Subject: Re: [BUG] mt76x0u: Probing issues on Raspberry Pi 3 B+
To:     Stanislaw Gruszka <sgruszka@redhat.com>
Cc:     Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Felix Fietkau <nbd@nbd.name>,
        Doug Anderson <dianders@chromium.org>,
        Minas Harutyunyan <hminas@synopsys.com>,
        USB list <linux-usb@vger.kernel.org>,
        linux-wireless <linux-wireless@vger.kernel.org>
References: <20190211173315.GE6292@redhat.com>
 <Pine.LNX.4.44L0.1902111246410.1543-100000@iolanthe.rowland.org>
 <CAJ0CqmVFVBXi5E07-ZsYojC7mP4ogpwbcDkDTeebHwX+ayz2DQ@mail.gmail.com>
 <20190212093035.GB12906@redhat.com>
 <404607590.373282.1550126997144@email.ionos.de>
 <20190214092530.GA17273@redhat.com>
From:   Stefan Wahren <stefan.wahren@i2se.com>
Message-ID: <878a7160-2e91-d057-6d27-c6b9d85f700e@i2se.com>
Date:   Thu, 14 Feb 2019 10:48:15 +0100
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Hi Stanislaw,

Am 14.02.19 um 10:25 schrieb Stanislaw Gruszka:
> On Thu, Feb 14, 2019 at 07:49:57AM +0100, Stefan Wahren wrote:
>> Hi Stanislaw,
>>
>>> Stanislaw Gruszka <sgruszka@redhat.com> hat am 12. Februar 2019 um 10:30 geschrieben:
>>>
>>>
>>>
>>> In usb_sg_init() urb->num_sgs is set 0 for sg_tablesize = 0 controllers.
>>> In mt76 we set urb->num_sgs to 1. I thought it is fine, but now I think
>>> this is bug. We can fix that without changing allocation method and
>>> still use SG allocation. Attached patch do this, please check if it works
>>> on rpi. Patch is on top of your error path fixes.
>> your patch didn't apply cleanly to yesterdays next. After some minor manual fixup, i was able to build them and here are the results starting from boot (please ignore the invalid time in the kernel log):
>> https://gist.github.com/lategoodbye/33bd5bc75b9fc935faa231bc472defa8
> I think this is due to urb->transfer_length and sg[0]->length mismatch,
> which should be addressed by my other patch. I'm attaching the patch
> rebased on -next with this line integrated, please test. 
>
> But there could be other bug's in mt76-usb SG code.
Will retry
>
>> Using multi_v7_defconfig i'm getting a warning on the first connect and always this flood of rx urb failed on disconnect. The driver seems to probe but isn't functional even after 2 tries.
>>
>> Using arm64_defconfig i don't get any warning. But except of this i'm getting similiar results to multi_v7_defconfig.
>>
>> So in comparison, Lorenzo's workaround behaves better.
> I'm pretty sure problem is mt76x0u 4.19 -> 4.20 regression intrduced by
> integrating mt76x0u in mt76-usb (things do not work from day 0
> for mt76x2u). We should find fix(es) that will be proper for -stable.
So i should also try 4.19 without any patches?
>
> Stanislaw