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author | Alexandru Ardelean <alexandru.ardelean@analog.com> | 2019-09-26 13:51:30 +0300 |
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committer | Mark Brown <broonie@kernel.org> | 2019-10-15 11:41:25 +0100 |
commit | b2c98153f45fc17b9fcb241000f2d131ddea6030 (patch) | |
tree | ad1dfe368dfdd06fde52314f569bf1feefe6c534 | |
parent | 6b3f236a998550dba91a46a22feb1cc02f39fb06 (diff) | |
download | linux-b2c98153f45fc17b9fcb241000f2d131ddea6030.tar.bz2 |
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>
-rw-r--r-- | drivers/spi/spi.c | 51 | ||||
-rw-r--r-- | include/linux/spi/spi.h | 18 |
2 files changed, 66 insertions, 3 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) { diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 27f6b046cf92..8f643de3197b 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -91,6 +91,21 @@ void spi_statistics_add_transfer_stats(struct spi_statistics *stats, SPI_STATISTICS_ADD_TO_FIELD(stats, field, 1) /** + * struct spi_delay - SPI delay information + * @value: Value for the delay + * @unit: Unit for the delay + */ +struct spi_delay { +#define SPI_DELAY_UNIT_USECS 0 +#define SPI_DELAY_UNIT_NSECS 1 +#define SPI_DELAY_UNIT_SCK 2 + u16 value; + u8 unit; +}; + +extern int spi_delay_exec(struct spi_delay *_delay, struct spi_transfer *xfer); + +/** * struct spi_device - Controller side proxy for an SPI slave device * @dev: Driver model representation of the device. * @controller: SPI controller used with the device. @@ -887,9 +902,6 @@ struct spi_transfer { u16 delay_usecs; u16 cs_change_delay; u8 cs_change_delay_unit; -#define SPI_DELAY_UNIT_USECS 0 -#define SPI_DELAY_UNIT_NSECS 1 -#define SPI_DELAY_UNIT_SCK 2 u32 speed_hz; u16 word_delay; |