From 769105aa740dc0428f2585ec99c457d30aaab364 Mon Sep 17 00:00:00 2001 From: Richard Leitner Date: Mon, 8 Dec 2014 16:28:10 +0100 Subject: [PATCH] misc: ioc4: simplify wave period measurement in clock_calibrate MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Acked-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman --- drivers/misc/ioc4.c | 31 ++++++++++++++++--------------- 1 file 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: -- 2.11.0