> On 31.03.2015, at 05:28, Stephen Warren <swar...@wwwdotorg.org> wrote: >> + /* check if we shall run in polling mode */ >> + xfer_time_us = tfr->len * 9 * 1000000 / spi_used_hz; > > Why 9 not 8; presumably thats bits per byte, and IIRC SPI doesn't have > anything like I2C's ack bit per byte?
Well - the bcm2835 make a 1 cycle wait after each byte transferred. Hence 9 bit actual length we need to account for. Actually on top of that there are 3 more cycles when bringing the SPI hardware active (at least with native CS) - but these are minimal offsets. Martin -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
