[RFT PATCH v1 1/5] Revert "usb: ehci-hcd: Keep async schedule running"

Lukasz Majewski
2020-03-24T18:11:24Z

Hi Marek,

> On 3/24/20 8:06 AM, Lukasz Majewski wrote:
> > Hi Marek,
>
> Hi,
>
> [...]
>
> >>>> You should probably figure out why this doesn't work first and
> >>>> then add fixes on top.
> >>>
> >>> Haven't you seen such problem during code development on your
> >>> setup when developing this patch?
> >>
> >> During the development of the patch, I don't remember, sorry. I
> >> most certainly saw various failure modes, however those should not
> >> be present mainline.
> >
> > The issue is that the qhtoken is not updated at all.
> >
> > Maybe you remember - is Linux using async setup by default (as
> > introduced in SHA1: 02b0e1a36c5bc20174299312556ec4e266872bd6) ?
>
> If I recall correctly, it is using async schedule for bulk transfers.
> But the code is available, so you can double-check that.
>
> >> I tested this patch with the problematic USB sticks on R-Car Gen3
> >> and with SMSC95xx USB ethernet adapter last weekend and I didn't
> >> see a problem.
> >
> > Ok.
> >
> > For i.MX6Q:
> > The SHA1: 02b0e1a36c5bc20174299312556ec4e266872bd6 patch causes the
> > iMX6Q to fail after a few minutes of testing. General in i.MX6Q the
> > usb is NOT robust at all.
> >
> > For i.MX53:
> > With patch 02b0e1a36c5bc20174299312556ec4e266872bd6 applied it also
> > breaks after a few minutes.
>
> So on CI HDRC , there is some difference in behavior. That is what you
> need to find and fix then.

The conclusion is that some boards/implementations are broken.

>
> > With this patch series applied it works for 2 days now without any
> > issue.
>
> Except performance is totally degraded

So we do have _very_ fast USB which breaks after a few minutes of
constant testing (with procedure stated earlier).

> and there is still no clear
> explanation _why_ any of these patches are needed

Haven't I explicitly explained in previous mails why XACTARR error shall
be handled? Nor the original thread did it? Wasn't the cover-letter
verbose enough?

> and/or whether doing
> write to a block device with these patches may cause data corruption.

So I will ask differently - what _may_ happen when the "TD -
token=XXXX" error shows up and the board hangs? Wouldn't we risk some
unwanted storage corruption?

Best regards,

Lukasz Majewski

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