RE: [PATCH 1/1] usb: dwc2: gadget: parity fix in isochronous mode

[Roman Bacik]

> -----Original Message-----
> From: John Youn [mailto:John.Youn@xxxxxxxxxxxx]
> Sent: August-25-15 7:06 PM
> To: Roman Bacik; John Youn; Scott Branden; Greg Kroah-Hartman; linux-
> usb@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; bcm-kernel-feedback-list
> Subject: Re: [PATCH 1/1] usb: dwc2: gadget: parity fix in isochronous mode
> 
> On 8/25/2015 3:00 PM, Roman Bacik wrote:
> >> -----Original Message-----
> >> From: John Youn [mailto:John.Youn@xxxxxxxxxxxx]
> >> Sent: August-25-15 2:52 PM
> >> To: Scott Branden; John Youn; Greg Kroah-Hartman; linux-
> >> usb@xxxxxxxxxxxxxxx
> >> Cc: linux-kernel@xxxxxxxxxxxxxxx; bcm-kernel-feedback-list; Roman
> >> Bacik
> >> Subject: Re: [PATCH 1/1] usb: dwc2: gadget: parity fix in isochronous
> >> mode
> >>
> >> On 8/18/2015 8:45 AM, Scott Branden wrote:
> >>> From: Roman Bacik <rbacik@xxxxxxxxxxxx>
> >>>
> >>> 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@xxxxxxxxxxxx>
> >>> Reviewed-by: Abhinav Ratna <aratna@xxxxxxxxxxxx>
> >>> Reviewed-by: Srinath Mannam <srinath.mannam@xxxxxxxxxxxx>
> >>> Reviewed-by: Scott Branden <sbranden@xxxxxxxxxxxx>
> >>> Signed-off-by: Scott Branden <sbranden@xxxxxxxxxxxx>
> >>> ---
> >>>  drivers/usb/dwc2/core.h   |  1 +
> >>>  drivers/usb/dwc2/gadget.c | 48
> >> ++++++++++++++++++++++++++++++++++++++++++++++-
> >>>  drivers/usb/dwc2/hw.h     |  1 +
> >>>  3 files changed, 49 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h index
> >>> 0ed87620..954d1cd 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            parity_set:1;
> >>>
> >>>  	char                    name[10];
> >>>  };
> >>> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
> >>> index 4d47b7c..28e4393 100644
> >>> --- a/drivers/usb/dwc2/gadget.c
> >>> +++ b/drivers/usb/dwc2/gadget.c
> >>> @@ -1954,6 +1954,8 @@ static void s3c_hsotg_epint(struct dwc2_hsotg
> >> *hsotg, unsigned int idx,
> >>>  		ints &= ~DXEPINT_XFERCOMPL;
> >>>
> >>>  	if (ints & DXEPINT_XFERCOMPL) {
> >>> +		if (hs_ep->isochronous && !hs_ep->parity_set)
> >>> +			hs_ep->parity_set = 1;
> >>>  		if (hs_ep->isochronous && hs_ep->interval == 1) {
> >>>  			if (ctrl & DXEPCTL_EOFRNUM)
> >>>  				ctrl |= DXEPCTL_SETEVENFR;
> >>> @@ -2316,7 +2318,8 @@ 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 +2584,48 @@ irq_retry:
> >>>  		s3c_hsotg_dump(hsotg);
> >>>  	}
> >>>
> >>> +	if (gintsts & GINTSTS_INCOMPL_SOIN) {
> >>> +		u32 idx;
> >>> +		struct s3c_hsotg_ep *hs_ep;
> >>> +
> >>> +		dev_dbg(hsotg->dev, "%s: GINTSTS_INCOMPL_SOIN\n",
> >> __func__);
> >>> +		for (idx = 1; idx < MAX_EPS_CHANNELS; idx++) {
> >>> +			hs_ep = hsotg->eps_in[idx];
> >>> +			if (hs_ep->isochronous && !hs_ep->parity_set) {
> >>> +				u32 epctl_reg = DIEPCTL(idx);
> >>> +				u32 ctrl = readl(hsotg->regs + epctl_reg);
> >>> +
> >>> +				if (ctrl & DXEPCTL_EOFRNUM)
> >>> +					ctrl |= DXEPCTL_SETEVENFR;
> >>> +				else
> >>> +					ctrl |= DXEPCTL_SETODDFR;
> >>> +				writel(ctrl, hsotg->regs + epctl_reg);
> >>> +			}
> >>> +		}
> >>> +		writel(GINTSTS_INCOMPL_SOIN, hsotg->regs + GINTSTS);
> >>> +	}
> >>> +
> >>> +	if (gintsts & GINTSTS_INCOMPL_SOOUT) {
> >>> +		u32 idx;
> >>> +		struct s3c_hsotg_ep *hs_ep;
> >>> +
> >>> +		dev_dbg(hsotg->dev, "%s: GINTSTS_INCOMPL_SOOUT\n",
> >> __func__);
> >>> +		for (idx = 1; idx < MAX_EPS_CHANNELS; idx++) {
> >>> +			hs_ep = hsotg->eps_out[idx];
> >>> +			if (hs_ep->isochronous && !hs_ep->parity_set) {
> >>> +				u32 epctl_reg = DOEPCTL(idx);
> >>> +				u32 ctrl = readl(hsotg->regs + epctl_reg);
> >>> +
> >>> +				if (ctrl & DXEPCTL_EOFRNUM)
> >>> +					ctrl |= DXEPCTL_SETEVENFR;
> >>> +				else
> >>> +					ctrl |= DXEPCTL_SETODDFR;
> >>> +				writel(ctrl, hsotg->regs + epctl_reg);
> >>> +			}
> >>> +		}
> >>> +		writel(GINTSTS_INCOMPL_SOOUT, hsotg->regs + GINTSTS);
> >>> +	}
> >>> +
> >>>  	/*
> >>>  	 * if we've had fifo events, we should try and go around the
> >>>  	 * loop again to see if there's any point in returning yet.
> >>> @@ -2667,6 +2712,7 @@ static int s3c_hsotg_ep_enable(struct usb_ep
> >> *ep,
> >>>  	hs_ep->periodic = 0;
> >>>  	hs_ep->halted = 0;
> >>>  	hs_ep->interval = desc->bInterval;
> >>> +	hs_ep->parity_set = 0;
> >>
> >>
> >> I'm not quite sure what the parity_set flag does in this patch.
> >> Shouldn't you be able to just toggle the even/odd frame when you get
> >> the interrupt?
> >>
> >> John
> >>
> >
> > When Transfer Complete interrupt is received, we have the correct parity.
> Therefore we set the flag and we stop toggling. The parity_set flag indicates
> whether we have the correct parity set.
> > Regards,
> >
> > Roman
> >
> 
> I'm not sure that "parity" is the proper term in this context but I can't think of
> a more concise way to phrase it.
> 
> What if the host switches again some time after the first xfer complete?
> 
> What function or gadget driver are you using to test this? Did you test both
> the ISO IN and OUT case?
> 
> John
> 
> 

This patch is related to isochronous or periodic transfers. So server uses the same microframe number and hence parity for transfers. I tested both IN and OUT directions using audio gadget on Altera SocKit and Broadcom development boards.

Regards,

Roman
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