[PATCH v2 0/2] usb: dwc3: gadget: improve isoc handling

[PATCH v2 0/2] usb: dwc3: gadget: improve isoc handling

[Michael Grzeschik]

These two patches improve the isoc handling and make the dwc3 gadget
driver somewhat usable with the UVC gadget for isochronous endpoints.

The first patch makes starting isochronous transfers more reliable. I
think it's more less, what Thinh suggested some time ago[1]. It's still
not perfect because the first request must still be queued within 2
seconds but it's a lot better than the current situation.

The second patch makes it possible to have gaps in the data stream. The 
UVC gadget relies on such behaviour. Without this, using the UVC gadget
with a live stream stops after the first frame that needs more time to
be scheduled.

[1] https://marc.info/?l=linux-usb&m=156088170723824&w=4


Michael Grzeschik (1):
  usb: dwc3: gadget: when the started list is empty stop the active xfer

Michael Olbrich (1):
  usb: dwc3: gadget: make starting isoc transfers more robust

 drivers/usb/dwc3/gadget.c | 42 +++++++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 13 deletions(-)

-- 
2.27.0

[PATCH v2 1/2] usb: dwc3: gadget: make starting isoc transfers more robust

[Michael Grzeschik]

From: Michael Olbrich <m.olbrich@pengutronix.de>

Currently __dwc3_gadget_start_isoc must be called very shortly after
XferNotReady. Otherwise the frame number is outdated and start transfer
will fail, even with several retries.

DSTS provides the lower 14 bit of the frame number. Use it in combination
with the frame number provided by XferNotReady to guess the current frame
number. This will succeed unless more than one 14 rollover has happened
since XferNotReady.

Start transfer might still fail if the frame number is increased
immediately after DSTS is read. So retries are still needed.
Don't drop the current request if this happens. This way it is not lost and
can be used immediately to try again with the next frame number.

With this change, __dwc3_gadget_start_isoc is still not successfully in all
cases bit it increases the acceptable delay after XferNotReady
significantly.

Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

---
v1 -> v2: - removed last_frame_number from struct
          - included rollover variable

 drivers/usb/dwc3/gadget.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 421a0f73110a40b..0962ddd7fbf6ae6 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1276,7 +1276,7 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep)
 
 static void dwc3_gadget_ep_cleanup_cancelled_requests(struct dwc3_ep *dep);
 
-static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
+static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep, bool keep_req)
 {
 	struct dwc3_gadget_ep_cmd_params params;
 	struct dwc3_request		*req;
@@ -1314,12 +1314,9 @@ static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
 	}
 
 	ret = dwc3_send_gadget_ep_cmd(dep, cmd, &params);
-	if (ret < 0) {
+	if (ret < 0 && (!keep_req || ret != -EAGAIN)) {
 		struct dwc3_request *tmp;
 
-		if (ret == -EAGAIN)
-			return ret;
-
 		dwc3_stop_active_transfer(dep, true, true);
 
 		list_for_each_entry_safe(req, tmp, &dep->started_list, list)
@@ -1335,7 +1332,7 @@ static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
 	if (dep->stream_capable && req->request.is_last)
 		dep->flags |= DWC3_EP_WAIT_TRANSFER_COMPLETE;
 
-	return 0;
+	return ret;
 }
 
 static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
@@ -1458,7 +1455,7 @@ static int dwc3_gadget_start_isoc_quirk(struct dwc3_ep *dep)
 	dep->start_cmd_status = 0;
 	dep->combo_num = 0;
 
-	return __dwc3_gadget_kick_transfer(dep);
+	return __dwc3_gadget_kick_transfer(dep, false);
 }
 
 static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
@@ -1481,9 +1478,25 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
 	}
 
 	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
-		dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
+		/*
+		 * frame_number is set from XferNotReady and may be already
+		 * out of date. DSTS only provides the lower 14 bit of the
+		 * current frame number. So add the upper two bits of
+		 * frame_number and handle a possible rollover.
+		 * This will provide the correct frame_number unless more than
+		 * rollover has happened since XferNotReady.
+		 */
+		u32 frame = __dwc3_gadget_get_frame(dwc);
+		bool rollover = frame < (dep->frame_number & 0x3fff);
+
+		dep->frame_number = (dep->frame_number & ~0x3fff) | frame;
+		if (rollover)
+			dep->frame_number += BIT(14);
+
+		dep->frame_number = DWC3_ALIGN_FRAME(dep, 1);
 
-		ret = __dwc3_gadget_kick_transfer(dep);
+		ret = __dwc3_gadget_kick_transfer(dep,
+				i + 1 < DWC3_ISOC_MAX_RETRIES);
 		if (ret != -EAGAIN)
 			break;
 	}
@@ -1567,7 +1580,7 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
 		}
 	}
 
-	return __dwc3_gadget_kick_transfer(dep);
+	return __dwc3_gadget_kick_transfer(dep, false);
 }
 
 static int dwc3_gadget_ep_queue(struct usb_ep *ep, struct usb_request *request,
@@ -2719,7 +2732,7 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
 	if (status == -EXDEV && list_empty(&dep->started_list))
 		dwc3_stop_active_transfer(dep, true, true);
 	else if (dwc3_gadget_ep_should_continue(dep))
-		if (__dwc3_gadget_kick_transfer(dep) == 0)
+		if (__dwc3_gadget_kick_transfer(dep, false) == 0)
 			no_started_trb = false;
 
 out:
@@ -2904,7 +2917,7 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
 			dwc3_gadget_ep_cleanup_cancelled_requests(dep);
 			if ((dep->flags & DWC3_EP_DELAY_START) &&
 			    !usb_endpoint_xfer_isoc(dep->endpoint.desc))
-				__dwc3_gadget_kick_transfer(dep);
+				__dwc3_gadget_kick_transfer(dep, false);
 
 			dep->flags &= ~DWC3_EP_DELAY_START;
 		}
-- 
2.27.0

[PATCH v2 2/2] usb: dwc3: gadget: when the started list is empty stop the active xfer

[Michael Grzeschik]

When we have nothing left to be queued after handling the last trb
we have to stop the current transfer. This way we can ensure that
the next request will be queued with an new and valid timestamp
and will not directly run into an missed xfer.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

---
v1 -> v2: - This Patch replaces the following patch by Michael Olbrich:
            usb: dwc3: gadget: restart the transfer if a isoc request is queued too late

 drivers/usb/dwc3/gadget.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 0962ddd7fbf6ae6..b2b8b911ac79b39 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2729,7 +2729,10 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
 	if (dep->flags & DWC3_EP_END_TRANSFER_PENDING)
 		goto out;
 
-	if (status == -EXDEV && list_empty(&dep->started_list))
+	if ((status == -EXDEV && list_empty(&dep->started_list)) ||
+		(usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
+			list_empty(&dep->started_list) &&
+			list_empty(&dep->pending_list)))
 		dwc3_stop_active_transfer(dep, true, true);
 	else if (dwc3_gadget_ep_should_continue(dep))
 		if (__dwc3_gadget_kick_transfer(dep, false) == 0)
-- 
2.27.0

Re: [PATCH v2 1/2] usb: dwc3: gadget: make starting isoc transfers more robust

[Thinh Nguyen]

Hi,

Michael Grzeschik wrote:
> From: Michael Olbrich <m.olbrich@pengutronix.de>
>
> Currently __dwc3_gadget_start_isoc must be called very shortly after
> XferNotReady. Otherwise the frame number is outdated and start transfer
> will fail, even with several retries.

Did you try with the recent update for isoc? (e.i., after 5 
START_TRANSFER failures, the driver will issue END_TRANSFER to retry on 
the next XferNotReady event)

Let me know if you still run into issues with that.

>
> DSTS provides the lower 14 bit of the frame number. Use it in combination
> with the frame number provided by XferNotReady to guess the current frame
> number. This will succeed unless more than one 14 rollover has happened
> since XferNotReady.
>
> Start transfer might still fail if the frame number is increased
> immediately after DSTS is read. So retries are still needed.
> Don't drop the current request if this happens. This way it is not lost and
> can be used immediately to try again with the next frame number.
>
> With this change, __dwc3_gadget_start_isoc is still not successfully in all
> cases bit it increases the acceptable delay after XferNotReady
> significantly.
>
> Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>
> ---
> v1 -> v2: - removed last_frame_number from struct
>            - included rollover variable
>
>   drivers/usb/dwc3/gadget.c | 37 +++++++++++++++++++++++++------------
>   1 file changed, 25 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 421a0f73110a40b..0962ddd7fbf6ae6 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -1276,7 +1276,7 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep)
>   
>   static void dwc3_gadget_ep_cleanup_cancelled_requests(struct dwc3_ep *dep);
>   
> -static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
> +static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep, bool keep_req)

Any reason to have keep_req? With the recent changes, if 
dwc3_send_gadget_ep_cmd() returns -EAGAIN, then the controller driver 
won't give back the request.

>   {
>   	struct dwc3_gadget_ep_cmd_params params;
>   	struct dwc3_request		*req;
> @@ -1314,12 +1314,9 @@ static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>   	}
>   
>   	ret = dwc3_send_gadget_ep_cmd(dep, cmd, &params);
> -	if (ret < 0) {
> +	if (ret < 0 && (!keep_req || ret != -EAGAIN)) {
>   		struct dwc3_request *tmp;
>   
> -		if (ret == -EAGAIN)
> -			return ret;
> -
>   		dwc3_stop_active_transfer(dep, true, true);
>   
>   		list_for_each_entry_safe(req, tmp, &dep->started_list, list)
> @@ -1335,7 +1332,7 @@ static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>   	if (dep->stream_capable && req->request.is_last)
>   		dep->flags |= DWC3_EP_WAIT_TRANSFER_COMPLETE;
>   
> -	return 0;
> +	return ret;
>   }
>   
>   static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
> @@ -1458,7 +1455,7 @@ static int dwc3_gadget_start_isoc_quirk(struct dwc3_ep *dep)
>   	dep->start_cmd_status = 0;
>   	dep->combo_num = 0;
>   
> -	return __dwc3_gadget_kick_transfer(dep);
> +	return __dwc3_gadget_kick_transfer(dep, false);
>   }
>   
>   static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
> @@ -1481,9 +1478,25 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>   	}
>   
>   	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
> -		dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
> +		/*
> +		 * frame_number is set from XferNotReady and may be already
> +		 * out of date. DSTS only provides the lower 14 bit of the
> +		 * current frame number. So add the upper two bits of
> +		 * frame_number and handle a possible rollover.
> +		 * This will provide the correct frame_number unless more than
> +		 * rollover has happened since XferNotReady.
> +		 */
> +		u32 frame = __dwc3_gadget_get_frame(dwc);
> +		bool rollover = frame < (dep->frame_number & 0x3fff);
> +
> +		dep->frame_number = (dep->frame_number & ~0x3fff) | frame;
> +		if (rollover)
> +			dep->frame_number += BIT(14);
> +
> +		dep->frame_number = DWC3_ALIGN_FRAME(dep, 1);
>   
> -		ret = __dwc3_gadget_kick_transfer(dep);
> +		ret = __dwc3_gadget_kick_transfer(dep,
> +				i + 1 < DWC3_ISOC_MAX_RETRIES);
>   		if (ret != -EAGAIN)
>   			break;
>   	}
> @@ -1567,7 +1580,7 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
>   		}
>   	}
>   
> -	return __dwc3_gadget_kick_transfer(dep);
> +	return __dwc3_gadget_kick_transfer(dep, false);
>   }
>   
>   static int dwc3_gadget_ep_queue(struct usb_ep *ep, struct usb_request *request,
> @@ -2719,7 +2732,7 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
>   	if (status == -EXDEV && list_empty(&dep->started_list))
>   		dwc3_stop_active_transfer(dep, true, true);
>   	else if (dwc3_gadget_ep_should_continue(dep))
> -		if (__dwc3_gadget_kick_transfer(dep) == 0)
> +		if (__dwc3_gadget_kick_transfer(dep, false) == 0)
>   			no_started_trb = false;
>   
>   out:
> @@ -2904,7 +2917,7 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
>   			dwc3_gadget_ep_cleanup_cancelled_requests(dep);
>   			if ((dep->flags & DWC3_EP_DELAY_START) &&
>   			    !usb_endpoint_xfer_isoc(dep->endpoint.desc))
> -				__dwc3_gadget_kick_transfer(dep);
> +				__dwc3_gadget_kick_transfer(dep, false);
>   
>   			dep->flags &= ~DWC3_EP_DELAY_START;
>   		}

BR,
Thinh

Re: [PATCH v2 2/2] usb: dwc3: gadget: when the started list is empty stop the active xfer

[Thinh Nguyen]

Hi,

Michael Grzeschik wrote:
> When we have nothing left to be queued after handling the last trb
> we have to stop the current transfer. This way we can ensure that
> the next request will be queued with an new and valid timestamp
> and will not directly run into an missed xfer.
>
> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>
> ---
> v1 -> v2: - This Patch replaces the following patch by Michael Olbrich:
>              usb: dwc3: gadget: restart the transfer if a isoc request is queued too late
>
>   drivers/usb/dwc3/gadget.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 0962ddd7fbf6ae6..b2b8b911ac79b39 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2729,7 +2729,10 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
>   	if (dep->flags & DWC3_EP_END_TRANSFER_PENDING)
>   		goto out;
>   
> -	if (status == -EXDEV && list_empty(&dep->started_list))
> +	if ((status == -EXDEV && list_empty(&dep->started_list)) ||
> +		(usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
> +			list_empty(&dep->started_list) &&
> +			list_empty(&dep->pending_list)))

The -EXDEV check is also for isoc, maybe rearrange this for easier read:
if (usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
     list_empty(&dep->started_list) &&
     (list_empty(&dep->pending_list) || status == -EXDEV))

>   		dwc3_stop_active_transfer(dep, true, true);
>   	else if (dwc3_gadget_ep_should_continue(dep))
>   		if (__dwc3_gadget_kick_transfer(dep, false) == 0)

BR,
Thinh

Re: [PATCH v2 1/2] usb: dwc3: gadget: make starting isoc transfers more robust

[Thinh Nguyen]

Thinh Nguyen wrote:
> Hi,
>
> Michael Grzeschik wrote:
>> From: Michael Olbrich <m.olbrich@pengutronix.de>
>>
>> Currently __dwc3_gadget_start_isoc must be called very shortly after
>> XferNotReady. Otherwise the frame number is outdated and start transfer
>> will fail, even with several retries.
> Did you try with the recent update for isoc? (e.i., after 5
> START_TRANSFER failures, the driver will issue END_TRANSFER to retry on
> the next XferNotReady event)
>
> Let me know if you still run into issues with that.

Just want to clarify, I like this solution. I'm just curious how it 
behaves on your test setup with the current implementation.

>
>> DSTS provides the lower 14 bit of the frame number. Use it in combination
>> with the frame number provided by XferNotReady to guess the current frame
>> number. This will succeed unless more than one 14 rollover has happened
>> since XferNotReady.
>>
>> Start transfer might still fail if the frame number is increased
>> immediately after DSTS is read. So retries are still needed.
>> Don't drop the current request if this happens. This way it is not lost and
>> can be used immediately to try again with the next frame number.
>>
>> With this change, __dwc3_gadget_start_isoc is still not successfully in all
>> cases bit it increases the acceptable delay after XferNotReady
>> significantly.
>>
>> Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
>> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>>
>> ---
>> v1 -> v2: - removed last_frame_number from struct
>>             - included rollover variable
>>
>>    drivers/usb/dwc3/gadget.c | 37 +++++++++++++++++++++++++------------
>>    1 file changed, 25 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 421a0f73110a40b..0962ddd7fbf6ae6 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -1276,7 +1276,7 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep)
>>    
>>    static void dwc3_gadget_ep_cleanup_cancelled_requests(struct dwc3_ep *dep);
>>    
>> -static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>> +static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep, bool keep_req)
> Any reason to have keep_req? With the recent changes, if
> dwc3_send_gadget_ep_cmd() returns -EAGAIN, then the controller driver
> won't give back the request.
>

BR,
Thinh

Re: [PATCH v2 1/2] usb: dwc3: gadget: make starting isoc transfers more robust

[Michael Grzeschik]

[-- Attachment #1: Type: text/plain, Size: 6812 bytes --]

Hi!

On Wed, Jun 24, 2020 at 07:26:42PM +0000, Thinh Nguyen wrote:
>Michael Grzeschik wrote:
>> From: Michael Olbrich <m.olbrich@pengutronix.de>
>>
>> Currently __dwc3_gadget_start_isoc must be called very shortly after
>> XferNotReady. Otherwise the frame number is outdated and start transfer
>> will fail, even with several retries.
>
>Did you try with the recent update for isoc? (e.i., after 5
>START_TRANSFER failures, the driver will issue END_TRANSFER to retry on
>the next XferNotReady event)
>
>Let me know if you still run into issues with that.

Yes. Without my patch I still see the issue. Event with the retry
machanism. It is even worse. I even missed one additional patch,
I had on top this one. See my note below.

>> DSTS provides the lower 14 bit of the frame number. Use it in combination
>> with the frame number provided by XferNotReady to guess the current frame
>> number. This will succeed unless more than one 14 rollover has happened
>> since XferNotReady.
>>
>> Start transfer might still fail if the frame number is increased
>> immediately after DSTS is read. So retries are still needed.
>> Don't drop the current request if this happens. This way it is not lost and
>> can be used immediately to try again with the next frame number.
>>
>> With this change, __dwc3_gadget_start_isoc is still not successfully in all
>> cases bit it increases the acceptable delay after XferNotReady
>> significantly.
>>
>> Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
>> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>>
>> ---
>> v1 -> v2: - removed last_frame_number from struct
>>            - included rollover variable
>>
>>   drivers/usb/dwc3/gadget.c | 37 +++++++++++++++++++++++++------------
>>   1 file changed, 25 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 421a0f73110a40b..0962ddd7fbf6ae6 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -1276,7 +1276,7 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep)
>>
>>   static void dwc3_gadget_ep_cleanup_cancelled_requests(struct dwc3_ep *dep);
>>
>> -static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>> +static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep, bool keep_req)
>
>Any reason to have keep_req? With the recent changes, if
>dwc3_send_gadget_ep_cmd() returns -EAGAIN, then the controller driver
>won't give back the request.

Yes, we don't need the keep_req. I tried this and it worked without.
I will remove the parameter in v3.

>>   {
>>   	struct dwc3_gadget_ep_cmd_params params;
>>   	struct dwc3_request		*req;
>> @@ -1314,12 +1314,9 @@ static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>>   	}
>>
>>   	ret = dwc3_send_gadget_ep_cmd(dep, cmd, &params);
>> -	if (ret < 0) {
>> +	if (ret < 0 && (!keep_req || ret != -EAGAIN)) {
>>   		struct dwc3_request *tmp;
>>
>> -		if (ret == -EAGAIN)
>> -			return ret;
>> -
>>   		dwc3_stop_active_transfer(dep, true, true);
>>
>>   		list_for_each_entry_safe(req, tmp, &dep->started_list, list)
>> @@ -1335,7 +1332,7 @@ static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>>   	if (dep->stream_capable && req->request.is_last)
>>   		dep->flags |= DWC3_EP_WAIT_TRANSFER_COMPLETE;
>>
>> -	return 0;
>> +	return ret;
>>   }
>>
>>   static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
>> @@ -1458,7 +1455,7 @@ static int dwc3_gadget_start_isoc_quirk(struct dwc3_ep *dep)
>>   	dep->start_cmd_status = 0;
>>   	dep->combo_num = 0;
>>
>> -	return __dwc3_gadget_kick_transfer(dep);
>> +	return __dwc3_gadget_kick_transfer(dep, false);
>>   }
>>
>>   static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>> @@ -1481,9 +1478,25 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>>   	}
>>
>>   	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>> -		dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>> +		/*
>> +		 * frame_number is set from XferNotReady and may be already
>> +		 * out of date. DSTS only provides the lower 14 bit of the
>> +		 * current frame number. So add the upper two bits of
>> +		 * frame_number and handle a possible rollover.
>> +		 * This will provide the correct frame_number unless more than
>> +		 * rollover has happened since XferNotReady.
>> +		 */
>> +		u32 frame = __dwc3_gadget_get_frame(dwc);
>> +		bool rollover = frame < (dep->frame_number & 0x3fff);
>> +
>> +		dep->frame_number = (dep->frame_number & ~0x3fff) | frame;
>> +		if (rollover)
>> +			dep->frame_number += BIT(14);
>> +
>> +		dep->frame_number = DWC3_ALIGN_FRAME(dep, 1);

This is not enough, we have to add i into the alignment to ensure
that the stream is not failing:

                dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 2);

I am even thiking to move the frame number calculation into the
DWC3_DEPCMD_STARTTRANSFER code path of dwc3_send_gadget_ep_cmd. But this
will break the dwc3_gadget_start_isoc_quirk function. What do you think?

>>
>> -		ret = __dwc3_gadget_kick_transfer(dep);
>> +		ret = __dwc3_gadget_kick_transfer(dep,
>> +				i + 1 < DWC3_ISOC_MAX_RETRIES);
>>   		if (ret != -EAGAIN)
>>   			break;
>>   	}
>> @@ -1567,7 +1580,7 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
>>   		}
>>   	}
>>
>> -	return __dwc3_gadget_kick_transfer(dep);
>> +	return __dwc3_gadget_kick_transfer(dep, false);
>>   }
>>
>>   static int dwc3_gadget_ep_queue(struct usb_ep *ep, struct usb_request *request,
>> @@ -2719,7 +2732,7 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
>>   	if (status == -EXDEV && list_empty(&dep->started_list))
>>   		dwc3_stop_active_transfer(dep, true, true);
>>   	else if (dwc3_gadget_ep_should_continue(dep))
>> -		if (__dwc3_gadget_kick_transfer(dep) == 0)
>> +		if (__dwc3_gadget_kick_transfer(dep, false) == 0)
>>   			no_started_trb = false;
>>
>>   out:
>> @@ -2904,7 +2917,7 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
>>   			dwc3_gadget_ep_cleanup_cancelled_requests(dep);
>>   			if ((dep->flags & DWC3_EP_DELAY_START) &&
>>   			    !usb_endpoint_xfer_isoc(dep->endpoint.desc))
>> -				__dwc3_gadget_kick_transfer(dep);
>> +				__dwc3_gadget_kick_transfer(dep, false);
>>
>>   			dep->flags &= ~DWC3_EP_DELAY_START;
>>   		}

Thanks,
Michael

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
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Re: [PATCH v2 2/2] usb: dwc3: gadget: when the started list is empty stop the active xfer

[Michael Grzeschik]

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On Wed, Jun 24, 2020 at 07:43:44PM +0000, Thinh Nguyen wrote:
>Hi,
>
>Michael Grzeschik wrote:
>> When we have nothing left to be queued after handling the last trb
>> we have to stop the current transfer. This way we can ensure that
>> the next request will be queued with an new and valid timestamp
>> and will not directly run into an missed xfer.
>>
>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>>
>> ---
>> v1 -> v2: - This Patch replaces the following patch by Michael Olbrich:
>>              usb: dwc3: gadget: restart the transfer if a isoc request is queued too late
>>
>>   drivers/usb/dwc3/gadget.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 0962ddd7fbf6ae6..b2b8b911ac79b39 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2729,7 +2729,10 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
>>   	if (dep->flags & DWC3_EP_END_TRANSFER_PENDING)
>>   		goto out;
>>
>> -	if (status == -EXDEV && list_empty(&dep->started_list))
>> +	if ((status == -EXDEV && list_empty(&dep->started_list)) ||
>> +		(usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
>> +			list_empty(&dep->started_list) &&
>> +			list_empty(&dep->pending_list)))
>
>The -EXDEV check is also for isoc, maybe rearrange this for easier read:
>if (usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
>     list_empty(&dep->started_list) &&
>     (list_empty(&dep->pending_list) || status == -EXDEV))

Right, I will change it in v3.

>>   		dwc3_stop_active_transfer(dep, true, true);
>>   	else if (dwc3_gadget_ep_should_continue(dep))
>>   		if (__dwc3_gadget_kick_transfer(dep, false) == 0)

Thanks,
Michael

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [PATCH v2 1/2] usb: dwc3: gadget: make starting isoc transfers more robust

[Thinh Nguyen]

Hi,

Michael Grzeschik wrote:
> Hi!
>
> On Wed, Jun 24, 2020 at 07:26:42PM +0000, Thinh Nguyen wrote:
>> Michael Grzeschik wrote:
>>> From: Michael Olbrich <m.olbrich@pengutronix.de>
>>>
>>> Currently __dwc3_gadget_start_isoc must be called very shortly after
>>> XferNotReady. Otherwise the frame number is outdated and start transfer
>>> will fail, even with several retries.
>>
>> Did you try with the recent update for isoc? (e.i., after 5
>> START_TRANSFER failures, the driver will issue END_TRANSFER to retry on
>> the next XferNotReady event)
>>
>> Let me know if you still run into issues with that.
>
> Yes. Without my patch I still see the issue. Event with the retry
> machanism. It is even worse. I even missed one additional patch,
> I had on top this one. See my note below.

Ok. Can you clarify what issue you're seeing?

>
>>> DSTS provides the lower 14 bit of the frame number. Use it in 
>>> combination
>>> with the frame number provided by XferNotReady to guess the current 
>>> frame
>>> number. This will succeed unless more than one 14 rollover has happened
>>> since XferNotReady.
>>>
>>> Start transfer might still fail if the frame number is increased
>>> immediately after DSTS is read. So retries are still needed.
>>> Don't drop the current request if this happens. This way it is not 
>>> lost and
>>> can be used immediately to try again with the next frame number.
>>>
>>> With this change, __dwc3_gadget_start_isoc is still not successfully 
>>> in all
>>> cases bit it increases the acceptable delay after XferNotReady
>>> significantly.
>>>
>>> Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
>>> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
>>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>>>
>>> ---
>>> v1 -> v2: - removed last_frame_number from struct
>>>            - included rollover variable
>>>
>>>   drivers/usb/dwc3/gadget.c | 37 +++++++++++++++++++++++++------------
>>>   1 file changed, 25 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>> index 421a0f73110a40b..0962ddd7fbf6ae6 100644
>>> --- a/drivers/usb/dwc3/gadget.c
>>> +++ b/drivers/usb/dwc3/gadget.c
>>> @@ -1276,7 +1276,7 @@ static void dwc3_prepare_trbs(struct dwc3_ep 
>>> *dep)
>>>
>>>   static void dwc3_gadget_ep_cleanup_cancelled_requests(struct 
>>> dwc3_ep *dep);
>>>
>>> -static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>>> +static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep, bool 
>>> keep_req)
>>
>> Any reason to have keep_req? With the recent changes, if
>> dwc3_send_gadget_ep_cmd() returns -EAGAIN, then the controller driver
>> won't give back the request.
>
> Yes, we don't need the keep_req. I tried this and it worked without.
> I will remove the parameter in v3.
>
>>>   {
>>>       struct dwc3_gadget_ep_cmd_params params;
>>>       struct dwc3_request        *req;
>>> @@ -1314,12 +1314,9 @@ static int __dwc3_gadget_kick_transfer(struct 
>>> dwc3_ep *dep)
>>>       }
>>>
>>>       ret = dwc3_send_gadget_ep_cmd(dep, cmd, &params);
>>> -    if (ret < 0) {
>>> +    if (ret < 0 && (!keep_req || ret != -EAGAIN)) {
>>>           struct dwc3_request *tmp;
>>>
>>> -        if (ret == -EAGAIN)
>>> -            return ret;
>>> -
>>>           dwc3_stop_active_transfer(dep, true, true);
>>>
>>>           list_for_each_entry_safe(req, tmp, &dep->started_list, list)
>>> @@ -1335,7 +1332,7 @@ static int __dwc3_gadget_kick_transfer(struct 
>>> dwc3_ep *dep)
>>>       if (dep->stream_capable && req->request.is_last)
>>>           dep->flags |= DWC3_EP_WAIT_TRANSFER_COMPLETE;
>>>
>>> -    return 0;
>>> +    return ret;
>>>   }
>>>
>>>   static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
>>> @@ -1458,7 +1455,7 @@ static int dwc3_gadget_start_isoc_quirk(struct 
>>> dwc3_ep *dep)
>>>       dep->start_cmd_status = 0;
>>>       dep->combo_num = 0;
>>>
>>> -    return __dwc3_gadget_kick_transfer(dep);
>>> +    return __dwc3_gadget_kick_transfer(dep, false);
>>>   }
>>>
>>>   static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>>> @@ -1481,9 +1478,25 @@ static int __dwc3_gadget_start_isoc(struct 
>>> dwc3_ep *dep)
>>>       }
>>>
>>>       for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>>> -        dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>>> +        /*
>>> +         * frame_number is set from XferNotReady and may be already
>>> +         * out of date. DSTS only provides the lower 14 bit of the
>>> +         * current frame number. So add the upper two bits of
>>> +         * frame_number and handle a possible rollover.
>>> +         * This will provide the correct frame_number unless more than
>>> +         * rollover has happened since XferNotReady.
>>> +         */
>>> +        u32 frame = __dwc3_gadget_get_frame(dwc);
>>> +        bool rollover = frame < (dep->frame_number & 0x3fff);
>>> +
>>> +        dep->frame_number = (dep->frame_number & ~0x3fff) | frame;
>>> +        if (rollover)
>>> +            dep->frame_number += BIT(14);
>>> +
>>> +        dep->frame_number = DWC3_ALIGN_FRAME(dep, 1);
>
> This is not enough, we have to add i into the alignment to ensure
> that the stream is not failing:
>
>                dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 2);
>
> I am even thiking to move the frame number calculation into the
> DWC3_DEPCMD_STARTTRANSFER code path of dwc3_send_gadget_ep_cmd. But this
> will break the dwc3_gadget_start_isoc_quirk function. What do you think?

You shouldn't be keep calling __dwc3_gadget_get_frame() in a loop. You 
should do all these calculation to get the current frame_number only 
once before entering the retry loop.

The issue here is we don't know when the XferNotReady event will be 
handled, which may be too late and multiple uframe had gone by. But once 
the event is being handled, it shouldn't take much time at all. That 
means __dwc3_gadget_get_frame() will return the same value.

So, we need something like this:

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index f66ff7fd87a9..1cd73c2dbe71 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1709,6 +1709,8 @@ static int dwc3_gadget_start_isoc_quirk(struct 
dwc3_ep *dep)
  static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
  {
         struct dwc3 *dwc = dep->dwc;
+       u32 current_frame;
+       bool rollover;
         int ret;
         int i;

@@ -1725,6 +1727,13 @@ static int __dwc3_gadget_start_isoc(struct 
dwc3_ep *dep)
                         return dwc3_gadget_start_isoc_quirk(dep);
         }

+       current_frame = __dwc3_gadget_get_frame(dwc);
+       rollover = current_frame < (dep->frame_number & 0x3fff);
+
+        dep->frame_number = (dep->frame_number & ~0x3fff) | current_frame;
+        if (rollover)
+            dep->frame_number += BIT(14);
+
         for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
                 dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);


(Please create a macro for 0x3fff mask)

Thanks,
Thinh

Re: [PATCH v2 1/2] usb: dwc3: gadget: make starting isoc transfers more robust

[Thinh Nguyen]

Thinh Nguyen wrote:
> Hi,
>
> Michael Grzeschik wrote:
>> Hi!
>>
>> On Wed, Jun 24, 2020 at 07:26:42PM +0000, Thinh Nguyen wrote:
>>> Michael Grzeschik wrote:
>>>> From: Michael Olbrich <m.olbrich@pengutronix.de>
>>>>
>>>> Currently __dwc3_gadget_start_isoc must be called very shortly after
>>>> XferNotReady. Otherwise the frame number is outdated and start transfer
>>>> will fail, even with several retries.
>>> Did you try with the recent update for isoc? (e.i., after 5
>>> START_TRANSFER failures, the driver will issue END_TRANSFER to retry on
>>> the next XferNotReady event)
>>>
>>> Let me know if you still run into issues with that.
>> Yes. Without my patch I still see the issue. Event with the retry
>> machanism. It is even worse. I even missed one additional patch,
>> I had on top this one. See my note below.
> Ok. Can you clarify what issue you're seeing?
>
>>>> DSTS provides the lower 14 bit of the frame number. Use it in
>>>> combination
>>>> with the frame number provided by XferNotReady to guess the current
>>>> frame
>>>> number. This will succeed unless more than one 14 rollover has happened
>>>> since XferNotReady.
>>>>
>>>> Start transfer might still fail if the frame number is increased
>>>> immediately after DSTS is read. So retries are still needed.
>>>> Don't drop the current request if this happens. This way it is not
>>>> lost and
>>>> can be used immediately to try again with the next frame number.
>>>>
>>>> With this change, __dwc3_gadget_start_isoc is still not successfully
>>>> in all
>>>> cases bit it increases the acceptable delay after XferNotReady
>>>> significantly.
>>>>
>>>> Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
>>>> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
>>>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>>>>
>>>> ---
>>>> v1 -> v2: - removed last_frame_number from struct
>>>>             - included rollover variable
>>>>
>>>>    drivers/usb/dwc3/gadget.c | 37 +++++++++++++++++++++++++------------
>>>>    1 file changed, 25 insertions(+), 12 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>>> index 421a0f73110a40b..0962ddd7fbf6ae6 100644
>>>> --- a/drivers/usb/dwc3/gadget.c
>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>> @@ -1276,7 +1276,7 @@ static void dwc3_prepare_trbs(struct dwc3_ep
>>>> *dep)
>>>>
>>>>    static void dwc3_gadget_ep_cleanup_cancelled_requests(struct
>>>> dwc3_ep *dep);
>>>>
>>>> -static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>>>> +static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep, bool
>>>> keep_req)
>>> Any reason to have keep_req? With the recent changes, if
>>> dwc3_send_gadget_ep_cmd() returns -EAGAIN, then the controller driver
>>> won't give back the request.
>> Yes, we don't need the keep_req. I tried this and it worked without.
>> I will remove the parameter in v3.
>>
>>>>    {
>>>>        struct dwc3_gadget_ep_cmd_params params;
>>>>        struct dwc3_request        *req;
>>>> @@ -1314,12 +1314,9 @@ static int __dwc3_gadget_kick_transfer(struct
>>>> dwc3_ep *dep)
>>>>        }
>>>>
>>>>        ret = dwc3_send_gadget_ep_cmd(dep, cmd, &params);
>>>> -    if (ret < 0) {
>>>> +    if (ret < 0 && (!keep_req || ret != -EAGAIN)) {
>>>>            struct dwc3_request *tmp;
>>>>
>>>> -        if (ret == -EAGAIN)
>>>> -            return ret;
>>>> -
>>>>            dwc3_stop_active_transfer(dep, true, true);
>>>>
>>>>            list_for_each_entry_safe(req, tmp, &dep->started_list, list)
>>>> @@ -1335,7 +1332,7 @@ static int __dwc3_gadget_kick_transfer(struct
>>>> dwc3_ep *dep)
>>>>        if (dep->stream_capable && req->request.is_last)
>>>>            dep->flags |= DWC3_EP_WAIT_TRANSFER_COMPLETE;
>>>>
>>>> -    return 0;
>>>> +    return ret;
>>>>    }
>>>>
>>>>    static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
>>>> @@ -1458,7 +1455,7 @@ static int dwc3_gadget_start_isoc_quirk(struct
>>>> dwc3_ep *dep)
>>>>        dep->start_cmd_status = 0;
>>>>        dep->combo_num = 0;
>>>>
>>>> -    return __dwc3_gadget_kick_transfer(dep);
>>>> +    return __dwc3_gadget_kick_transfer(dep, false);
>>>>    }
>>>>
>>>>    static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>>>> @@ -1481,9 +1478,25 @@ static int __dwc3_gadget_start_isoc(struct
>>>> dwc3_ep *dep)
>>>>        }
>>>>
>>>>        for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>>>> -        dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>>>> +        /*
>>>> +         * frame_number is set from XferNotReady and may be already
>>>> +         * out of date. DSTS only provides the lower 14 bit of the
>>>> +         * current frame number. So add the upper two bits of
>>>> +         * frame_number and handle a possible rollover.
>>>> +         * This will provide the correct frame_number unless more than
>>>> +         * rollover has happened since XferNotReady.
>>>> +         */
>>>> +        u32 frame = __dwc3_gadget_get_frame(dwc);
>>>> +        bool rollover = frame < (dep->frame_number & 0x3fff);
>>>> +
>>>> +        dep->frame_number = (dep->frame_number & ~0x3fff) | frame;
>>>> +        if (rollover)
>>>> +            dep->frame_number += BIT(14);
>>>> +
>>>> +        dep->frame_number = DWC3_ALIGN_FRAME(dep, 1);
>> This is not enough, we have to add i into the alignment to ensure
>> that the stream is not failing:
>>
>>                 dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 2);
>>
>> I am even thiking to move the frame number calculation into the
>> DWC3_DEPCMD_STARTTRANSFER code path of dwc3_send_gadget_ep_cmd. But this
>> will break the dwc3_gadget_start_isoc_quirk function. What do you think?
> You shouldn't be keep calling __dwc3_gadget_get_frame() in a loop. You
> should do all these calculation to get the current frame_number only
> once before entering the retry loop.
>
> The issue here is we don't know when the XferNotReady event will be
> handled, which may be too late and multiple uframe had gone by. But once
> the event is being handled, it shouldn't take much time at all. That
> means __dwc3_gadget_get_frame() will return the same value.
>
> So, we need something like this:
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index f66ff7fd87a9..1cd73c2dbe71 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -1709,6 +1709,8 @@ static int dwc3_gadget_start_isoc_quirk(struct
> dwc3_ep *dep)
>    static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>    {
>           struct dwc3 *dwc = dep->dwc;
> +       u32 current_frame;
> +       bool rollover;
>           int ret;
>           int i;
>
> @@ -1725,6 +1727,13 @@ static int __dwc3_gadget_start_isoc(struct
> dwc3_ep *dep)
>                           return dwc3_gadget_start_isoc_quirk(dep);
>           }
>
> +       current_frame = __dwc3_gadget_get_frame(dwc);
> +       rollover = current_frame < (dep->frame_number & 0x3fff);
> +
> +        dep->frame_number = (dep->frame_number & ~0x3fff) | current_frame;
> +        if (rollover)
> +            dep->frame_number += BIT(14);
> +
>           for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>                   dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>
>
> (Please create a macro for 0x3fff mask)
>

Forgot a couple of notes:

1) If bInterval is greater than 14, don't attempt to get current frame 
from DSTS and ignore this mechanism.
2) The rollover check needs to account for number of uframes per 
interval. If the difference is less than an interval length, then no 
need to update dep->frame_number.

BR,
Thinh

Re: [PATCH v2 1/2] usb: dwc3: gadget: make starting isoc transfers more robust

[Thinh Nguyen]

Thinh Nguyen wrote:
> Thinh Nguyen wrote:
>> Hi,
>>
>> Michael Grzeschik wrote:
>>> Hi!
>>>
>>> On Wed, Jun 24, 2020 at 07:26:42PM +0000, Thinh Nguyen wrote:
>>>> Michael Grzeschik wrote:
>>>>> From: Michael Olbrich <m.olbrich@pengutronix.de>
>>>>>
>>>>> Currently __dwc3_gadget_start_isoc must be called very shortly after
>>>>> XferNotReady. Otherwise the frame number is outdated and start transfer
>>>>> will fail, even with several retries.
>>>> Did you try with the recent update for isoc? (e.i., after 5
>>>> START_TRANSFER failures, the driver will issue END_TRANSFER to retry on
>>>> the next XferNotReady event)
>>>>
>>>> Let me know if you still run into issues with that.
>>> Yes. Without my patch I still see the issue. Event with the retry
>>> machanism. It is even worse. I even missed one additional patch,
>>> I had on top this one. See my note below.
>> Ok. Can you clarify what issue you're seeing?
>>
>>>>> DSTS provides the lower 14 bit of the frame number. Use it in
>>>>> combination
>>>>> with the frame number provided by XferNotReady to guess the current
>>>>> frame
>>>>> number. This will succeed unless more than one 14 rollover has happened
>>>>> since XferNotReady.
>>>>>
>>>>> Start transfer might still fail if the frame number is increased
>>>>> immediately after DSTS is read. So retries are still needed.
>>>>> Don't drop the current request if this happens. This way it is not
>>>>> lost and
>>>>> can be used immediately to try again with the next frame number.
>>>>>
>>>>> With this change, __dwc3_gadget_start_isoc is still not successfully
>>>>> in all
>>>>> cases bit it increases the acceptable delay after XferNotReady
>>>>> significantly.
>>>>>
>>>>> Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
>>>>> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
>>>>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>>>>>
>>>>> ---
>>>>> v1 -> v2: - removed last_frame_number from struct
>>>>>              - included rollover variable
>>>>>
>>>>>     drivers/usb/dwc3/gadget.c | 37 +++++++++++++++++++++++++------------
>>>>>     1 file changed, 25 insertions(+), 12 deletions(-)
>>>>>
>>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>>>> index 421a0f73110a40b..0962ddd7fbf6ae6 100644
>>>>> --- a/drivers/usb/dwc3/gadget.c
>>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>>> @@ -1276,7 +1276,7 @@ static void dwc3_prepare_trbs(struct dwc3_ep
>>>>> *dep)
>>>>>
>>>>>     static void dwc3_gadget_ep_cleanup_cancelled_requests(struct
>>>>> dwc3_ep *dep);
>>>>>
>>>>> -static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>>>>> +static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep, bool
>>>>> keep_req)
>>>> Any reason to have keep_req? With the recent changes, if
>>>> dwc3_send_gadget_ep_cmd() returns -EAGAIN, then the controller driver
>>>> won't give back the request.
>>> Yes, we don't need the keep_req. I tried this and it worked without.
>>> I will remove the parameter in v3.
>>>
>>>>>     {
>>>>>         struct dwc3_gadget_ep_cmd_params params;
>>>>>         struct dwc3_request        *req;
>>>>> @@ -1314,12 +1314,9 @@ static int __dwc3_gadget_kick_transfer(struct
>>>>> dwc3_ep *dep)
>>>>>         }
>>>>>
>>>>>         ret = dwc3_send_gadget_ep_cmd(dep, cmd, &params);
>>>>> -    if (ret < 0) {
>>>>> +    if (ret < 0 && (!keep_req || ret != -EAGAIN)) {
>>>>>             struct dwc3_request *tmp;
>>>>>
>>>>> -        if (ret == -EAGAIN)
>>>>> -            return ret;
>>>>> -
>>>>>             dwc3_stop_active_transfer(dep, true, true);
>>>>>
>>>>>             list_for_each_entry_safe(req, tmp, &dep->started_list, list)
>>>>> @@ -1335,7 +1332,7 @@ static int __dwc3_gadget_kick_transfer(struct
>>>>> dwc3_ep *dep)
>>>>>         if (dep->stream_capable && req->request.is_last)
>>>>>             dep->flags |= DWC3_EP_WAIT_TRANSFER_COMPLETE;
>>>>>
>>>>> -    return 0;
>>>>> +    return ret;
>>>>>     }
>>>>>
>>>>>     static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
>>>>> @@ -1458,7 +1455,7 @@ static int dwc3_gadget_start_isoc_quirk(struct
>>>>> dwc3_ep *dep)
>>>>>         dep->start_cmd_status = 0;
>>>>>         dep->combo_num = 0;
>>>>>
>>>>> -    return __dwc3_gadget_kick_transfer(dep);
>>>>> +    return __dwc3_gadget_kick_transfer(dep, false);
>>>>>     }
>>>>>
>>>>>     static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>>>>> @@ -1481,9 +1478,25 @@ static int __dwc3_gadget_start_isoc(struct
>>>>> dwc3_ep *dep)
>>>>>         }
>>>>>
>>>>>         for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>>>>> -        dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>>>>> +        /*
>>>>> +         * frame_number is set from XferNotReady and may be already
>>>>> +         * out of date. DSTS only provides the lower 14 bit of the
>>>>> +         * current frame number. So add the upper two bits of
>>>>> +         * frame_number and handle a possible rollover.
>>>>> +         * This will provide the correct frame_number unless more than
>>>>> +         * rollover has happened since XferNotReady.
>>>>> +         */
>>>>> +        u32 frame = __dwc3_gadget_get_frame(dwc);
>>>>> +        bool rollover = frame < (dep->frame_number & 0x3fff);
>>>>> +
>>>>> +        dep->frame_number = (dep->frame_number & ~0x3fff) | frame;
>>>>> +        if (rollover)
>>>>> +            dep->frame_number += BIT(14);
>>>>> +
>>>>> +        dep->frame_number = DWC3_ALIGN_FRAME(dep, 1);
>>> This is not enough, we have to add i into the alignment to ensure
>>> that the stream is not failing:
>>>
>>>                  dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 2);
>>>
>>> I am even thiking to move the frame number calculation into the
>>> DWC3_DEPCMD_STARTTRANSFER code path of dwc3_send_gadget_ep_cmd. But this
>>> will break the dwc3_gadget_start_isoc_quirk function. What do you think?
>> You shouldn't be keep calling __dwc3_gadget_get_frame() in a loop. You
>> should do all these calculation to get the current frame_number only
>> once before entering the retry loop.
>>
>> The issue here is we don't know when the XferNotReady event will be
>> handled, which may be too late and multiple uframe had gone by. But once
>> the event is being handled, it shouldn't take much time at all. That
>> means __dwc3_gadget_get_frame() will return the same value.
>>
>> So, we need something like this:
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index f66ff7fd87a9..1cd73c2dbe71 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -1709,6 +1709,8 @@ static int dwc3_gadget_start_isoc_quirk(struct
>> dwc3_ep *dep)
>>     static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>>     {
>>            struct dwc3 *dwc = dep->dwc;
>> +       u32 current_frame;
>> +       bool rollover;
>>            int ret;
>>            int i;
>>
>> @@ -1725,6 +1727,13 @@ static int __dwc3_gadget_start_isoc(struct
>> dwc3_ep *dep)
>>                            return dwc3_gadget_start_isoc_quirk(dep);
>>            }
>>
>> +       current_frame = __dwc3_gadget_get_frame(dwc);
>> +       rollover = current_frame < (dep->frame_number & 0x3fff);
>> +
>> +        dep->frame_number = (dep->frame_number & ~0x3fff) | current_frame;
>> +        if (rollover)
>> +            dep->frame_number += BIT(14);
>> +
>>            for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>>                    dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>>
>>
>> (Please create a macro for 0x3fff mask)
>>
> Forgot a couple of notes:
>
> 1) If bInterval is greater than 14, don't attempt to get current frame
> from DSTS and ignore this mechanism.
> 2) The rollover check needs to account for number of uframes per
> interval. If the difference is less than an interval length, then no
> need to update dep->frame_number.
>

Ignore number 2), DWC3_ALIGN_FRAME() should take care of that...

BR,
Thinh

Re: [PATCH v2 1/2] usb: dwc3: gadget: make starting isoc transfers more robust

[Michael Grzeschik]

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On Thu, Jun 25, 2020 at 08:20:26PM +0000, Thinh Nguyen wrote:
>Thinh Nguyen wrote:
>> Thinh Nguyen wrote:
>>> Hi,
>>>
>>> Michael Grzeschik wrote:
>>>> Hi!
>>>>
>>>> On Wed, Jun 24, 2020 at 07:26:42PM +0000, Thinh Nguyen wrote:
>>>>> Michael Grzeschik wrote:
>>>>>> From: Michael Olbrich <m.olbrich@pengutronix.de>
>>>>>>
>>>>>> Currently __dwc3_gadget_start_isoc must be called very shortly after
>>>>>> XferNotReady. Otherwise the frame number is outdated and start transfer
>>>>>> will fail, even with several retries.
>>>>> Did you try with the recent update for isoc? (e.i., after 5
>>>>> START_TRANSFER failures, the driver will issue END_TRANSFER to retry on
>>>>> the next XferNotReady event)
>>>>>
>>>>> Let me know if you still run into issues with that.
>>>> Yes. Without my patch I still see the issue. Event with the retry
>>>> machanism. It is even worse. I even missed one additional patch,
>>>> I had on top this one. See my note below.
>>> Ok. Can you clarify what issue you're seeing?

Yes. There are many missed xfer events, flooding the uvc gadget
function driver.

>>>>>> DSTS provides the lower 14 bit of the frame number. Use it in
>>>>>> combination
>>>>>> with the frame number provided by XferNotReady to guess the current
>>>>>> frame
>>>>>> number. This will succeed unless more than one 14 rollover has happened
>>>>>> since XferNotReady.
>>>>>>
>>>>>> Start transfer might still fail if the frame number is increased
>>>>>> immediately after DSTS is read. So retries are still needed.
>>>>>> Don't drop the current request if this happens. This way it is not
>>>>>> lost and
>>>>>> can be used immediately to try again with the next frame number.
>>>>>>
>>>>>> With this change, __dwc3_gadget_start_isoc is still not successfully
>>>>>> in all
>>>>>> cases bit it increases the acceptable delay after XferNotReady
>>>>>> significantly.
>>>>>>
>>>>>> Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
>>>>>> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
>>>>>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>>>>>>
>>>>>> ---
>>>>>> v1 -> v2: - removed last_frame_number from struct
>>>>>>              - included rollover variable
>>>>>>
>>>>>>     drivers/usb/dwc3/gadget.c | 37 +++++++++++++++++++++++++------------
>>>>>>     1 file changed, 25 insertions(+), 12 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>>>>> index 421a0f73110a40b..0962ddd7fbf6ae6 100644
>>>>>> --- a/drivers/usb/dwc3/gadget.c
>>>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>>>> @@ -1276,7 +1276,7 @@ static void dwc3_prepare_trbs(struct dwc3_ep
>>>>>> *dep)
>>>>>>
>>>>>>     static void dwc3_gadget_ep_cleanup_cancelled_requests(struct
>>>>>> dwc3_ep *dep);
>>>>>>
>>>>>> -static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>>>>>> +static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep, bool
>>>>>> keep_req)
>>>>> Any reason to have keep_req? With the recent changes, if
>>>>> dwc3_send_gadget_ep_cmd() returns -EAGAIN, then the controller driver
>>>>> won't give back the request.
>>>> Yes, we don't need the keep_req. I tried this and it worked without.
>>>> I will remove the parameter in v3.
>>>>
>>>>>>     {
>>>>>>         struct dwc3_gadget_ep_cmd_params params;
>>>>>>         struct dwc3_request        *req;
>>>>>> @@ -1314,12 +1314,9 @@ static int __dwc3_gadget_kick_transfer(struct
>>>>>> dwc3_ep *dep)
>>>>>>         }
>>>>>>
>>>>>>         ret = dwc3_send_gadget_ep_cmd(dep, cmd, &params);
>>>>>> -    if (ret < 0) {
>>>>>> +    if (ret < 0 && (!keep_req || ret != -EAGAIN)) {
>>>>>>             struct dwc3_request *tmp;
>>>>>>
>>>>>> -        if (ret == -EAGAIN)
>>>>>> -            return ret;
>>>>>> -
>>>>>>             dwc3_stop_active_transfer(dep, true, true);
>>>>>>
>>>>>>             list_for_each_entry_safe(req, tmp, &dep->started_list, list)
>>>>>> @@ -1335,7 +1332,7 @@ static int __dwc3_gadget_kick_transfer(struct
>>>>>> dwc3_ep *dep)
>>>>>>         if (dep->stream_capable && req->request.is_last)
>>>>>>             dep->flags |= DWC3_EP_WAIT_TRANSFER_COMPLETE;
>>>>>>
>>>>>> -    return 0;
>>>>>> +    return ret;
>>>>>>     }
>>>>>>
>>>>>>     static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
>>>>>> @@ -1458,7 +1455,7 @@ static int dwc3_gadget_start_isoc_quirk(struct
>>>>>> dwc3_ep *dep)
>>>>>>         dep->start_cmd_status = 0;
>>>>>>         dep->combo_num = 0;
>>>>>>
>>>>>> -    return __dwc3_gadget_kick_transfer(dep);
>>>>>> +    return __dwc3_gadget_kick_transfer(dep, false);
>>>>>>     }
>>>>>>
>>>>>>     static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>>>>>> @@ -1481,9 +1478,25 @@ static int __dwc3_gadget_start_isoc(struct
>>>>>> dwc3_ep *dep)
>>>>>>         }
>>>>>>
>>>>>>         for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>>>>>> -        dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>>>>>> +        /*
>>>>>> +         * frame_number is set from XferNotReady and may be already
>>>>>> +         * out of date. DSTS only provides the lower 14 bit of the
>>>>>> +         * current frame number. So add the upper two bits of
>>>>>> +         * frame_number and handle a possible rollover.
>>>>>> +         * This will provide the correct frame_number unless more than
>>>>>> +         * rollover has happened since XferNotReady.
>>>>>> +         */
>>>>>> +        u32 frame = __dwc3_gadget_get_frame(dwc);
>>>>>> +        bool rollover = frame < (dep->frame_number & 0x3fff);
>>>>>> +
>>>>>> +        dep->frame_number = (dep->frame_number & ~0x3fff) | frame;
>>>>>> +        if (rollover)
>>>>>> +            dep->frame_number += BIT(14);
>>>>>> +
>>>>>> +        dep->frame_number = DWC3_ALIGN_FRAME(dep, 1);
>>>> This is not enough, we have to add i into the alignment to ensure
>>>> that the stream is not failing:
>>>>
>>>>                  dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 2);
>>>>
>>>> I am even thiking to move the frame number calculation into the
>>>> DWC3_DEPCMD_STARTTRANSFER code path of dwc3_send_gadget_ep_cmd. But this
>>>> will break the dwc3_gadget_start_isoc_quirk function. What do you think?
>>> You shouldn't be keep calling __dwc3_gadget_get_frame() in a loop. You
>>> should do all these calculation to get the current frame_number only
>>> once before entering the retry loop.
>>>
>>> The issue here is we don't know when the XferNotReady event will be
>>> handled, which may be too late and multiple uframe had gone by. But once
>>> the event is being handled, it shouldn't take much time at all. That
>>> means __dwc3_gadget_get_frame() will return the same value.
>>>
>>> So, we need something like this:
>>>
>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>> index f66ff7fd87a9..1cd73c2dbe71 100644
>>> --- a/drivers/usb/dwc3/gadget.c
>>> +++ b/drivers/usb/dwc3/gadget.c
>>> @@ -1709,6 +1709,8 @@ static int dwc3_gadget_start_isoc_quirk(struct
>>> dwc3_ep *dep)
>>>     static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>>>     {
>>>            struct dwc3 *dwc = dep->dwc;
>>> +       u32 current_frame;
>>> +       bool rollover;
>>>            int ret;
>>>            int i;
>>>
>>> @@ -1725,6 +1727,13 @@ static int __dwc3_gadget_start_isoc(struct
>>> dwc3_ep *dep)
>>>                            return dwc3_gadget_start_isoc_quirk(dep);
>>>            }
>>>
>>> +       current_frame = __dwc3_gadget_get_frame(dwc);
>>> +       rollover = current_frame < (dep->frame_number & 0x3fff);
>>> +
>>> +        dep->frame_number = (dep->frame_number & ~0x3fff) | current_frame;
>>> +        if (rollover)
>>> +            dep->frame_number += BIT(14);
>>> +
>>>            for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>>>                    dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>>>
>>>
>>> (Please create a macro for 0x3fff mask)
>>>
>> Forgot a couple of notes:
>>
>> 1) If bInterval is greater than 14, don't attempt to get current frame
>> from DSTS and ignore this mechanism.
>> 2) The rollover check needs to account for number of uframes per
>> interval. If the difference is less than an interval length, then no
>> need to update dep->frame_number.
>>
>
>Ignore number 2), DWC3_ALIGN_FRAME() should take care of that...

All right, I added the following changes to v3 before running
the retry loop.

        if (desc->bInterval <= 14) {
                u32 current_frame = __dwc3_gadget_get_frame(dwc);
                bool rollover = current_frame < (dep->frame_number & 0x3fff);

                dep->frame_number = (dep->frame_number & ~0x3fff) | current_frame;
                if (rollover)
                dep->frame_number += BIT(14);
                        dep->frame_number += BIT(14);
        }

Regards,
Michael

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