Re: [PATCH v2 1/2] usb: dwc3: Add avoiding vbus glitch happen during xhci reset

On Tue, 19 Feb 2019 07:23:14 +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 <redacted>
---
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(-)

Reviewed-by: Rob Herring <robh@kernel.org>