On Fri, Jan 19, 2024 at 04:31:28PM -0500, Frank Li wrote: > From: Ran Wang <ran.wang_1@xxxxxxx> > > 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> > Reviewed-by: Peter Chen <peter.chen@xxxxxxx> > Signed-off-by: Frank Li <Frank.Li@xxxxxxx> > --- > Documentation/devicetree/bindings/usb/snps,dwc3.yaml | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml > index 203a1eb66691f..dbf272b76e0b5 100644 > --- a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml > +++ b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml > @@ -273,6 +273,13 @@ properties: > with an external supply. > type: boolean > > + snps,host-vbus-glitches: > + description: > + When set, power off all Root Hub ports immediately after > + setting host mode to avoid vbus (negative) glitch happen in later > + xhci reset. And the vbus will back to 5V automatically when reset done. > + type: boolean Why do we want to have a property for this at all? The commit message seems to describe a problem that's limited to specific configurations and appears to be somethng the driver should do unconditionally. Could you explain why this cannot be done unconditionally please? Thanks, Conor. > + > snps,is-utmi-l1-suspend: > description: > True when DWC3 asserts output signal utmi_l1_suspend_n, false when > -- > 2.34.1 >
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