Unverified Commit 86b8bff7 authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Mark Brown
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spi: Convert to use predefined time multipliers 



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: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210510131120.49253-1-andriy.shevchenko@linux.intel.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent d6e58e37

drivers/spi/spi.c

+28 −13
Original line number Diff line number Diff line
@@ -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);

	}

}