[PATCH v2] usb: xhci: Add support for URB_ZERO_PACKET to bulk/sg transfers

[Reyad Attiyat]

This commmit checks for the URB_ZERO_PACKET flag and creates an extra
zero-length td if the urb transfer length is a multiple of the endpoint's
max packet length.

Signed-off-by: Reyad Attiyat <reyad.attiyat@xxxxxxxxx>
---
 drivers/usb/host/xhci-ring.c | 43 +++++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 10 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 7d34cbf..3d57a7a 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3040,7 +3040,9 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 	int num_sgs;
 	int trb_buff_len, this_sg_len, running_total;
 	unsigned int total_packet_count;
+	bool zero_length_needed;
 	bool first_trb;
+	int last_trb;
 	u64 addr;
 	bool more_trbs_coming;
 
@@ -3056,6 +3058,14 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 	total_packet_count = DIV_ROUND_UP(urb->transfer_buffer_length,
 			usb_endpoint_maxp(&urb->ep->desc));
 
+	/* Deal with URB_ZERO_PACKET - need one more td/trb */
+	zero_length_needed = (urb->transfer_flags & URB_ZERO_PACKET)
+	 && !(urb->transfer_buffer_length % usb_endpoint_maxp(&urb->ep->desc));
+	if(zero_length_needed){
+		num_trbs++;
+		xhci_dbg(xhci, "Creating zero length td.\n");
+	}
+
 	trb_buff_len = prepare_transfer(xhci, xhci->devs[slot_id],
 			ep_index, urb->stream_id,
 			num_trbs, urb, 0, mem_flags);
@@ -3092,6 +3102,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		trb_buff_len = urb->transfer_buffer_length;
 
 	first_trb = true;
+	last_trb = zero_length_needed ? 2 : 1;
 	/* Queue the first TRB, even if it's zero-length */
 	do {
 		u32 field = 0;
@@ -3109,12 +3120,13 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		/* Chain all the TRBs together; clear the chain bit in the last
 		 * TRB to indicate it's the last TRB in the chain.
 		 */
-		if (num_trbs > 1) {
+		if (num_trbs > last_trb) {
 			field |= TRB_CHAIN;
-		} else {
-			/* FIXME - add check for ZERO_PACKET flag before this */
+		} else if (num_trbs == last_trb) {
 			td->last_trb = ep_ring->enqueue;
 			field |= TRB_IOC;
+		} else if (zero_length_needed && num_trbs == 1) {
+			trb_buff_len = 0;
 		}
 
 		/* Only set interrupt on short packet for IN endpoints */
@@ -3176,7 +3188,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		if (running_total + trb_buff_len > urb->transfer_buffer_length)
 			trb_buff_len =
 				urb->transfer_buffer_length - running_total;
-	} while (running_total < urb->transfer_buffer_length);
+	} while (num_trbs > 0);
 
 	check_trb_math(urb, num_trbs, running_total);
 	giveback_first_trb(xhci, slot_id, ep_index, urb->stream_id,
@@ -3194,7 +3206,9 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 	int num_trbs;
 	struct xhci_generic_trb *start_trb;
 	bool first_trb;
+	int last_trb;
 	bool more_trbs_coming;
+	bool zero_length_needed;
 	int start_cycle;
 	u32 field, length_field;
 
@@ -3225,7 +3239,14 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		num_trbs++;
 		running_total += TRB_MAX_BUFF_SIZE;
 	}
-	/* FIXME: this doesn't deal with URB_ZERO_PACKET - need one more */
+
+	/* Deal with URB_ZERO_PACKET - need one more td/trb */
+	zero_length_needed = (urb->transfer_flags & URB_ZERO_PACKET)
+	 && !(urb->transfer_buffer_length % usb_endpoint_maxp(&urb->ep->desc));
+	if(zero_length_needed){
+		num_trbs++;
+		xhci_dbg(xhci, "Creating zero length td.\n");
+	}
 
 	ret = prepare_transfer(xhci, xhci->devs[slot_id],
 			ep_index, urb->stream_id,
@@ -3255,7 +3276,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		trb_buff_len = urb->transfer_buffer_length;
 
 	first_trb = true;
-
+	last_trb = zero_length_needed ? 2 : 1;
 	/* Queue the first TRB, even if it's zero-length */
 	do {
 		u32 remainder = 0;
@@ -3272,12 +3293,14 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		/* Chain all the TRBs together; clear the chain bit in the last
 		 * TRB to indicate it's the last TRB in the chain.
 		 */
-		if (num_trbs > 1) {
+
+		if (num_trbs > last_trb) {
 			field |= TRB_CHAIN;
-		} else {
-			/* FIXME - add check for ZERO_PACKET flag before this */
+		} else if (num_trbs == last_trb) {
 			td->last_trb = ep_ring->enqueue;
 			field |= TRB_IOC;
+		} else if (zero_length_needed && num_trbs == 1) {
+			trb_buff_len = 0;
 		}
 
 		/* Only set interrupt on short packet for IN endpoints */
@@ -3315,7 +3338,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		trb_buff_len = urb->transfer_buffer_length - running_total;
 		if (trb_buff_len > TRB_MAX_BUFF_SIZE)
 			trb_buff_len = TRB_MAX_BUFF_SIZE;
-	} while (running_total < urb->transfer_buffer_length);
+	} while (num_trbs > 0);
 
 	check_trb_math(urb, num_trbs, running_total);
 	giveback_first_trb(xhci, slot_id, ep_index, urb->stream_id,
-- 
2.4.3

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