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
