On Fri, Mar 08, 2019 at 12:55:52AM +0000, Trent Piepho wrote: > On Thu, 2019-03-07 at 10:30 +0000, Mark Brown wrote: > > On Wed, Mar 06, 2019 at 06:57:12PM +0000, Trent Piepho wrote: > > > High speed receive operations may be less likely to have issues > > > with > > > FIFO overflow when using DMA than when using PIO. > > > The eCSPI appears to insert a 4 bit pause after each word in DMA > > > mode, > > > not done in PIO mode, which can make DMA transfers 50% slower than > > > PIO. > > Wow, that's... innovative. If that's the case can't the decision > > function for switching to DMA be tweaked to take into account slave > > mode operation instead? > Do you mean slave mode as in the imx being the spi slave and the > external device the master? That's not being used here. Sorry, not sure where I got that from. Must've just switched from another mail talking about that or something. The point still stands though, can't we handle this by adjusting the decision function? Though there's an unfortunate system load/performance tradeoff... If we can't do that then I think a runtime control with a device property in sysfs would be a good idea as well.
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