Re: [PATCH 2/2] dma: xilinx: dpdma: Add the Xilinx DisplayPort DMA engine driver

[Vinod Koul <vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Wed, Jan 24, 2018 at 05:45:00PM +0000, Hyun Kwon wrote:

> > > > > +static int xilinx_dpdma_config(struct dma_chan *dchan,
> > > > > +			       struct dma_slave_config *config)
> > > > > +{
> > > > > +	if (config->direction != DMA_MEM_TO_DEV)
> > > > > +		return -EINVAL;
> > > >
> > > > ?? Why are the config values not used, how else do you configure the
> > > > channel?
> > > >
> > >
> > > There's not much configuration to be done. Channels are pretty much
> > identical
> > > with fixed configurations.
> > 
> > hmmm, you do support DMA_SLAVE right?
> > 
> 
> Yes, and it's single direction, DMA_MEM_TO_DEV.

Okay how do you find the DMA data width and the burst to apply when you DMA
to device? Are these not programmable?

I think you need to go back and check that part. Moreover a client may send
you parameters and program the Device FIFO, you not honoring those will
result in bad data received on Device, am sure you don't want that

-- 
~Vinod
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