[PATCH v2] usb: gadget: musb: fix short isoc packets with inventra dma

[PATCH v2] usb: gadget: musb: fix short isoc packets with inventra dma

[Paul Elder]

Handling short packets (length < max packet size) in the Inventra DMA
engine in the MUSB driver causes the MUSB DMA controller to hang. An
example of a problem that is caused by this problem is when streaming
video out of a UVC gadget, only the first video frame is transferred.

For short packets (mode-0 or mode-1 DMA), MUSB_TXCSR_TXPKTRDY must be
set manually by the driver. This was previously done in musb_g_tx
(musb_gadget.c), but incorrectly (all csr flags were cleared, and only
MUSB_TXCSR_MODE and MUSB_TXCSR_TXPKTRDY were set). Fixing that problem
allows some requests to be transferred correctly, but multiple requests
were often put together in one USB packet, and caused problems if the
packet size was not a multiple of 4. Instead, set MUSB_TXCSR_TXPKTRDY
in dma_controller_irq (musbhsdma.c), just like host mode transfers.

This topic was originally tackled by Nicolas Boichat [0] [1] and is
discussed further at [2] as part of his GSoC project [3].

[0] https://groups.google.com/forum/?hl=en#!topic/beagleboard-gsoc/k8Azwfp75CU
[1] https://gitorious.org/beagleboard-usbsniffer/beagleboard-usbsniffer-kernel/commit/b0be3b6cc195ba732189b04f1d43ec843c3e54c9?p=beagleboard-usbsniffer:beagleboard-usbsniffer-kernel.git;a=patch;h=b0be3b6cc195ba732189b04f1d43ec843c3e54c9
[2] http://beagleboard-usbsniffer.blogspot.com/2010/07/musb-isochronous-transfers-fixed.html
[3] http://elinux.org/BeagleBoard/GSoC/USBSniffer

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
---
Changes in v2:

- no more flushing FIFO
- greatly simplified short packet if guard in musb_g_tx, and removed
  unnecessary variables
- minor indentation and wording changes

 drivers/usb/musb/musb_gadget.c | 19 +++++--------------
 drivers/usb/musb/musbhsdma.c   | 21 +++++++++++----------
 2 files changed, 16 insertions(+), 24 deletions(-)

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index eae8b1b1b45b..496643f54faa 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -452,13 +452,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
 	}
 
 	if (request) {
-		u8	is_dma = 0;
-		bool	short_packet = false;
 
 		trace_musb_req_tx(req);
 
 		if (dma && (csr & MUSB_TXCSR_DMAENAB)) {
-			is_dma = 1;
 			csr |= MUSB_TXCSR_P_WZC_BITS;
 			csr &= ~(MUSB_TXCSR_DMAENAB | MUSB_TXCSR_P_UNDERRUN |
 				 MUSB_TXCSR_TXPKTRDY | MUSB_TXCSR_AUTOSET);
@@ -476,16 +473,8 @@ void musb_g_tx(struct musb *musb, u8 epnum)
 		 */
 		if ((request->zero && request->length)
 			&& (request->length % musb_ep->packet_sz == 0)
-			&& (request->actual == request->length))
-				short_packet = true;
+			&& (request->actual == request->length)) {
 
-		if ((musb_dma_inventra(musb) || musb_dma_ux500(musb)) &&
-			(is_dma && (!dma->desired_mode ||
-				(request->actual &
-					(musb_ep->packet_sz - 1)))))
-				short_packet = true;
-
-		if (short_packet) {
 			/*
 			 * On DMA completion, FIFO may not be
 			 * available yet...
@@ -493,8 +482,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
 			if (csr & MUSB_TXCSR_TXPKTRDY)
 				return;
 
-			musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE
-					| MUSB_TXCSR_TXPKTRDY);
+			musb_dbg(musb, "sending short pkt (zero=%d, length=%d, actual=%d, dma->desired_mode=%d)\n",
+				 request->zero, request->length, request->actual,
+				 dma->desired_mode);
+			musb_writew(epio, MUSB_TXCSR, csr | MUSB_TXCSR_TXPKTRDY);
 			request->zero = 0;
 		}
 
diff --git a/drivers/usb/musb/musbhsdma.c b/drivers/usb/musb/musbhsdma.c
index a688f7f87829..5fc6825745f2 100644
--- a/drivers/usb/musb/musbhsdma.c
+++ b/drivers/usb/musb/musbhsdma.c
@@ -346,12 +346,10 @@ static irqreturn_t dma_controller_irq(int irq, void *private_data)
 				channel->status = MUSB_DMA_STATUS_FREE;
 
 				/* completed */
-				if ((devctl & MUSB_DEVCTL_HM)
-					&& (musb_channel->transmit)
-					&& ((channel->desired_mode == 0)
-					    || (channel->actual_len &
-					    (musb_channel->max_packet_sz - 1)))
-				    ) {
+				if (musb_channel->transmit &&
+					(!channel->desired_mode ||
+					(channel->actual_len %
+					    musb_channel->max_packet_sz))) {
 					u8  epnum  = musb_channel->epnum;
 					int offset = musb->io.ep_offset(epnum,
 								    MUSB_TXCSR);
@@ -363,11 +361,14 @@ static irqreturn_t dma_controller_irq(int irq, void *private_data)
 					 */
 					musb_ep_select(mbase, epnum);
 					txcsr = musb_readw(mbase, offset);
-					txcsr &= ~(MUSB_TXCSR_DMAENAB
+					if (channel->desired_mode == 1) {
+						txcsr &= ~(MUSB_TXCSR_DMAENAB
 							| MUSB_TXCSR_AUTOSET);
-					musb_writew(mbase, offset, txcsr);
-					/* Send out the packet */
-					txcsr &= ~MUSB_TXCSR_DMAMODE;
+						musb_writew(mbase, offset, txcsr);
+						/* Send out the packet */
+						txcsr &= ~MUSB_TXCSR_DMAMODE;
+						txcsr |= MUSB_TXCSR_DMAENAB;
+					}
 					txcsr |=  MUSB_TXCSR_TXPKTRDY;
 					musb_writew(mbase, offset, txcsr);
 				}
-- 
2.20.1

Re: [PATCH v2] usb: gadget: musb: fix short isoc packets with inventra dma

[Bin Liu]

Hi Paul,

On Wed, Jan 09, 2019 at 02:10:09AM -0500, Paul Elder wrote:
> Handling short packets (length < max packet size) in the Inventra DMA
> engine in the MUSB driver causes the MUSB DMA controller to hang. An
> example of a problem that is caused by this problem is when streaming
> video out of a UVC gadget, only the first video frame is transferred.
> 
> For short packets (mode-0 or mode-1 DMA), MUSB_TXCSR_TXPKTRDY must be
> set manually by the driver. This was previously done in musb_g_tx
> (musb_gadget.c), but incorrectly (all csr flags were cleared, and only
> MUSB_TXCSR_MODE and MUSB_TXCSR_TXPKTRDY were set). Fixing that problem
> allows some requests to be transferred correctly, but multiple requests
> were often put together in one USB packet, and caused problems if the
> packet size was not a multiple of 4. Instead, set MUSB_TXCSR_TXPKTRDY
> in dma_controller_irq (musbhsdma.c), just like host mode transfers.
> 
> This topic was originally tackled by Nicolas Boichat [0] [1] and is
> discussed further at [2] as part of his GSoC project [3].
> 
> [0] https://groups.google.com/forum/?hl=en#!topic/beagleboard-gsoc/k8Azwfp75CU
> [1] https://gitorious.org/beagleboard-usbsniffer/beagleboard-usbsniffer-kernel/commit/b0be3b6cc195ba732189b04f1d43ec843c3e54c9?p=beagleboard-usbsniffer:beagleboard-usbsniffer-kernel.git;a=patch;h=b0be3b6cc195ba732189b04f1d43ec843c3e54c9
> [2] http://beagleboard-usbsniffer.blogspot.com/2010/07/musb-isochronous-transfers-fixed.html
> [3] http://elinux.org/BeagleBoard/GSoC/USBSniffer
> 
> Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
> ---
> Changes in v2:
> 
> - no more flushing FIFO
> - greatly simplified short packet if guard in musb_g_tx, and removed
>   unnecessary variables
> - minor indentation and wording changes
> 
>  drivers/usb/musb/musb_gadget.c | 19 +++++--------------
>  drivers/usb/musb/musbhsdma.c   | 21 +++++++++++----------
>  2 files changed, 16 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
> index eae8b1b1b45b..496643f54faa 100644
> --- a/drivers/usb/musb/musb_gadget.c
> +++ b/drivers/usb/musb/musb_gadget.c
> @@ -452,13 +452,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
>  	}
>  
>  	if (request) {
> -		u8	is_dma = 0;
> -		bool	short_packet = false;
>  
>  		trace_musb_req_tx(req);
>  
>  		if (dma && (csr & MUSB_TXCSR_DMAENAB)) {
> -			is_dma = 1;
>  			csr |= MUSB_TXCSR_P_WZC_BITS;
>  			csr &= ~(MUSB_TXCSR_DMAENAB | MUSB_TXCSR_P_UNDERRUN |
>  				 MUSB_TXCSR_TXPKTRDY | MUSB_TXCSR_AUTOSET);
> @@ -476,16 +473,8 @@ void musb_g_tx(struct musb *musb, u8 epnum)
>  		 */
>  		if ((request->zero && request->length)
>  			&& (request->length % musb_ep->packet_sz == 0)
> -			&& (request->actual == request->length))
> -				short_packet = true;
> +			&& (request->actual == request->length)) {
>  
> -		if ((musb_dma_inventra(musb) || musb_dma_ux500(musb)) &&
> -			(is_dma && (!dma->desired_mode ||
> -				(request->actual &
> -					(musb_ep->packet_sz - 1)))))
> -				short_packet = true;
> -
> -		if (short_packet) {
>  			/*
>  			 * On DMA completion, FIFO may not be
>  			 * available yet...
> @@ -493,8 +482,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
>  			if (csr & MUSB_TXCSR_TXPKTRDY)
>  				return;
>  
> -			musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE
> -					| MUSB_TXCSR_TXPKTRDY);
> +			musb_dbg(musb, "sending short pkt (zero=%d, length=%d, actual=%d, dma->desired_mode=%d)\n",
> +				 request->zero, request->length, request->actual,
> +				 dma->desired_mode);
> +			musb_writew(epio, MUSB_TXCSR, csr | MUSB_TXCSR_TXPKTRDY);

Sorry I didn't catch this in the last review, but this change seems not
required, isn't it? In the first version of the patch, the code is
'returned' in the 'if (musb_dma_inventra())' branch above, doesn't reach
here.

Regards,
-Bin.

Re: [PATCH v2] usb: gadget: musb: fix short isoc packets with inventra dma

[Paul Elder]

Hi Bin,

On Wed, Jan 09, 2019 at 09:02:15AM -0600, Bin Liu wrote:
> Hi Paul,
> 
> On Wed, Jan 09, 2019 at 02:10:09AM -0500, Paul Elder wrote:
> > Handling short packets (length < max packet size) in the Inventra DMA
> > engine in the MUSB driver causes the MUSB DMA controller to hang. An
> > example of a problem that is caused by this problem is when streaming
> > video out of a UVC gadget, only the first video frame is transferred.
> > 
> > For short packets (mode-0 or mode-1 DMA), MUSB_TXCSR_TXPKTRDY must be
> > set manually by the driver. This was previously done in musb_g_tx
> > (musb_gadget.c), but incorrectly (all csr flags were cleared, and only
> > MUSB_TXCSR_MODE and MUSB_TXCSR_TXPKTRDY were set). Fixing that problem
> > allows some requests to be transferred correctly, but multiple requests
> > were often put together in one USB packet, and caused problems if the
> > packet size was not a multiple of 4. Instead, set MUSB_TXCSR_TXPKTRDY
> > in dma_controller_irq (musbhsdma.c), just like host mode transfers.
> > 
> > This topic was originally tackled by Nicolas Boichat [0] [1] and is
> > discussed further at [2] as part of his GSoC project [3].
> > 
> > [0] https://groups.google.com/forum/?hl=en#!topic/beagleboard-gsoc/k8Azwfp75CU
> > [1] https://gitorious.org/beagleboard-usbsniffer/beagleboard-usbsniffer-kernel/commit/b0be3b6cc195ba732189b04f1d43ec843c3e54c9?p=beagleboard-usbsniffer:beagleboard-usbsniffer-kernel.git;a=patch;h=b0be3b6cc195ba732189b04f1d43ec843c3e54c9
> > [2] http://beagleboard-usbsniffer.blogspot.com/2010/07/musb-isochronous-transfers-fixed.html
> > [3] http://elinux.org/BeagleBoard/GSoC/USBSniffer
> > 
> > Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
> > ---
> > Changes in v2:
> > 
> > - no more flushing FIFO
> > - greatly simplified short packet if guard in musb_g_tx, and removed
> >   unnecessary variables
> > - minor indentation and wording changes
> > 
> >  drivers/usb/musb/musb_gadget.c | 19 +++++--------------
> >  drivers/usb/musb/musbhsdma.c   | 21 +++++++++++----------
> >  2 files changed, 16 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
> > index eae8b1b1b45b..496643f54faa 100644
> > --- a/drivers/usb/musb/musb_gadget.c
> > +++ b/drivers/usb/musb/musb_gadget.c
> > @@ -452,13 +452,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
> >  	}
> >  
> >  	if (request) {
> > -		u8	is_dma = 0;
> > -		bool	short_packet = false;
> >  
> >  		trace_musb_req_tx(req);
> >  
> >  		if (dma && (csr & MUSB_TXCSR_DMAENAB)) {
> > -			is_dma = 1;
> >  			csr |= MUSB_TXCSR_P_WZC_BITS;
> >  			csr &= ~(MUSB_TXCSR_DMAENAB | MUSB_TXCSR_P_UNDERRUN |
> >  				 MUSB_TXCSR_TXPKTRDY | MUSB_TXCSR_AUTOSET);
> > @@ -476,16 +473,8 @@ void musb_g_tx(struct musb *musb, u8 epnum)
> >  		 */
> >  		if ((request->zero && request->length)
> >  			&& (request->length % musb_ep->packet_sz == 0)
> > -			&& (request->actual == request->length))
> > -				short_packet = true;
> > +			&& (request->actual == request->length)) {
> >  
> > -		if ((musb_dma_inventra(musb) || musb_dma_ux500(musb)) &&
> > -			(is_dma && (!dma->desired_mode ||
> > -				(request->actual &
> > -					(musb_ep->packet_sz - 1)))))
> > -				short_packet = true;
> > -
> > -		if (short_packet) {
> >  			/*
> >  			 * On DMA completion, FIFO may not be
> >  			 * available yet...
> > @@ -493,8 +482,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
> >  			if (csr & MUSB_TXCSR_TXPKTRDY)
> >  				return;
> >  
> > -			musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE
> > -					| MUSB_TXCSR_TXPKTRDY);
> > +			musb_dbg(musb, "sending short pkt (zero=%d, length=%d, actual=%d, dma->desired_mode=%d)\n",
> > +				 request->zero, request->length, request->actual,
> > +				 dma->desired_mode);
> > +			musb_writew(epio, MUSB_TXCSR, csr | MUSB_TXCSR_TXPKTRDY);
> 
> Sorry I didn't catch this in the last review, but this change seems not
> required, isn't it? In the first version of the patch, the code is
> 'returned' in the 'if (musb_dma_inventra())' branch above, doesn't reach
> here.

Do you mean change compared to the last version of the patch, or this
last chunk of the diff?

I guess I did also remove the return when I removed the 'if
(musb_dma_inventra())' block that had the FLUSHFIFIO, but when I tested
it it still worked. In fact, I reverted this last diff chunk and it
still worked.


Paul

Re: [PATCH v2] usb: gadget: musb: fix short isoc packets with inventra dma

[Bin Liu]

Hi Paul,

On Fri, Jan 11, 2019 at 12:31:59AM -0500, Paul Elder wrote:
> Hi Bin,
> 
> On Wed, Jan 09, 2019 at 09:02:15AM -0600, Bin Liu wrote:
> > Hi Paul,
> > 
> > On Wed, Jan 09, 2019 at 02:10:09AM -0500, Paul Elder wrote:
> > > Handling short packets (length < max packet size) in the Inventra DMA
> > > engine in the MUSB driver causes the MUSB DMA controller to hang. An
> > > example of a problem that is caused by this problem is when streaming
> > > video out of a UVC gadget, only the first video frame is transferred.
> > > 
> > > For short packets (mode-0 or mode-1 DMA), MUSB_TXCSR_TXPKTRDY must be
> > > set manually by the driver. This was previously done in musb_g_tx
> > > (musb_gadget.c), but incorrectly (all csr flags were cleared, and only
> > > MUSB_TXCSR_MODE and MUSB_TXCSR_TXPKTRDY were set). Fixing that problem
> > > allows some requests to be transferred correctly, but multiple requests
> > > were often put together in one USB packet, and caused problems if the
> > > packet size was not a multiple of 4. Instead, set MUSB_TXCSR_TXPKTRDY
> > > in dma_controller_irq (musbhsdma.c), just like host mode transfers.
> > > 
> > > This topic was originally tackled by Nicolas Boichat [0] [1] and is
> > > discussed further at [2] as part of his GSoC project [3].
> > > 
> > > [0] https://groups.google.com/forum/?hl=en#!topic/beagleboard-gsoc/k8Azwfp75CU
> > > [1] https://gitorious.org/beagleboard-usbsniffer/beagleboard-usbsniffer-kernel/commit/b0be3b6cc195ba732189b04f1d43ec843c3e54c9?p=beagleboard-usbsniffer:beagleboard-usbsniffer-kernel.git;a=patch;h=b0be3b6cc195ba732189b04f1d43ec843c3e54c9
> > > [2] http://beagleboard-usbsniffer.blogspot.com/2010/07/musb-isochronous-transfers-fixed.html
> > > [3] http://elinux.org/BeagleBoard/GSoC/USBSniffer
> > > 
> > > Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
> > > ---
> > > Changes in v2:
> > > 
> > > - no more flushing FIFO
> > > - greatly simplified short packet if guard in musb_g_tx, and removed
> > >   unnecessary variables
> > > - minor indentation and wording changes
> > > 
> > >  drivers/usb/musb/musb_gadget.c | 19 +++++--------------
> > >  drivers/usb/musb/musbhsdma.c   | 21 +++++++++++----------
> > >  2 files changed, 16 insertions(+), 24 deletions(-)
> > > 
> > > diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
> > > index eae8b1b1b45b..496643f54faa 100644
> > > --- a/drivers/usb/musb/musb_gadget.c
> > > +++ b/drivers/usb/musb/musb_gadget.c
> > > @@ -452,13 +452,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
> > >  	}
> > >  
> > >  	if (request) {
> > > -		u8	is_dma = 0;
> > > -		bool	short_packet = false;
> > >  
> > >  		trace_musb_req_tx(req);
> > >  
> > >  		if (dma && (csr & MUSB_TXCSR_DMAENAB)) {
> > > -			is_dma = 1;
> > >  			csr |= MUSB_TXCSR_P_WZC_BITS;
> > >  			csr &= ~(MUSB_TXCSR_DMAENAB | MUSB_TXCSR_P_UNDERRUN |
> > >  				 MUSB_TXCSR_TXPKTRDY | MUSB_TXCSR_AUTOSET);
> > > @@ -476,16 +473,8 @@ void musb_g_tx(struct musb *musb, u8 epnum)
> > >  		 */
> > >  		if ((request->zero && request->length)
> > >  			&& (request->length % musb_ep->packet_sz == 0)
> > > -			&& (request->actual == request->length))
> > > -				short_packet = true;
> > > +			&& (request->actual == request->length)) {
> > >  
> > > -		if ((musb_dma_inventra(musb) || musb_dma_ux500(musb)) &&
> > > -			(is_dma && (!dma->desired_mode ||
> > > -				(request->actual &
> > > -					(musb_ep->packet_sz - 1)))))
> > > -				short_packet = true;
> > > -
> > > -		if (short_packet) {
> > >  			/*
> > >  			 * On DMA completion, FIFO may not be
> > >  			 * available yet...
> > > @@ -493,8 +482,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
> > >  			if (csr & MUSB_TXCSR_TXPKTRDY)
> > >  				return;
> > >  
> > > -			musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE
> > > -					| MUSB_TXCSR_TXPKTRDY);
> > > +			musb_dbg(musb, "sending short pkt (zero=%d, length=%d, actual=%d, dma->desired_mode=%d)\n",
> > > +				 request->zero, request->length, request->actual,
> > > +				 dma->desired_mode);
> > > +			musb_writew(epio, MUSB_TXCSR, csr | MUSB_TXCSR_TXPKTRDY);
> > 
> > Sorry I didn't catch this in the last review, but this change seems not
> > required, isn't it? In the first version of the patch, the code is
> > 'returned' in the 'if (musb_dma_inventra())' branch above, doesn't reach
> > here.
> 
> Do you mean change compared to the last version of the patch, or this
> last chunk of the diff?

I meant that the chunk above seems not related to this webcam short
packet test case, so am wondering if this change is not neccessary

-                  musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE
-                                 | MUSB_TXCSR_TXPKTRDY);
+                 musb_writew(epio, MUSB_TXCSR, csr | MUSB_TXCSR_TXPKTRDY);


> 
> I guess I did also remove the return when I removed the 'if
> (musb_dma_inventra())' block that had the FLUSHFIFIO, but when I tested
> it it still worked. In fact, I reverted this last diff chunk and it
> still worked.

so the last chunk is not related, we don't have to touch it.

Regards,
-Bin.