linux-kernel - Re: [PATCH v3] usb: dwc3: gadget: Add 1ms delay after end transfer command without IOC

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Date:   Tue, 28 Feb 2023 23:41:37 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Jack Pham <quic_jackp@...cinc.com>
CC:     Wesley Cheng <quic_wcheng@...cinc.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v3] usb: dwc3: gadget: Add 1ms delay after end transfer
 command without IOC

On Tue, Feb 28, 2023, Jack Pham wrote:
> On Tue, Feb 28, 2023 at 12:24:18PM -0800, Wesley Cheng wrote:
> > Previously, there was a 100uS delay inserted after issuing an end transfer
> > command for specific controller revisions.  This was due to the fact that
> > there was a GUCTL2 bit field which enabled synchronous completion of the
> > end transfer command once the CMDACT bit was cleared in the DEPCMD
> > register.  Since this bit does not exist for all controller revisions, add
> > the delay back in, and increase the duration to 1ms for the controller to
> > complete the command.
> > 
> > An issue was seen where the USB request buffer was unmapped while the DWC3
> > controller was still accessing the TRB.  However, it was confirmed that the
> > end transfer command was successfully submitted. (no end transfer timeout)
> > In situations, such as dwc3_gadget_soft_disconnect() and
> > __dwc3_gadget_ep_disable(), the dwc3_remove_request() is utilized, which
> > will issue the end transfer command, and follow up with
> > dwc3_gadget_giveback().  At least for the USB ep disable path, it is
> > required for any pending and started requests to be completed and returned
> > to the function driver in the same context of the disable call.  Without
> > the GUCTL2 bit, it is not ensured that the end transfer is completed before
> > the buffers are unmapped.
> > 
> > Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
> > ---
> > Changes in v3:
> > - Fixed subject title and modified commit text to reference the new 1ms
> > delay
> > 
> > Changes in v2:
> > - Increase delay value to 1ms
> > - Make this applicable to DWC32 revisions as well
> > 
> >  drivers/usb/dwc3/gadget.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index 3c63fa97a680..15adf07a4df4 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -1699,6 +1699,7 @@ static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
> >   */
> >  static int __dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force, bool interrupt)
> >  {
> > +	struct dwc3 *dwc = dep->dwc;
> >  	struct dwc3_gadget_ep_cmd_params params;
> >  	u32 cmd;
> >  	int ret;
> > @@ -1722,10 +1723,14 @@ static int __dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force, bool int
> >  	WARN_ON_ONCE(ret);
> >  	dep->resource_index = 0;
> >  
> > -	if (!interrupt)
> > +	if (!interrupt) {
> > +		if (DWC3_IP_IS(DWC32) || DWC3_IP_IS(DWC31) ||
> > +			DWC3_VER_IS_PRIOR(DWC3, 310A))
> 
> How about a little more succinctly:
> 
> 		if (!DWC3_IP_IS(DWC3) || DWC3_VER_IS_PRIOR(DWC3, 310A))
> ?
> 

or this:
	if (!DWC3_VER_IS_WITHIN(DWC3, 310A, ANY))


BR,
Thinh