linux-kernel - RE: [PATCH v3 1/2] usb: dwc3: Add avoiding vbus glitch happen during xhci reset

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Date:   Wed, 27 Feb 2019 02:35:15 +0000
From:   Ran Wang <ran.wang_1@....com>
To:     Rob Herring <robh@...nel.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Yang Li <pku.leo@...il.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 1/2] usb: dwc3: Add avoiding vbus glitch happen during
 xhci  reset

Hi Rob,

> -----Original Message-----
> From: Rob Herring <robh@...nel.org>
> Sent: Wednesday, February 27, 2019 00:40
> To: Ran Wang <ran.wang_1@....com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Yang Li
> <pku.leo@...il.com>; linux-usb@...r.kernel.org; devicetree@...r.kernel.org;
> linux-kernel@...r.kernel.org; Ran Wang <ran.wang_1@....com>
> Subject: Re: [PATCH v3 1/2] usb: dwc3: Add avoiding vbus glitch happen during
> xhci reset
> 
> On Tue, 26 Feb 2019 06:59:21 +0000, Ran Wang wrote:
> > When DWC3 is set to host mode by programming register DWC3_GCTL, VBUS
> > (or its control signal) will turn on immediately on related Root Hub
> > ports. Then the VBUS will be de-asserted for a little while during
> > xhci reset (conducted by xhci driver) for a little while and back to normal.
> >
> > This VBUS glitch might cause some USB devices emuration fail if kernel
> > boot with them connected. One SW workaround which can fix this is to
> > program all PORTSC[PP] to 0 to turn off VBUS immediately after setting
> > host mode in DWC3 driver(per signal measurement result, it will be too
> > late to do it in xhci-plat.c or xhci.c).
> >
> > Signed-off-by: Ran Wang <ran.wang_1@....com>
> > ---
> > Changes in v3:
> >   - None
> >
> > Changes in v2:
> >   - Correct typos
> >   - Shorten the name to snps,host-vbus-glitches
> >
> >  Documentation/devicetree/bindings/usb/dwc3.txt |    3 +++
> >  1 files changed, 3 insertions(+), 0 deletions(-)
> >
> 
> Please add Acked-by/Reviewed-by tags when posting new versions. However,
> there's no need to repost patches *only* to add the tags. The upstream
> maintainer will do that for acks received on the version they apply.

Got it, thanks for telling me this. So if I need to update patch 2/2 in next version,
I still need to attach this 1/2 patch with adding tag 'Reviewed-by' to it, am I right?

> 
> If a tag was not added on purpose, please state why and what changed.

OK

Regards,
Ran