We have a lot of hard coded values in nanoseconds or other units. Use predefined constants to make it more clear.
While at it, add or amend comments in the corresponding functions.
Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com --- drivers/spi/spi.c | 41 ++++++++++++++++++++++++++++------------- 1 file changed, 28 insertions(+), 13 deletions(-)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 2350d131871b..9160e9e52aae 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1118,10 +1118,20 @@ static int spi_transfer_wait(struct spi_controller *ctlr, if (!speed_hz) speed_hz = 100000;
- ms = 8LL * 1000LL * xfer->len; + /* + * For each byte we wait for 8 cycles of the SPI clock. + * Since speed is defined in Hz and we want milliseconds, + * use respective multiplier, but before the division, + * otherwise we may get 0 for short transfers. + */ + ms = 8LL * MSEC_PER_SEC * xfer->len; do_div(ms, speed_hz); - ms += ms + 200; /* some tolerance */
+ /* + * Increase it twice and add 200 ms tolerance, use + * predefined maximum in case of overflow. + */ + ms += ms + 200; if (ms > UINT_MAX) ms = UINT_MAX;
@@ -1144,10 +1154,10 @@ static void _spi_transfer_delay_ns(u32 ns) { if (!ns) return; - if (ns <= 1000) { + if (ns <= NSEC_PER_USEC) { ndelay(ns); } else { - u32 us = DIV_ROUND_UP(ns, 1000); + u32 us = DIV_ROUND_UP(ns, NSEC_PER_USEC);
if (us <= 10) udelay(us); @@ -1167,21 +1177,25 @@ int spi_delay_to_ns(struct spi_delay *_delay, struct spi_transfer *xfer)
switch (unit) { case SPI_DELAY_UNIT_USECS: - delay *= 1000; + delay *= NSEC_PER_USEC; break; - case SPI_DELAY_UNIT_NSECS: /* nothing to do here */ + case SPI_DELAY_UNIT_NSECS: + /* Nothing to do here */ break; case SPI_DELAY_UNIT_SCK: /* clock cycles need to be obtained from spi_transfer */ if (!xfer) return -EINVAL; - /* if there is no effective speed know, then approximate - * by underestimating with half the requested hz + /* + * If there is unknown effective speed, approximate it + * by underestimating with half of the requested hz. */ hz = xfer->effective_speed_hz ?: xfer->speed_hz / 2; if (!hz) return -EINVAL; - delay *= DIV_ROUND_UP(1000000000, hz); + + /* Convert delay to nanoseconds */ + delay *= DIV_ROUND_UP(NSEC_PER_SEC, hz); break; default: return -EINVAL; @@ -1213,6 +1227,7 @@ EXPORT_SYMBOL_GPL(spi_delay_exec); static void _spi_transfer_cs_change_delay(struct spi_message *msg, struct spi_transfer *xfer) { + u32 default_delay_ns = 10 * NSEC_PER_USEC; u32 delay = xfer->cs_change_delay.value; u32 unit = xfer->cs_change_delay.unit; int ret; @@ -1220,16 +1235,16 @@ static void _spi_transfer_cs_change_delay(struct spi_message *msg, /* return early on "fast" mode - for everything but USECS */ if (!delay) { if (unit == SPI_DELAY_UNIT_USECS) - _spi_transfer_delay_ns(10000); + _spi_transfer_delay_ns(default_delay_ns); return; }
ret = spi_delay_exec(&xfer->cs_change_delay, xfer); if (ret) { dev_err_once(&msg->spi->dev, - "Use of unsupported delay unit %i, using default of 10us\n", - unit); - _spi_transfer_delay_ns(10000); + "Use of unsupported delay unit %i, using default of %luus\n", + unit, default_delay_ns / NSEC_PER_USEC); + _spi_transfer_delay_ns(default_delay_ns); } }