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Date:   Tue, 8 Sep 2020 08:49:15 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
To:     Felipe Balbi <balbi@kernel.org>
Cc:     Yu Chen <chenyu56@huawei.com>,
        Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, john.stultz@linaro.org,
        suzhuangluan@hisilicon.com, kongfei@hisilicon.com,
        liuyu712@hisilicon.com, wanghu17@hisilicon.com,
        butao@hisilicon.com, chenyao11@huawei.com,
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        xuyoujun4@huawei.com, yudongbin@hisilicon.com,
        zangleigang@hisilicon.com,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Binghui Wang <wangbinghui@hisilicon.com>
Subject: Re: [PATCH v6 04/13] usb: dwc3: Add splitdisable quirk for
 Hisilicon Kirin Soc
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Em Tue, 08 Sep 2020 09:09:46 +0300
Felipe Balbi <balbi@kernel.org> escreveu:

> >> Why does it affect only Hikey kirin?   
> >
> > As John Stultz didn't re-submit this one (and looking at the DT
> > between Kirin 960 and 970 from the original Kernel 4.9 official
> > drivers), I suspect that only Kirin 970 requires this quirk.
> >
> > It could well be due to some Dwc3 revision, but it could also be due
> > to some differences at the USB part of the SoC, as there are a  
> 
> the reason I ask is that if it's caused by dwc3 revision, then we don't
> need the extra dt property, we can rely on a revision check. If it's
> something that can't be detected in runtime, then we need a property.

Yeah, if it would be possible to auto-detect, that would be
better. Yet, hard to say if it would be possible to do that, 
without access to the Dwc3 docs, and without different hardware 
for testing it.

> > few other things different between hikey 960 and 970: it has a
> > different PHY driver, and there are also some differences at the
> > USB HUB which is connected into it.
> >
> > On both devices, the USB physical ports are actually connected
> > into a HUB. In the case of Hikey 970, the hub seems to be a
> > TI TUSB8041 4-Port Hub:
> > 	
> > 	$ lsusb
> > 	Bus 002 Device 002: ID 0451:8140 Texas Instruments, Inc. TUSB8041 4-Port Hub
> > 	Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> > 	Bus 001 Device 004: ID 090c:1000 Silicon Motion, Inc. - Taiwan (formerly Feiya Technology Corp.) Flash Drive
> > 	Bus 001 Device 003: ID 413c:301a Dell Computer Corp. Dell MS116 Optical Mouse
> > 	Bus 001 Device 002: ID 0451:8142 Texas Instruments, Inc. TUSB8041 4-Port Hub
> > 	Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> >  
> >> What's the dwc3 revision on
> >> that SoC (grep SNPSID /sys/kernel/debugfs/*dwc3/regdump)?  
> >
> > 	GSNPSID = 0x33313130  
> 
> This isn't even listed as a known revision in dwc3/core.h. Thinh, could
> the issue being described here caused by a known Erratum with this
> particular revision?

Maybe. Again, hard to tell without any documentation from Synopsys.

Maybe some of the Synopsys folks at USB MK can shed a light.

Thanks,
Mauro