On Jan 16, Stanislaw Gruszka wrote: > On Wed, Jan 16, 2019 at 12:44:33PM +0100, Lorenzo Bianconi wrote: > > > On Tue, Jan 15, 2019 at 04:47:47PM +0100, Lorenzo Bianconi wrote: > > > > Hi Stanislaw, > > > > > > Hi :-) > > > > > > > > Not sure what is the problem , but this patch set look like a workaround > > > > > not fix. If this an issue with IOMMU and sg, seems there is something wrong > > > > > in sg page mappings eigher on mt76 dirver or IOMMU driver. > > > > > > > > The main point here I guess is we do not need sg if fragment number is one (e.g > > > > usb2.0). Moreover this can fix IOMMU reported issues. > > > > > > So there if diffrence for USB host driver when we have one usb->sg > > > sengment and if we just pass the buffer via urb->transfer_buf . I think > > > most USB host drivers behave the same in such cases. For what USB > > > hardware/driver this is needed ? Perhaps simpler fix could be done > > > in USB host driver? > > > > According to https://github.com/torvalds/linux/blob/master/drivers/usb/core/hcd.c#L1557 > > single sg urb and urb with a configured transfer_buf are managed in a different way. > > But this should not make any difference for underlying low level USB > host driver, since we map 1 buffer of the same size, just by using > different routines for that. probably amd iommu has some constraints on sg buffer layout respect to intel one, not sure > > > Please not I have not received any confirm that this series fixes the reported issue > > yet :) > > What is reported issue ? https://marc.info/?l=linux-wireless&m=154716096506037&w=2 Regards, Lorenzo > > Thanks > Stanislaw
