[PATCH] usb: dwc2: Add small delay after reset

[Marek Vasut]

On 12/23/19 9:07 AM, Ley Foon Tan wrote:
> In Cyclone 5 SoC platform, the first USB probing is failed but second
> probing is success. DWC2 driver read gsnpsid register right after de-assert
> reset, but controller is not ready yet and it returns gsnpsid 0.
> Adding small delay after de-assert reset solve the issue.
> 
> Retry with this fix more than 10 times without issue.
> 
> => usb reset
> resetting USB...
> Bus usb at ffb40000: usb probe
> SNPSID invalid (not DWC2 OTG device): 00000000
> Port not available.
> => usb reset
> resetting USB...
> Bus usb at ffb40000: usb probe
> scanning bus usb at ffb40000 for devices... 2 USB Device(s) found
>        scanning usb for storage devices... 1 Storage Device(s) found

Can't you poll for the readiness of the IP somehow instead of using
arbitrary delay ?