The Microchip USB251xB hub, according to its datasheet, is operational 500us after deasserting reset on startup and can then be attached or configured. I ran into a batch of such hubs, of the 2512Bi variant, that didn't appear to work or only worked sporadically. Debugging the issue revealed that these specific hubs do not typically manage to reset within 500us. Instead they become operational 800us or so after deasserting the RESET_N signal. This is probably a faulty batch of the chips but making the reset delay configurable through dt bindings allows these chips to be used. Daniels Umanovskis (2): dt-bindings: usb: usb251xb: add documentation for reset-delay-us usb: usb251xb: make power-up reset delay configurable in device tree Documentation/devicetree/bindings/usb/usb251xb.txt | 2 ++ drivers/usb/misc/usb251xb.c | 6 +++++- 2 files changed, 7 insertions(+), 1 deletion(-) -- 2.30.2
