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| author | Richard Leitner <dev@g0hl1n.net> | 2014-12-08 16:28:10 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-04-30 05:49:16 +0200 |
| commit | b0d69335ca0b3f8c68aea40c532b598c673c4890 (patch) | |
| tree | 4400d8439c116c1e3b3ca757d21aa125837de046 /drivers/misc | |
| parent | db65717e7d005b32a6d03858720844c39bcef0d2 (diff) | |
| download | linux-stable-b0d69335ca0b3f8c68aea40c532b598c673c4890.tar.gz linux-stable-b0d69335ca0b3f8c68aea40c532b598c673c4890.tar.bz2 linux-stable-b0d69335ca0b3f8c68aea40c532b598c673c4890.zip | |
misc: ioc4: simplify wave period measurement in clock_calibrate
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>
Diffstat (limited to 'drivers/misc')
| -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: |