On Thu, Aug 20, 2015 at 10:30:50AM -0700, Sudeep Dutt wrote: > On Thu, 2015-08-20 at 10:50 +0530, Vinod Koul wrote: > > On Mon, Jul 27, 2015 at 04:58:17PM -0700, Ashutosh Dixit wrote:
> > > + /* > > > + * This is a hack to program status descriptor since > > > + * DMA engine API doesn't have support for this. > > > + */ > > what do you mean by programming status descriptor, what do you need to > > program? > > > > The MIC X100 DMA engine has a special status descriptor which writes an > 8 byte immediate data value to a destination address. It is used to > signal completion of all DMA descriptors prior to the status descriptor. > The DMA engine API does not allow drivers to pass a 8 byte value. We are > allowed to pass a source physical address but we cannot determine the > source value within the DMA driver using that information specifically > with the IOMMU enabled. We have added this workaround so that we can > program this special status update descriptor without making any changes > to the DMA engine API. I think this is a special case so you should export an API and let client program using that API. -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
