[PATCH] musb: Add workqueue for URB giveback

[PATCH] musb: Add workqueue for URB giveback

[Ajay Kumar Gupta]

Current musb host driver does the giveback of completed urb first and
then start the next request. This is significantly affecting the streaming
from an USB camera wherein we observe huge delay between the two IN tokens
from musb host. This is due to the fact that UVC driver is doing decoding
and further processing in giveback context.

The patch tries to defer the giveback part to a workqueue and continues
with the start of new request in completion path.

Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>
---
Patch created against latest linus's tree and all musb patches in
Greg's queue.
Patch is also updated with the comments from Alan on handling
URBs which got completed with errors.

 drivers/usb/musb/musb_core.c |   22 +++++++++
 drivers/usb/musb/musb_core.h |   18 +++++++
 drivers/usb/musb/musb_host.c |  107 ++++++++++++++++++++++++++++++++++++++----
 drivers/usb/musb/musb_host.h |    2 +
 4 files changed, 139 insertions(+), 10 deletions(-)

diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
index 0f13ded..9ce21ec 100644
--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -1857,6 +1857,9 @@ static void musb_free(struct musb *musb)
 	}
 
 #ifdef CONFIG_USB_MUSB_HDRC_HCD
+	if (musb->gb_queue)
+		destroy_workqueue(musb->gb_queue);
+	free_queue(musb);
 	usb_put_hcd(musb_to_hcd(musb));
 #else
 	kfree(musb);
@@ -1915,6 +1918,9 @@ bad_config:
 		return -ENOMEM;
 
 	spin_lock_init(&musb->lock);
+#ifdef CONFIG_USB_MUSB_HDRC_HCD
+	spin_lock_init(&musb->qlock);
+#endif
 	musb->board_mode = plat->mode;
 	musb->board_set_power = plat->set_power;
 	musb->set_clock = plat->set_clock;
@@ -2078,8 +2084,24 @@ bad_config:
 			? "DMA" : "PIO",
 			musb->nIrq);
 
+#ifdef CONFIG_USB_MUSB_HDRC_HCD
+	musb->gb_queue = create_singlethread_workqueue(dev_name(dev));
+	if (musb->gb_queue == NULL)
+		goto fail2;
+	/* Init giveback workqueue */
+	INIT_WORK(&musb->gb_work, musb_gb_work);
+
+	/* init queue */
+	init_queue(musb);
+	if (!musb->qhead)
+		goto fail3;
+#endif
 	return 0;
 
+#ifdef CONFIG_USB_MUSB_HDRC_HCD
+fail3:
+	destroy_workqueue(musb->gb_queue);
+#endif
 fail2:
 	musb_platform_exit(musb);
 fail:
diff --git a/drivers/usb/musb/musb_core.h b/drivers/usb/musb/musb_core.h
index 17e7115..ef93c13 100644
--- a/drivers/usb/musb/musb_core.h
+++ b/drivers/usb/musb/musb_core.h
@@ -322,6 +322,16 @@ static inline struct usb_request *next_out_request(struct musb_hw_ep *hw_ep)
 #endif
 }
 
+#ifdef CONFIG_USB_MUSB_HDRC_HCD
+/*
+ * struct queue - Queue data structure
+ */
+struct queue {
+	struct urb *urb;
+	struct queue *next;
+};
+#endif
+
 /*
  * struct musb - Driver instance data.
  */
@@ -355,6 +365,11 @@ struct musb {
 	struct list_head	in_bulk;	/* of musb_qh */
 	struct list_head	out_bulk;	/* of musb_qh */
 
+	struct workqueue_struct *gb_queue;
+	struct work_struct      gb_work;
+	spinlock_t		qlock;
+	struct queue		*qhead;
+
 	struct timer_list	otg_timer;
 #endif
 
@@ -610,5 +625,8 @@ extern int musb_platform_get_vbus_status(struct musb *musb);
 
 extern int __init musb_platform_init(struct musb *musb);
 extern int musb_platform_exit(struct musb *musb);
+#ifdef CONFIG_USB_MUSB_HDRC_HCD
+extern void musb_gb_work(struct work_struct *data);
+#endif
 
 #endif	/* __MUSB_CORE_H__ */
diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index 3421cf9..33a4568 100644
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -99,7 +99,56 @@
 static void musb_ep_program(struct musb *musb, u8 epnum,
 			struct urb *urb, int is_out,
 			u8 *buf, u32 offset, u32 len);
+struct queue *create(void)
+{
+	struct queue *new;
+	new = kmalloc(sizeof(struct queue), GFP_ATOMIC);
+	if (!new)
+		return NULL;
+	new->next = NULL;
+	return new;
+}
+void push_queue(struct musb *musb, struct urb *urb)
+{
+	struct queue *new, *temp;
+
+	new = create();
+	new->urb = urb;
+
+	temp = musb->qhead;
+
+	spin_lock(&musb->qlock);
+	while (temp->next != NULL)
+		temp = temp->next;
+	temp->next = new;
+	spin_unlock(&musb->qlock);
+}
+
+struct urb *pop_queue(struct musb *musb)
+{
+	struct urb *urb;
+	struct queue *head = musb->qhead;
+	struct queue *temp;
+	unsigned long flags;
+
+	spin_lock_irqsave(&musb->qlock, flags);
+	temp = head->next;
+	if (!temp) {
+		spin_unlock_irqrestore(&musb->qlock, flags);
+		return NULL;
+	}
+	head->next = head->next->next;
+	spin_unlock_irqrestore(&musb->qlock, flags);
+
+	urb = temp->urb;
+	kfree(temp);
+	return urb;
+}
 
+void init_queue(struct musb *musb)
+{
+	musb->qhead = create();
+}
 /*
  * Clear TX fifo. Needed to avoid BABBLE errors.
  */
@@ -297,8 +346,6 @@ start:
 
 /* Context: caller owns controller lock, IRQs are blocked */
 static void musb_giveback(struct musb *musb, struct urb *urb, int status)
-__releases(musb->lock)
-__acquires(musb->lock)
 {
 	DBG(({ int level; switch (status) {
 				case 0:
@@ -323,10 +370,20 @@ __acquires(musb->lock)
 			urb->actual_length, urb->transfer_buffer_length
 			);
 
-	usb_hcd_unlink_urb_from_ep(musb_to_hcd(musb), urb);
-	spin_unlock(&musb->lock);
 	usb_hcd_giveback_urb(musb_to_hcd(musb), urb, status);
-	spin_lock(&musb->lock);
+}
+
+void free_queue(struct musb *musb)
+{
+	struct urb *urb;
+
+	/* giveback any urb still in queue */
+	while ((urb = pop_queue(musb)) != 0)
+		musb_giveback(musb, urb, 0);
+
+	/* free up the queue head memory */
+	kfree(musb->qhead);
+	musb->qhead = NULL;
 }
 
 /* For bulk/interrupt endpoints only */
@@ -348,6 +405,15 @@ static inline void musb_save_toggle(struct musb_qh *qh, int is_in,
 
 	usb_settoggle(urb->dev, qh->epnum, !is_in, csr ? 1 : 0);
 }
+/* Used to complete urb giveback */
+void musb_gb_work(struct work_struct *data)
+{
+	struct musb *musb = container_of(data, struct musb, gb_work);
+	struct urb *urb;
+
+	while ((urb = pop_queue(musb)) != 0)
+		musb_giveback(musb, urb, 0);
+}
 
 /*
  * Advance this hardware endpoint's queue, completing the specified URB and
@@ -378,10 +444,16 @@ static void musb_advance_schedule(struct musb *musb, struct urb *urb,
 		break;
 	}
 
-	qh->is_ready = 0;
-	musb_giveback(musb, urb, status);
-	qh->is_ready = ready;
+	usb_hcd_unlink_urb_from_ep(musb_to_hcd(musb), urb);
 
+	/* If URB completed with error then giveback first */
+	if (status != 0) {
+		qh->is_ready = 0;
+		spin_unlock(&musb->lock);
+		musb_giveback(musb, urb, status);
+		spin_lock(&musb->lock);
+		qh->is_ready = ready;
+	}
 	/* reclaim resources (and bandwidth) ASAP; deschedule it, and
 	 * invalidate qh as soon as list_empty(&hep->urb_list)
 	 */
@@ -429,6 +501,12 @@ static void musb_advance_schedule(struct musb *musb, struct urb *urb,
 		    hw_ep->epnum, is_in ? 'R' : 'T', next_urb(qh));
 		musb_start_urb(musb, is_in, qh);
 	}
+
+	/* if URB is successfully completed then giveback in workqueue */
+	if (status == 0) {
+		push_queue(musb, urb);
+		queue_work(musb->gb_queue, &musb->gb_work);
+	}
 }
 
 static u16 musb_h_flush_rxfifo(struct musb_hw_ep *hw_ep, u16 csr)
@@ -2167,8 +2245,12 @@ static int musb_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
 			|| musb_ep_get_qh(qh->hw_ep, is_in) != qh) {
 		int	ready = qh->is_ready;
 
+		usb_hcd_unlink_urb_from_ep(musb_to_hcd(musb), urb);
+
 		qh->is_ready = 0;
+		spin_unlock(&musb->lock);
 		musb_giveback(musb, urb, 0);
+		spin_lock(&musb->lock);
 		qh->is_ready = ready;
 
 		/* If nothing else (usually musb_giveback) is using it
@@ -2229,8 +2311,13 @@ musb_h_disable(struct usb_hcd *hcd, struct usb_host_endpoint *hep)
 		 * other transfers, and since !qh->is_ready nothing
 		 * will activate any of these as it advances.
 		 */
-		while (!list_empty(&hep->urb_list))
-			musb_giveback(musb, next_urb(qh), -ESHUTDOWN);
+		while (!list_empty(&hep->urb_list)) {
+			urb = next_urb(qh);
+			usb_hcd_unlink_urb_from_ep(musb_to_hcd(musb), urb);
+			spin_unlock(&musb->lock);
+			musb_giveback(musb, urb, -ESHUTDOWN);
+			spin_lock(&musb->lock);
+		}
 
 		hep->hcpriv = NULL;
 		list_del(&qh->ring);
diff --git a/drivers/usb/musb/musb_host.h b/drivers/usb/musb/musb_host.h
index 14b0077..a1a01df 100644
--- a/drivers/usb/musb/musb_host.h
+++ b/drivers/usb/musb/musb_host.h
@@ -83,6 +83,8 @@ static inline struct musb_qh *first_qh(struct list_head *q)
 
 
 extern void musb_root_disconnect(struct musb *musb);
+extern void init_queue(struct musb *musb);
+extern void free_queue(struct musb *musb);
 
 struct usb_hcd;
 
-- 
1.6.2.4

Re: [PATCH] musb: Add workqueue for URB giveback

[Oliver Neukum]

Am Freitag, 26. Februar 2010 11:39:06 schrieb Ajay Kumar Gupta:
> +struct queue *create(void)
> +{
> +       struct queue *new;
> +       new = kmalloc(sizeof(struct queue), GFP_ATOMIC);
> +       if (!new)
> +               return NULL;
> +       new->next = NULL;
> +       return new;
> +}
> +void push_queue(struct musb *musb, struct urb *urb)
> +{
> +       struct queue *new, *temp;
> +
> +       new = create();
> +       new->urb = urb;

And you happily follow the NULL pointer in the error case.

> +
> +       temp = musb->qhead;
> +
> +       spin_lock(&musb->qlock);
> +       while (temp->next != NULL)
> +               temp = temp->next;
> +       temp->next = new;
> +       spin_unlock(&musb->qlock);
> +}

A design allocating memory in giveback is problematic. At least you need
to handle a failure to allocate memory. But you'd better handle this by putting
the list into the private part of the URB.

	Regards
		Oliver

RE: [PATCH] musb: Add workqueue for URB giveback

[Gupta, Ajay Kumar]

Hi,
> -----Original Message-----
> From: Oliver Neukum [mailto:oliver-GvhC2dPhHPQdnm+yROfE0A@public.gmane.org]
> Sent: Friday, February 26, 2010 4:33 PM
> To: Gupta, Ajay Kumar
> Cc: linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org;
> stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org
> Subject: Re: [PATCH] musb: Add workqueue for URB giveback
> 
> Am Freitag, 26. Februar 2010 11:39:06 schrieb Ajay Kumar Gupta:
> > +struct queue *create(void)
> > +{
> > +       struct queue *new;
> > +       new = kmalloc(sizeof(struct queue), GFP_ATOMIC);
> > +       if (!new)
> > +               return NULL;
> > +       new->next = NULL;
> > +       return new;
> > +}
> > +void push_queue(struct musb *musb, struct urb *urb)
> > +{
> > +       struct queue *new, *temp;
> > +
> > +       new = create();
> > +       new->urb = urb;
> 
> And you happily follow the NULL pointer in the error case.

I will put the NULL check here and also during push_queue(). In case
Of memory allocation failure I can giveback the URB right away.

> 
> > +
> > +       temp = musb->qhead;
> > +
> > +       spin_lock(&musb->qlock);
> > +       while (temp->next != NULL)
> > +               temp = temp->next;
> > +       temp->next = new;
> > +       spin_unlock(&musb->qlock);
> > +}
> 
> A design allocating memory in giveback is problematic. At least you need
> to handle a failure to allocate memory. But you'd better handle this by
> putting the list into the private part of the URB.

This would require a change in urb structure which would face more
resistance as it will only be used by MUSB HCD.

Thanks,
Ajay
> 
> 	Regards
> 		Oliver
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Re: [PATCH] musb: Add workqueue for URB giveback

[Oliver Neukum]

Am Freitag, 26. Februar 2010 12:20:05 schrieb Gupta, Ajay Kumar:

Hello,

> > -----Original Message-----
> > From: Oliver Neukum [mailto:oliver-GvhC2dPhHPQdnm+yROfE0A@public.gmane.org]
> > Sent: Friday, February 26, 2010 4:33 PM
> > To: Gupta, Ajay Kumar
> > Cc: linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org;
> > stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org
> > Subject: Re: [PATCH] musb: Add workqueue for URB giveback
> > 
> > Am Freitag, 26. Februar 2010 11:39:06 schrieb Ajay Kumar Gupta:
> > > +struct queue *create(void)
> > > +{
> > > +       struct queue *new;
> > > +       new = kmalloc(sizeof(struct queue), GFP_ATOMIC);
> > > +       if (!new)
> > > +               return NULL;
> > > +       new->next = NULL;
> > > +       return new;
> > > +}
> > > +void push_queue(struct musb *musb, struct urb *urb)
> > > +{
> > > +       struct queue *new, *temp;
> > > +
> > > +       new = create();
> > > +       new->urb = urb;
> > 
> > And you happily follow the NULL pointer in the error case.
> 
> I will put the NULL check here and also during push_queue(). In case
> Of memory allocation failure I can giveback the URB right away.

If you do that you'll give back URBs out of order. Now I don't know whether
this is defined as something you mustn't do, bad it is not a good idea.

	Regards
		Oliver
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RE: [PATCH] musb: Add workqueue for URB giveback

[Gupta, Ajay Kumar]

Hi,
> > > Am Freitag, 26. Februar 2010 11:39:06 schrieb Ajay Kumar Gupta:
> > > > +struct queue *create(void)
> > > > +{
> > > > +       struct queue *new;
> > > > +       new = kmalloc(sizeof(struct queue), GFP_ATOMIC);
> > > > +       if (!new)
> > > > +               return NULL;
> > > > +       new->next = NULL;
> > > > +       return new;
> > > > +}
> > > > +void push_queue(struct musb *musb, struct urb *urb)
> > > > +{
> > > > +       struct queue *new, *temp;
> > > > +
> > > > +       new = create();
> > > > +       new->urb = urb;
> > >
> > > And you happily follow the NULL pointer in the error case.
> >
> > I will put the NULL check here and also during push_queue(). In case
> > Of memory allocation failure I can giveback the URB right away.
> 
> If you do that you'll give back URBs out of order.

Right, this would confuse the class driver and better avoided.

Next option is to add another list_head within URB structure to trace
the URBs. (as you suggested earlier)

-Ajay  

> Now I don't know whether this is defined as something you mustn't
> do, bad it is not a good idea.
> 
> 	Regards
> 		Oliver

Re: [PATCH] musb: Add workqueue for URB giveback

[Laurent Pinchart]

Hi Ajay,

On Friday 26 February 2010 11:39:06 Ajay Kumar Gupta wrote:
> Current musb host driver does the giveback of completed urb first and
> then start the next request. This is significantly affecting the streaming
> from an USB camera wherein we observe huge delay between the two IN tokens
> from musb host. This is due to the fact that UVC driver is doing decoding
> and further processing in giveback context.

I was thinking about adding a workqueue to the UVC driver for URB processing. 
If you beat my by writing a patch before I find time to do so, I won't 
complain ;-)

-- 
Regards,

Laurent Pinchart

RE: [PATCH] musb: Add workqueue for URB giveback

[Gupta, Ajay Kumar]

Hi,
> -----Original Message-----
> From: Laurent Pinchart [mailto:laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org]
> Sent: Friday, February 26, 2010 5:04 PM
> To: Gupta, Ajay Kumar
> Cc: linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org;
> stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org; oliver-GvhC2dPhHPQdnm+yROfE0A@public.gmane.org
> Subject: Re: [PATCH] musb: Add workqueue for URB giveback
> 
> Hi Ajay,
> 
> On Friday 26 February 2010 11:39:06 Ajay Kumar Gupta wrote:
> > Current musb host driver does the giveback of completed urb first and
> > then start the next request. This is significantly affecting the
> streaming
> > from an USB camera wherein we observe huge delay between the two IN
> tokens
> > from musb host. This is due to the fact that UVC driver is doing
> decoding
> > and further processing in giveback context.
> 
> I was thinking about adding a workqueue to the UVC driver for URB
> processing.
> If you beat my by writing a patch before I find time to do so, I won't
> complain ;-)

Sure, I will see when I can post a RFC/PATCH for it. Probably after
two weeks.

Regards,
Ajay
> 
> --
> Regards,
> 
> Laurent Pinchart
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Re: [PATCH] musb: Add workqueue for URB giveback

[David Vrabel]

Ajay Kumar Gupta wrote:
> Current musb host driver does the giveback of completed urb first and
> then start the next request. This is significantly affecting the streaming
> from an USB camera wherein we observe huge delay between the two IN tokens
> from musb host. This is due to the fact that UVC driver is doing decoding
> and further processing in giveback context.
> 
> The patch tries to defer the giveback part to a workqueue and continues
> with the start of new request in completion path.

Suggest allocating a per-urb structure when a new URB is enqueued.  This
structure contains the completion/giveback work item.  This avoids
having to a) allocate memory on completion; b) create a second queue
structure.

David
-- 
David Vrabel, Senior Software Engineer, Drivers
CSR, Churchill House, Cambridge Business Park,  Tel: +44 (0)1223 692562
Cowley Road, Cambridge, CB4 0WZ                 http://www.csr.com/


Member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom