[PATCHv2 1/2] musb: NAK timeout scheme on bulk reserved ep

[Ajay Kumar Gupta <ajay.gupta@ti.com>]

Fixes endpoint starvation issue when more than one bulk qhs
are multiplexed on reserved bulk endpoint.NAK timeout interval
is set for such qhs and next qh is scheduled when NAK timeout
occurs.
This scheme doesn't work for devices which are connected to a
high to full speed tree as there is no NAK timeout interrupt
at musb controller from such devices.

Signed-off-by: Ravi Babu <ravibabu@ti.com>
Signed-off-by: Swaminathan S <swami.iyer@ti.com>
Signed-off-by: Thomas Abraham <t-abraham@ti.com>
Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>
---
These patches have been created against latest omap git and Felipe's
musb .28 patch series at,
http://marc.info/?l=linux-usb&m=122528597116718&w=2

 drivers/usb/musb/musb_host.c |   64 ++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index 30b5685..0b40a00 100644
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -1378,6 +1378,50 @@ finish:
 
 #endif
 
+/* Schedule next qh from musb->in_bulk and add the current qh at tail
+ * to avoid endpoint starvation.
+ */
+static void musb_bulk_nak_timeout(struct musb *musb, struct musb_hw_ep *ep)
+{
+	struct dma_channel	*dma;
+	struct urb	*urb;
+	void __iomem	*mbase = musb->mregs;
+	void __iomem	*epio = ep->regs;
+	struct musb_qh	*cur_qh, *next_qh;
+	u16	rx_csr;
+
+	musb_ep_select(mbase, ep->epnum);
+	dma = is_dma_capable() ? ep->rx_channel : NULL;
+
+	/* clear nak timeout bit */
+	rx_csr = musb_readw(epio, MUSB_RXCSR);
+	rx_csr &= ~MUSB_RXCSR_DATAERROR;
+	musb_writew(epio, MUSB_RXCSR, rx_csr);
+
+	cur_qh = first_qh(&musb->in_bulk);
+	if (cur_qh) {
+		urb = next_urb(cur_qh);
+		if (dma_channel_status(dma) == MUSB_DMA_STATUS_BUSY) {
+			dma->status = MUSB_DMA_STATUS_CORE_ABORT;
+			musb->dma_controller->channel_abort(dma);
+			urb->actual_length += dma->actual_len;
+			dma->actual_len = 0L;
+		}
+		musb_save_toggle(ep, 1, urb);
+
+		/* delete cur_qh and add to tail to musb->in_bulk */
+		list_del(&cur_qh->ring);
+		list_add_tail(&cur_qh->ring, &musb->in_bulk);
+
+		/* get the next qh from musb->in_bulk */
+		next_qh = first_qh(&musb->in_bulk);
+
+		/* set rx_reinit and schedule the next qh */
+		ep->rx_reinit = 1;
+		musb_start_urb(musb, 1, next_qh);
+	}
+}
+
 /*
  * Service an RX interrupt for the given IN endpoint; docs cover bulk, iso,
  * and high-bandwidth IN transfer cases.
@@ -1449,10 +1493,14 @@ void musb_host_rx(struct musb *musb, u8 epnum)
 			 * we have a candidate... NAKing is *NOT* an error
 			 */
 			DBG(6, "RX end %d NAK timeout\n", epnum);
+			if (usb_pipebulk(urb->pipe) && qh->mux == 1 &&
+				!list_is_singular(&musb->in_bulk)) {
+				musb_bulk_nak_timeout(musb, hw_ep);
+				return;
+			}
 			musb_ep_select(mbase, epnum);
-			musb_writew(epio, MUSB_RXCSR,
-					MUSB_RXCSR_H_WZC_BITS
-					| MUSB_RXCSR_H_REQPKT);
+			rx_csr &= ~MUSB_RXCSR_DATAERROR;
+			musb_writew(epio, MUSB_RXCSR, rx_csr);
 
 			goto finish;
 		} else {
@@ -1795,6 +1843,16 @@ static int musb_schedule(
 			head = &musb->in_bulk;
 		else
 			head = &musb->out_bulk;
+		/* Enable bulk NAK time out scheme when bulk requests are
+		 * multiplxed.This scheme doen't work in high speed to full
+		 * speed scenario as NAK interrupts are not coming from a
+		 * full speed device connected to a high speed device.
+		 * NAK timeout interval is 8 (128 uframe or 16ms) for HS and
+		 * 4 (8 frame or 8ms) for FS device.
+		 */
+		if (is_in && qh->dev)
+			qh->intv_reg =
+				(USB_SPEED_HIGH == qh->dev->speed) ? 8 : 4;
 		goto success;
 	} else if (best_end < 0) {
 		return -ENOSPC;
-- 
1.5.6