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. > Please not I have not received any confirm that this series fixes the reported issue > yet :) What is reported issue ? Thanks Stanislaw
