@@ -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);
}
}
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(-)