Re: [PATCH v4] fsl/usb: Workarourd for USB erratum-A005697
From: Alan Stern
Date: Wed Nov 30 2016 - 10:23:00 EST
On Tue, 29 Nov 2016, Changming Huang wrote:
> The EHCI specification states the following in the SUSP bit description:
> In the Suspend state, the port is sensitive to resume detection.
> Note that the bit status does not change until the port is suspended and
> that there may be a delay in suspending a port if there is a transaction
> currently in progress on the USB.
> However, in NXP USBDR controller, the PORTSCx[SUSP] bit changes immediately
> when the application sets it and not when the port is actually suspended.
> So the application must wait for at least 10 milliseconds after a port
> indicates that it is suspended, to make sure this port has entered
> suspended state before initiating this port resume using the Force Port
> Resume bit. This bit is for NXP controller, not EHCI compatible.
> Signed-off-by: Changming Huang <jerry.huang@xxxxxxx>
> Signed-off-by: Ramneek Mehresh <ramneek.mehresh@xxxxxxx>
> Changes in v4:
> - release spinlock before sleeping
> Changes in v3:
> - add 10ms delay in function ehci_hub_control
> - fix typos
> Changes in v2:
> - move sleep out of spin-lock
> - add more comment for this workaround
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>