On Wed, Aug 29, 2018 at 01:33:24PM +0200, Jan Kundrát wrote: > On čtvrtek 16. srpna 2018 14:54:49 CEST, Baolin Wang wrote: > > + * @word_delay: clock cycles to inter word delay after each word size > > + * (set by bits_per_word) transmission. > The description can be improved because it left me wondering what "clock > this is about. I suppose it's about the SPI clock cycles and not CPU clock > cycles, right? I'll be hapy to patch this once Baolin confirms that that is > the intended meaning. That's certainly how I read it. > It seems that this is only implemented in one newly added driver. I'm > interested in supporting this in spi-orion.c, but that sounds like > driver-specific work for something which is pretty generic. How should this > be implemented? Given that drivers for SPI masters can implement a function > which transfers several words at once, there are not that many better > possibilities than adding udelay()s, though. Thoughts? Yeah, you'd need to split the transfer into words and then add a delay between which would be rather expensive but it's about as good as we can get I think. > What is your plan to do with drivers which do not implement this (yet)? If a > spi_transfer gets queued which asks for a word_delay delay, it is silently > ignored now, AFAIU. Yes. A generic handler would be best. > What about userspace support, spidev and spi_ioc_transfer (that's my target, > actually)? Is it OK to s/pad/word_delay/ in the spidev code and pass that to > the generated struct spi_transfer? In my opinion, once we support specifying > this from userspace, one has to definitely check that the SPI controller is > ready to honor this request. Do we want a new bit in spi_controller.flags > for this? Not seeing pad in the spidev code? A feature flag would make sense along with a generic implementation.
Attachment:
signature.asc
Description: PGP signature
