Hi Laurent, On 20-12-19, 07:13, Laurent Pinchart wrote: > > OK, in the light of this information I'll keep the two separate and will > > switch to vchan as requested by Vinod. > > I've moved forward with this task, but eventually ran into one hack in > the driver that is more difficult to get rid of than the other ones. > > For display operation, the DPSUB driver needs to submit cyclic > interleaved transfer requests. There's no such thing (as far as I can > tell) in the DMA engine API, so the DPDMA drive simply keeps processing we do support interleave, you need to implement .device_prep_interleaved_dma and use dmaengine_prep_interleaved_dma() from the client > the same descriptor over and over again until a new one is issued. The > hardware supports this with the help of hardware-based chaining of > descriptors, and the DPDMA driver simply sets the next pointer of the > descriptor to itself. > > How can I solve this in a way that wouldn't abuse the DMA engine API ? Is this not a cyclic case of descriptor? -- ~Vinod
