linux-kernel - RE: [PATCH v2 1/1] usb: dwc2: gadget: parity fix in isochronous mode

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Date:	Wed, 9 Sep 2015 18:16:00 +0000
From:	Roman Bacik <rbacik@...adcom.com>
To:	John Youn <John.Youn@...opsys.com>,
	Scott Branden <sbranden@...adcom.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>
Subject: RE: [PATCH v2 1/1] usb: dwc2: gadget: parity fix in isochronous mode

> -----Original Message-----
> From: John Youn [mailto:John.Youn@...opsys.com]
> Sent: September-03-15 11:53 PM
> To: Scott Branden; John Youn; Greg Kroah-Hartman; linux-
> usb@...r.kernel.org; Roman Bacik
> Cc: linux-kernel@...r.kernel.org; bcm-kernel-feedback-list
> Subject: Re: [PATCH v2 1/1] usb: dwc2: gadget: parity fix in isochronous mode
> 
> On 8/31/2015 9:17 AM, Scott Branden wrote:
> > From: Roman Bacik <rbacik@...adcom.com>
> >
> > USB OTG driver in isochronous mode has to set the parity of the
> > receiving microframe. The parity is set to even by default. This
> > causes problems for an audio gadget, if the host starts transmitting on odd
> microframes.
> >
> > This fix uses Incomplete Periodic Transfer interrupt to toggle between
> > even and odd parity until the Transfer Complete interrupt is received.
> >
> > Signed-off-by: Roman Bacik <rbacik@...adcom.com>
> > Reviewed-by: Abhinav Ratna <aratna@...adcom.com>
> > Reviewed-by: Srinath Mannam <srinath.mannam@...adcom.com>
> > Signed-off-by: Scott Branden <sbranden@...adcom.com>
> > ---
> >  drivers/usb/dwc2/core.h   |  1 +
> >  drivers/usb/dwc2/gadget.c | 51
> ++++++++++++++++++++++++++++++++++++++++++++++-
> >  drivers/usb/dwc2/hw.h     |  1 +
> >  3 files changed, 52 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h index
> > 0ed87620..a5634fd 100644
> > --- a/drivers/usb/dwc2/core.h
> > +++ b/drivers/usb/dwc2/core.h
> > @@ -150,6 +150,7 @@ struct s3c_hsotg_ep {
> >  	unsigned int            periodic:1;
> >  	unsigned int            isochronous:1;
> >  	unsigned int            send_zlp:1;
> > +	unsigned int            has_correct_parity:1;
> >
> >  	char                    name[10];
> >  };
> > diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
> > index 4d47b7c..fac3e2f 100644
> > --- a/drivers/usb/dwc2/gadget.c
> > +++ b/drivers/usb/dwc2/gadget.c
> > @@ -1954,6 +1954,7 @@ static void s3c_hsotg_epint(struct dwc2_hsotg
> *hsotg, unsigned int idx,
> >  		ints &= ~DXEPINT_XFERCOMPL;
> >
> >  	if (ints & DXEPINT_XFERCOMPL) {
> > +		hs_ep->has_correct_parity = 1;
> >  		if (hs_ep->isochronous && hs_ep->interval == 1) {
> >  			if (ctrl & DXEPCTL_EOFRNUM)
> >  				ctrl |= DXEPCTL_SETEVENFR;
> > @@ -2316,7 +2317,8 @@ void s3c_hsotg_core_init_disconnected(struct
> dwc2_hsotg *hsotg,
> >  		GINTSTS_CONIDSTSCHNG | GINTSTS_USBRST |
> >  		GINTSTS_RESETDET | GINTSTS_ENUMDONE |
> >  		GINTSTS_OTGINT | GINTSTS_USBSUSP |
> > -		GINTSTS_WKUPINT,
> > +		GINTSTS_WKUPINT |
> > +		GINTSTS_INCOMPL_SOIN | GINTSTS_INCOMPL_SOOUT,
> >  		hsotg->regs + GINTMSK);
> >
> >  	if (using_dma(hsotg))
> > @@ -2581,6 +2583,52 @@ irq_retry:
> >  		s3c_hsotg_dump(hsotg);
> >  	}
> >
> > +	if (gintsts & GINTSTS_INCOMPL_SOIN) {
> > +		u32 idx, epctl_reg, ctrl;
> > +		struct s3c_hsotg_ep *hs_ep;
> > +
> > +		dev_dbg(hsotg->dev, "%s: GINTSTS_INCOMPL_SOIN\n",
> __func__);
> > +		for (idx = 1; idx < MAX_EPS_CHANNELS; idx++) {
> 
> Valid endpoints are only up to hsotg->num_of_eps so this might crash on
> certain configurations.
> 
> Also, have you tried to find the endpoint which caused the incomplete
> interrupt by reading the control registers as described in the databook?
> 

We are using procedure based on description from this source:

Synopsys, Inc. SolvNet 527
DesignWare.com
3.00a
April 2012
USB 2.0 Hi-Speed On-The-Go (OTG) Databook Isochronous Endpoints in DWC_otg Slave Mode

Synopsys databook is not in a public domain to quote the exact paragraph here. You can find it in Chapter E, pp 526-527. There is no register in this databook, which would provide information about the source endpoint of the incomplete interrupt, as you have described.

Please, provide an exact reference and possibly enough information that we can turn it into a working code.

> > +			hs_ep = hsotg->eps_in[idx];
> > +
> > +			if (!hs_ep->isochronous || hs_ep-
> >has_correct_parity)
> > +				continue;
> > +
> > +			epctl_reg = DIEPCTL(idx);
> > +			ctrl = readl(hsotg->regs + epctl_reg);
> > +
> > +			if (ctrl & DXEPCTL_EOFRNUM)
> > +				ctrl |= DXEPCTL_SETEVENFR;
> > +			else
> > +				ctrl |= DXEPCTL_SETODDFR;
> > +			writel(ctrl, hsotg->regs + epctl_reg);
> 
> This toggling code could be moved out to a helper function to reduce
> redundancy as it is in three places now.
> 
> Regards,
> John

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