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

Hi Rob,

-----Original Message-----
From: Rob Herring <robh@kernel.org>
Sent: Wednesday, February 27, 2019 00:40
To: Ran Wang <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Yang Li
[off-list ref]; linux-usb@vger.kernel.org; devicetree@vger.kernel.org;
linux-kernel@vger.kernel.org; Ran Wang [off-list ref]
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:

quoted

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 <redacted>
---
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