Re: [PATCH v2 1/1] usb: dwc2: gadget: parity fix in isochronous mode

[John Youn]

On 9/9/2015 11:16 AM, Roman Bacik wrote:
>> -----Original Message-----
>> From: John Youn [mailto:John.Youn@xxxxxxxxxxxx]
>> Sent: September-03-15 11:53 PM
>> To: Scott Branden; John Youn; Greg Kroah-Hartman; linux-
>> usb@xxxxxxxxxxxxxxx; Roman Bacik
>> Cc: linux-kernel@xxxxxxxxxxxxxxx; 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@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>
>>> Signed-off-by: Scott Branden <sbranden@xxxxxxxxxxxx>
>>> ---
>>>  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.
> 

You can check the source of the interrupt by reading the DSTS and
ep control registers as described in the databook page 526, last
bullet, and 527 first bullet.

John









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