ioc4_int_out int_out;
 	union ioc4_gpcr gpcr;
-	unsigned int state, last_state = 1;
+	unsigned int state, last_state;
 	uint64_t start, end, period;
-	unsigned int count = 0;
+	unsigned int count;
 
 	/* Enable output */
 	gpcr.raw = 0;
@@ -167,19 +167,20 @@ ioc4_clock_calibrate(struct ioc4_driver_
 	mmiowb();
 
 	/* Check square wave period averaged over some number of cycles */
-	do {
-		int_out.raw = readl(&idd->idd_misc_regs->int_out.raw);
-		state = int_out.fields.int_out;
-		if (!last_state && state) {
-			count++;
-			if (count == IOC4_CALIBRATE_END) {
-				end = ktime_get_ns();
-				break;
-			} else if (count == IOC4_CALIBRATE_DISCARD)
-				start = ktime_get_ns();
-		}
-		last_state = state;
-	} while (1);
+	start = ktime_get_ns();
+	state = 1; /* make sure the first read isn't a rising edge */
+	for (count = 0; count <= IOC4_CALIBRATE_END; count++) {
+		do { /* wait for a rising edge */
+			last_state = state;
+			int_out.raw = readl(&idd->idd_misc_regs->int_out.raw);
+			state = int_out.fields.int_out;
+		} while (last_state || !state);
+
+		/* discard the first few cycles */
+		if (count == IOC4_CALIBRATE_DISCARD)
+			start = ktime_get_ns();
+	}
+	end = ktime_get_ns();
 
 	/* Calculation rearranged to preserve intermediate precision.
 	 * Logically:


Patches currently in stable-queue which might be from dev@g0hl1n.net are

queue-3.18/misc-ioc4-simplify-wave-period-measurement-in-clock_calibrate.patch