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

[Sergei Shtylyov]

Hello!

On 06.06.2019 5:54, 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

   Enumeration. :-)

> 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@xxxxxxx>
> Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
[...]

MBR, Sergei