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

[Tan, Ley Foon]

> -----Original Message-----
> From: Marek Vasut <marex at denx.de>
> Sent: Monday, December 23, 2019 7:59 PM
> To: Tan, Ley Foon <ley.foon.tan at intel.com>; u-boot at lists.denx.de
> Cc: Ley Foon Tan <lftan.linux at gmail.com>; See, Chin Liang
> <chin.liang.see at intel.com>; Chee, Tien Fong <tien.fong.chee at intel.com>
> Subject: Re: [PATCH] usb: dwc2: Add small delay after reset
> 
> 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 ?
One way we can do is calling to reset_status() to read back reset status.
Will change that.

Regards
Ley Foon