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spi: Convert to use predefined time multipliers

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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>
Link: https://lore.kernel.org/r/20210510131120.49253-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Andy Shevchenko 2021-05-10 16:11:20 +03:00 committed by Mark Brown
parent d6e58e3796
commit 86b8bff7e3
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GPG Key ID: 24D68B725D5487D0
1 changed files with 28 additions and 13 deletions
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41
drivers/spi/spi.c
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@ -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);
}
}