diff options
author | Alexandru Ardelean <alexandru.ardelean@analog.com> | 2019-09-26 13:51:30 +0300 |
---|---|---|
committer | Mark Brown <broonie@kernel.org> | 2019-10-15 11:41:25 +0100 |
commit | b2c98153f45fc17b9fcb241000f2d131ddea6030 (patch) | |
tree | ad1dfe368dfdd06fde52314f569bf1feefe6c534 /drivers/spi | |
parent | 6b3f236a998550dba91a46a22feb1cc02f39fb06 (diff) | |
download | linux-b2c98153f45fc17b9fcb241000f2d131ddea6030.tar.gz linux-b2c98153f45fc17b9fcb241000f2d131ddea6030.tar.bz2 linux-b2c98153f45fc17b9fcb241000f2d131ddea6030.zip |
spi: introduce spi_delay struct as "value + unit" & spi_delay_exec()
There are plenty of delays that have been introduced in SPI core. Most of
them are in micro-seconds, some need to be in nano-seconds, and some in
clock-cycles.
For some of these delays (related to transfers & CS timing) it may make
sense to have a `spi_delay` struct that abstracts these a bit.
The important element of these delays [for unification] seems to be the
`unit` of the delay.
It looks like micro-seconds is good enough for most people, but every-once
in a while, some delays seem to require other units of measurement.
This change adds the `spi_delay` struct & a `spi_delay_exec()` function
that processes a `spi_delay` object/struct to execute the delay.
It's a copy of the `cs_change_delay` mechanism, but without the default
for 10 uS.
The clock-cycle delay unit is a bit special, as it needs to be bound to an
`spi_transfer` object to execute.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20190926105147.7839-3-alexandru.ardelean@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi')
-rw-r--r-- | drivers/spi/spi.c | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 7ba981cdb86b..7499a4efbaba 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1106,6 +1106,57 @@ static void _spi_transfer_delay_ns(u32 ns) } } +static int _spi_delay_to_ns(struct spi_delay *_delay, struct spi_transfer *xfer) +{ + u32 delay = _delay->value; + u32 unit = _delay->unit; + u32 hz; + + if (!delay) + return 0; + + switch (unit) { + case SPI_DELAY_UNIT_USECS: + delay *= 1000; + break; + 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 + */ + hz = xfer->effective_speed_hz ?: xfer->speed_hz / 2; + if (!hz) + return -EINVAL; + delay *= DIV_ROUND_UP(1000000000, hz); + break; + default: + return -EINVAL; + } + + return delay; +} + +int spi_delay_exec(struct spi_delay *_delay, struct spi_transfer *xfer) +{ + int delay; + + if (!_delay) + return -EINVAL; + + delay = _spi_delay_to_ns(_delay, xfer); + if (delay < 0) + return delay; + + _spi_transfer_delay_ns(delay); + + return 0; +} +EXPORT_SYMBOL_GPL(spi_delay_exec); + static void _spi_transfer_cs_change_delay(struct spi_message *msg, struct spi_transfer *xfer) { |