On 11-07-18, 08:16, Robin Gong wrote: > > > The problem seems to be that we do not know whether we are doing > > > memcpy or not. Normally we get the information how a channel is to be > > > configured in dma_device->device_config, but this function is not > > > called in the memcpy case. > > > > Not really true, device_config only provides parameters to be configured for > > next slave transaction > > > > > An alternative might also be to do the setup in > > dma_device->device_prep_dma_memcpy. > > > > Precisely, see how other drivers do this > > > > Let's roll back a bit and foresee why is this required. > > > > In case of memcpy, you need to tell DMA to do transfer from src to dstn and > > size. Additional parameters like buswidth etc should be derived for maximum > > throughput (after all we are dma, people want it to be done > > fastest) > > > > Now for slave, you are interfacing with a peripheral and don't know how that is > > setup. So you need to match the parameters, otherwise you get overflow or > > underflow and hence need for device_config > > > > Please do not derive additional notions from these, please do not assume > > anything else, unless provided in documentation :) > I will move such prepare jobs from slave_config to device_prep_dma_memcpy > Instead of device_alloc_chan_resources as I did in v1, thus we have no 'chan->private' > issue, just like drivers/dma/stm32-mdma.c. The only limitation is those prepare jobs > (some register setting) will be done every time memcpy instead of only one time in slave_config > or v1 case. Is that ok? sounds fine to me -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
