Hi, On 28/01/2019 19:10, Mark Brown wrote:
On Sat, Jan 26, 2019 at 05:32:19PM +0100, Jonas Bonn wrote:@@ -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) */This needs some code in the core joining it up with the per-transfer word delay similar to what we have for speed_hz and bits_per_word in __spi_validate(). Then the controller drivers can just look at the per-transfer value and support both without having to duplicate logic.
So spi_transfer already has a field word_delay and it's defined as _clock cycles_ to delay between words. I defined word_delay in spi_device as _microseconds_ to delay along the lines of delay_usecs.
Given that the inter-word delay is a function of the slave device speed and not of the SPI bus speed, I'm inclined to say that a time-based delay is what we want (to be independent of bus speed). As such, I want to know if I should add word_delay_usecs to _both_ spi_transfer and spi_device?
There's only one user of word_delay from spi_transfer. Just looking at it quickly, it looks like it wants the word_delay in SPI-controller-clock cycles and not SCK cycles which seems pretty broken to me. Adding Baolin and Lanqing to CC: for comment. Could we rework that to be microseconds and do the calculation in the driver?
Thanks, Jonas
