diff options
| author | Jonas Bonn <jonas@norrbonn.se> | 2019-01-30 09:40:05 +0100 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2019-01-30 23:02:11 +0000 |
| commit | 473a78a7bbeb7c77b81b596095f59ce4fbbd49dc (patch) | |
| tree | 8e499db920a1f02fd4ac2a20f1105442c92aa64b /drivers/spi/spi-atmel.c | |
| parent | b7bb367afa4bf9de60830683305c63030c3e581d (diff) | |
| download | lwn-473a78a7bbeb7c77b81b596095f59ce4fbbd49dc.tar.gz lwn-473a78a7bbeb7c77b81b596095f59ce4fbbd49dc.zip | |
spi-atmel: support inter-word delay
If the SPI slave requires an inter-word delay, configure the DLYBCT
register accordingly.
Tested on a SAMA5D2 board (derived from SAMA5D2-Xplained reference
board).
Signed-off-by: Jonas Bonn <jonas@norrbonn.se>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
CC: Nicolas Ferre <nicolas.ferre@microchip.com>
CC: Mark Brown <broonie@kernel.org>
CC: Alexandre Belloni <alexandre.belloni@bootlin.com>
CC: Ludovic Desroches <ludovic.desroches@microchip.com>
CC: linux-spi@vger.kernel.org
CC: linux-arm-kernel@lists.infradead.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi/spi-atmel.c')
| -rw-r--r-- | drivers/spi/spi-atmel.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c index f53f0c5e63da..4954f0ab1606 100644 --- a/drivers/spi/spi-atmel.c +++ b/drivers/spi/spi-atmel.c @@ -1201,13 +1201,14 @@ static int atmel_spi_setup(struct spi_device *spi) csr |= SPI_BIT(CSAAT); /* DLYBS is mostly irrelevant since we manage chipselect using GPIOs. - * - * DLYBCT would add delays between words, slowing down transfers. - * It could potentially be useful to cope with DMA bottlenecks, but - * in those cases it's probably best to just use a lower bitrate. */ csr |= SPI_BF(DLYBS, 0); - csr |= SPI_BF(DLYBCT, 0); + + /* DLYBCT adds delays between words. This is useful for slow devices + * that need a bit of time to setup the next transfer. + */ + csr |= SPI_BF(DLYBCT, + (as->spi_clk / 1000000 * spi->word_delay_usecs) >> 5); asd = spi->controller_state; if (!asd) { |