[BACKPORT 4.14.y 04/18] usb: dwc3: Allow disabling of metastability workaround

[Greg KH]

On Thu, Sep 05, 2019 at 10:17:45AM -0600, Mathieu Poirier wrote:
> From: Roger Quadros <rogerq at ti.com>
> 
> commit 42bf02ec6e420e541af9a47437d0bdf961ca2972 upstream
> 
> Some platforms (e.g. TI's DRA7 USB2 instance) have more trouble
> with the metastability workaround as it supports only
> a High-Speed PHY and the PHY can enter into an Erratic state [1]
> when the controller is set in SuperSpeed mode as part of
> the metastability workaround.
> 
> This causes upto 2 seconds delay in enumeration on DRA7's USB2
> instance in gadget mode.
> 
> If these platforms can be better off without the workaround,
> provide a device tree property to suggest that so the workaround
> is avoided.
> 
> [1] Device mode enumeration trace showing PHY Erratic Error.
>      irq/90-dwc3-969   [000] d...    52.323145: dwc3_event: event (00000901): Erratic Error [U0]
>      irq/90-dwc3-969   [000] d...    52.560646: dwc3_event: event (00000901): Erratic Error [U0]
>      irq/90-dwc3-969   [000] d...    52.798144: dwc3_event: event (00000901): Erratic Error [U0]

Does the DT also need to get updated with this new id for this?  Is that
a separate patch somewhere?

thanks,

greg k-h