Some devices are slow and cannot keep up with the SPI bus and therefore require a short delay between words of the SPI transfer.
The example of this that I'm looking at is a SAMA5D2 with a minimum SPI clock of 400kHz talking to an AVR-based SPI slave. The AVR cannot put bytes on the bus fast enough to keep up with the SoC's SPI controller even at the lowest bus speed. This patch introduces the ability to specify a required inter-word delay for SPI devices. It is up to the controller driver to configure itself accordingly in order to introduce the requested delay. Signed-off-by: Jonas Bonn <[email protected]> CC: Mark Brown <[email protected]> CC: Rob Herring <[email protected]> CC: Mark Rutland <[email protected]> CC: [email protected] CC: [email protected] --- include/linux/spi/spi.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 314d922ca607..8e410de02af4 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -118,6 +118,8 @@ void spi_statistics_add_transfer_stats(struct spi_statistics *stats, * for driver coldplugging, and in uevents used for hotplugging * @cs_gpio: gpio number of the chipselect line (optional, -ENOENT when * not using a GPIO line) + * @word_delay: microsecond delay to be inserted between consecutive words + * of a transfer * * @statistics: statistics for the spi_device * @@ -164,6 +166,7 @@ struct spi_device { char modalias[SPI_NAME_SIZE]; const char *driver_override; int cs_gpio; /* chip select gpio */ + uint16_t word_delay; /* inter-word delay (us) */ /* the statistics */ struct spi_statistics statistics; -- 2.19.1
