From bca3c354c873d0c925c27e384e4758adf1ab2f05 Mon Sep 17 00:00:00 2001 From: Ran Wang Date: Wed, 16 Jan 2019 12:43:38 +0800 Subject: usb: dwc3: Add avoiding vbus glitch happen during xhci reset 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 Reviewed-by: Peter Chen --- Documentation/devicetree/bindings/usb/dwc3.txt | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'Documentation/devicetree/bindings/usb') diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt index 66780a47ad85..d2d5a8e99db5 100644 --- a/Documentation/devicetree/bindings/usb/dwc3.txt +++ b/Documentation/devicetree/bindings/usb/dwc3.txt @@ -109,6 +109,10 @@ Optional properties: more than one value, which means undefined length INCR burst type enabled. The values can be 1, 4, 8, 16, 32, 64, 128 and 256. + - snps,host-vbus-glitches: 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. + - in addition all properties from usb-xhci.txt from the current directory are supported as well -- cgit v1.2.3