On Mon, Jun 02, 2014 at 04:55:14PM +0200, Geert Uytterhoeven wrote: > On Mon, Jun 2, 2014 at 4:42 PM, Mark Brown <broonie@xxxxxxxxxx> wrote: > > Hrm, was this error handling or is it a hardware limitation that it can > > only do DMA in one direction? Perhaps the core ought to be changed to > > support that if it's a hardware limit, I honestly hadn't considered that > > possibility when I wrote the code. > So it's not a hardware limitation, but a software optimization ;-) > If there's no data to receive, RSPI on SH can do transmit only. > If there's data to receive, it must do both transmit and receive. ... > Hence if only one DMA channel is available, RSPI on SH could still do DMA TX > before. I don't know whether anyone ever used this, as there were no in-tree > users of RSPI DMA. OK, that is quite common I guess in hardware where the number of DMA channels is limited (which does exist). We should probably support it at some point.
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