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authorRichard Leitner <dev@g0hl1n.net>2014-12-08 16:28:10 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-01-12 05:04:11 -0800
commit769105aa740dc0428f2585ec99c457d30aaab364 (patch)
treea161eda1d8d09afc40537a59071a71334d89f744 /drivers/misc/ioc4.c
parent0ec0cf19201da36af858a6bc052a13e88866f341 (diff)
downloadlinux-769105aa740dc0428f2585ec99c457d30aaab364.tar.bz2
misc: ioc4: simplify wave period measurement in clock_calibrate
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>
Diffstat (limited to 'drivers/misc/ioc4.c')
-rw-r--r--drivers/misc/ioc4.c31
1 files changed, 16 insertions, 15 deletions
diff --git a/drivers/misc/ioc4.c b/drivers/misc/ioc4.c
index 3336ddca45ac..8758d033db23 100644
--- a/drivers/misc/ioc4.c
+++ b/drivers/misc/ioc4.c
@@ -144,9 +144,9 @@ ioc4_clock_calibrate(struct ioc4_driver_data *idd)
{
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_data *idd)
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: