> Hi Lorenzo, > > Am 11.02.19 um 12:06 schrieb Lorenzo Bianconi: > >> Hi, > >> > >> Am 11.02.19 um 11:04 schrieb Lorenzo Bianconi: > >>>> On Sun, Feb 10, 2019 at 11:22:25AM +0100, Lorenzo Bianconi wrote: > >>>>>> On Sat, Feb 09, 2019 at 09:29:05PM +0100, Stefan Wahren wrote: > >>>>>>>> could you please test the following series: > >>>>>>>> https://patchwork.kernel.org/cover/10764453/ > >>>>>>> yeah this fixed the probing timeout and the driver will probe successful. AFAIK the dwc2 host mode doesn't support scatter-gather yet. > >>>>>> So this is either dwc2 scatter-gather problem which should be addressed in > >>>>>> this driver or mt76x0u does something wrong when configuring SG. > >>>>>> > >>>>>> Disabling SG is just workaround, which do not address actual problem. > >>>>>> > >>>>>> I think I found mt76x0u issue that could cause this USB probe error > >>>>>> (and possibly also address AMD IOMMU issue). We seems do not correctly > >>>>>> set URB transfer length smaller than sg buffer length. Attached patch > >>>>>> should correct that. > >>>>> Hi Stanislaw, > >>>>> > >>>>> I think 'sg[0].length' is already set in mt76u_fill_rx_sg(). > >>>> It is, buf->len and sg[0].length are initialized to the same value for 1 > >>>> segment. But then buf->len (assigned to urb->buffer_transfer_length) change > >>>> to smaller value , but sg[0].length stay the same. What I think can be > >>>> problem for usb host driver. > >>>> > >>>>> Moreover applying this patch I got the following crash (rpi-5.0.y): > >>>> Ok, so with patch probe fail instantly and trigger yet another bug(s) > >>>> on error path. You seems to address that already. > >>>> > >>>>> Moreover for mt76x0u SG is 'already' disabled since we use just one > >>>>> buffer so from performance point of view I do not see any difference > >>>>> of using a standard usb buffer. > >>>>> This patch has been tested in multiple scenarios and seems to fix > >>>>> reported issues (for usb2.0). > >>>> Ok, so passing buffer via urb->transfer_buffer works. But why urb->sg > >>>> does not work for 1 segment ? > >>> Here it is a different issue respect to the AMD IOMMU one, dwc2 host driver > >>> does not implement SG I/O so probing fails. I guess it is still useful to > >>> implement a 'legacy' mode that enable mt76 on host controllers that do not implement > >>> SG I/O (rpi is a very common device so it will be cool to have mt76 working on > >>> it). Moreover we are not removing functionalities, user experience will remain > >>> the same > >>> > >> i'm not sure that you understand my mail [1] with the summary of my test > >> results. > >> > > Yes right, I did not get it sorry :) > > as indicated here https://www.raspberrypi.org/documentation/linux/kernel/building.md > > I am using bcm2709_defconfig config (using it I spotted the mt76 crashes and > > probe failure) > > no problem, at the beginning this could be very confusing. I only want > to clarify that this documentation refers to the vendor kernel (with a > different USB host driver) of the Raspberry Pi Foundation. > > All my results refers to the mainline kernel we all should talk about. I > started a gist which try to describe the mainline variant: > https://gist.github.com/lategoodbye/c7317a42bf7f9c07f5a91baed8c68f75 So to summarize: - Raspberry Pi Foundation kernel works just with RFC series - mainline kernel works out of the box is my understanding correct? I am still considering adding a legacy mode since there will not be any regression using it instead of SG I/O with just one SG buffer Regards, Lorenzo > > Maybe this could be helpful. > > Stefan > > > Regards, > > Lorenzo > > > >> In case of using the arm/multi_v7_defconfig (32 bit) the mt76 works like > >> a charm without your sg avoid patch series, but the arm64/defconfig (64 > >> bit) requires the series to probe at least. So i wouldn't conclude from > >> the fact that dwc2 doesn't support SG any probing issues on arm64. So we > >> need to investigate which config option triggers the problem. > >> > >> Stefan > >> > >> [1] - https://marc.info/?l=linux-usb&m=154981675724078 > >>
