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@xxxxxxxxxxxxxxx> know about it.
>From 769105aa740dc0428f2585ec99c457d30aaab364 Mon Sep 17 00:00:00 2001
From: Richard Leitner <dev@xxxxxxxxxx>
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@xxxxxxxxxx>
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@xxxxxxxxxx>
Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxx are
queue-3.18/misc-ioc4-simplify-wave-period-measurement-in-clock_calibrate.patch