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 <ran.wang_1@xxxxxxx> > --- > 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@xxxxxxxxxx>
