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. 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
