Hi, Am 11.02.19 um 16:10 schrieb Lorenzo Bianconi: >> 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? not really. Compiling the mainline kernel with arm/multi_v7_defconfig it works. Using the same kernel but with arm64/defconfig doesn't work. But i don't think this is a 32/64 bit issue. The arm64 defconfig is much more complex (e.g. enables more IOMMU stuff). Regards Stefan
