> 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, > > > > [email protected] wrote: > > > > > From: Lorenzo Bianconi <[email protected]> > > > > > > > > > > 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.
In my series I: 1- set num_sg to 0 2- use transfer_buffer please correct me if I am wrong but in your solution you did the same since AFAIK PageHighMem is always 0 so you end up setting num_sg to 0 and using transfer_buffer as well. Is my understanding correct? > > > Moreover with this approach we avoid some unnecessary operation in the > > hotpath > > What unnecessary operation ? the ones in mt76u_fill_bulk_urb() Regards, Lorenzo > > Stanislaw
