2021-05-10 13:23:22

by Andy Shevchenko

Subject: [PATCH v1 1/1] 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: Andy Shevchenko <[email protected]>
---
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 f9885c096563..407420977a73 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);
}
}

--
2.30.2

2021-05-11 18:24:21

by Mark Brown

Subject: Re: [PATCH v1 1/1] spi: Convert to use predefined time multipliers

On Mon, 10 May 2021 16:11:20 +0300, Andy Shevchenko wrote:
> 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.

Applied to

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: Convert to use predefined time multipliers
commit: 86b8bff7e3ac6775113639d88db7448a8b47f0c1

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark