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| author | Richard Leitner <dev@g0hl1n.net> | 2014-12-08 16:28:10 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-01-12 05:04:11 -0800 |
| commit | 769105aa740dc0428f2585ec99c457d30aaab364 (patch) | |
| tree | a161eda1d8d09afc40537a59071a71334d89f744 /drivers/misc/ioc4.c | |
| parent | 0ec0cf19201da36af858a6bc052a13e88866f341 (diff) | |
| download | lwn-769105aa740dc0428f2585ec99c457d30aaab364.tar.gz lwn-769105aa740dc0428f2585ec99c457d30aaab364.zip | |
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.c | 31 |
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: |