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Date:   Sat, 9 Jan 2021 00:44:40 +0000
From:   Thinh Nguyen <>
To:     John Stultz <>,
        Felipe Balbi <>
CC:     lkml <>, Yu Chen <>,
        Tejas Joglekar <>,
        Yang Fei <>,
        YongQin Liu <>,
        Andrzej Pietrasiewicz <>,
        Jun Li <>,
        Mauro Carvalho Chehab <>,
        Greg Kroah-Hartman <>,
        Linux USB List <>,
        Heikki Krogerus <>,
        Roger Quadros <>
Subject: Re: [PATCH v3 1/2] usb: dwc3: Trigger a GCTL soft reset when
 switching modes in DRD


John Stultz wrote:
> On Fri, Jan 8, 2021 at 4:26 AM Felipe Balbi <> wrote:
>> Hi,
>> John Stultz <> writes:
>>> From: Yu Chen <>
>>> Just resending this, as discussion died out a bit and I'm not
>>> sure how to make further progress. See here for debug data that
>>> was requested last time around:
>>> With the current dwc3 code on the HiKey960 we often see the
>>> COREIDLE flag get stuck off in __dwc3_gadget_start(), which
>>> seems to prevent the reset irq and causes the USB gadget to
>>> fail to initialize.
>>> We had seen occasional initialization failures with older
>>> kernels but with recent 5.x era kernels it seemed to be becoming
>>> much more common, so I dug back through some older trees and
>>> realized I dropped this quirk from Yu Chen during upstreaming
>>> as I couldn't provide a proper rational for it and it didn't
>>> seem to be necessary. I now realize I was wrong.
>>> After resubmitting the quirk, Thinh Nguyen pointed out that it
>>> shouldn't be a quirk at all and it is actually mentioned in the
>>> programming guide that it should be done when switching modes
>>> in DRD.
>>> So, to avoid these !COREIDLE lockups seen on HiKey960, this
>>> patch issues GCTL soft reset when switching modes if the
>>> controller is in DRD mode.
>>> Cc: Felipe Balbi <>
>>> Cc: Tejas Joglekar <>
>>> Cc: Yang Fei <>
>>> Cc: YongQin Liu <>
>>> Cc: Andrzej Pietrasiewicz <>
>>> Cc: Thinh Nguyen <>
>>> Cc: Jun Li <>
>>> Cc: Mauro Carvalho Chehab <>
>>> Cc: Greg Kroah-Hartman <>
>>> Cc:
>>> Signed-off-by: Yu Chen <>
>>> Signed-off-by: John Stultz <>
>>> ---
>>> v2:
>>> * Rework to always call the GCTL soft reset in DRD mode,
>>>   rather then using a quirk as suggested by Thinh Nguyen
>>> v3:
>>> * Move GCTL soft reset under the spinlock as suggested by
>>>   Thinh Nguyen
>> Because this is such an invasive change, I would prefer that we get
>> Tested-By tags from a good fraction of the users before applying these
>> two changes.
> I'm happy to reach out to folks to try to get that. Though I'm
> wondering if it would be better to put it behind a dts quirk flag, as
> originally proposed?
> That way folks can enable it for devices as they need?
> Again, I'm not trying to force this in as-is, just mostly sending it
> out again for discussion to understand what other approach might work.
> thanks
> -john

A quirk would imply something is broken/diverged from the design right?
But it's not the case here, and at least this is needed for HiKey960.
Also, I think Rob will be ok with not adding 1 more quirk to the dwc3
devicetree. :)


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