On Tue, Feb 12, 2019 at 03:09:53PM +0100, Lorenzo Bianconi wrote:
> >
> > (repost with corrected Lorenzo email)
> >
> > On Tue, Feb 12, 2019 at 02:45:50PM +0100, Stanislaw Gruszka wrote:
> > > On Tue, Feb 12, 2019 at 02:24:47PM +0100, LorenzoBianconilorenzo@xxxxxxxxxx wrote:
> > > > From: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
> > > >
> > > > Use linear fragment and not a single usb scatter-gather buffer in mt76u
> > > > {tx,rx} datapath if the usb controller has sg data length constraints.
> > > > Moreover add disable_usb_sg module parameter in order to explicitly
> > > > disable scatter-gather. SG I/O is not supported by all host drivers and
> > > > some users have reported sg issues on AMD IOMMU.
> > >
> > > Again. This is not right approach. SG issues should be fixed
> > > not workarounded.
>
> Hi Stanislaw,
>
> here we do not use SG, so num_sg is 0 and we use transfer_buffer. I do
> not see how I am working around the issue.
By avoiding SG buffer allocation and configuration which most likely
need to be fixed.
> Moreover with this approach we avoid some unnecessary operation in the hotpath
What unnecessary operation ?
Stanislaw
