linux-kernel - [PATCH 5.4 061/177] usb: dwc3: gadget: Properly track pending and queued SG

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Message-Id: <20210531130650.013959872@linuxfoundation.org>
Date:   Mon, 31 May 2021 15:13:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Michael Grzeschik <m.grzeschik@...gutronix.de>,
        Felipe Balbi <balbi@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Subject: [PATCH 5.4 061/177] usb: dwc3: gadget: Properly track pending and queued SG

From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>

commit 25dda9fc56bd90d45f9a4516bcfa5211e61b4290 upstream.

The driver incorrectly uses req->num_pending_sgs to track both the
number of pending and queued SG entries. It only prepares the next
request if the previous is done, and it doesn't update num_pending_sgs
until there is TRB completion interrupt. This may starve the controller
of more TRBs until the num_pending_sgs is decremented.

Fix this by decrementing the num_pending_sgs after they are queued and
properly track both num_mapped_sgs and num_queued_sgs.

Fixes: c96e6725db9d ("usb: dwc3: gadget: Correct the logic for queuing sgs")
Cc: <stable@...r.kernel.org>
Reported-by: Michael Grzeschik <m.grzeschik@...gutronix.de>
Tested-by: Michael Grzeschik <m.grzeschik@...gutronix.de>
Acked-by: Felipe Balbi <balbi@...nel.org>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Link: https://lore.kernel.org/r/ba24591dbcaad8f244a3e88bd449bb7205a5aec3.1620874069.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/usb/dwc3/gadget.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1162,6 +1162,7 @@ static void dwc3_prepare_one_trb_sg(stru
 			req->start_sg = sg_next(s);
 
 		req->num_queued_sgs++;
+		req->num_pending_sgs--;
 
 		/*
 		 * The number of pending SG entries may not correspond to the
@@ -1169,7 +1170,7 @@ static void dwc3_prepare_one_trb_sg(stru
 		 * don't include unused SG entries.
 		 */
 		if (length == 0) {
-			req->num_pending_sgs -= req->request.num_mapped_sgs - req->num_queued_sgs;
+			req->num_pending_sgs = 0;
 			break;
 		}
 
@@ -2602,15 +2603,15 @@ static int dwc3_gadget_ep_reclaim_trb_sg
 	struct dwc3_trb *trb = &dep->trb_pool[dep->trb_dequeue];
 	struct scatterlist *sg = req->sg;
 	struct scatterlist *s;
-	unsigned int pending = req->num_pending_sgs;
+	unsigned int num_queued = req->num_queued_sgs;
 	unsigned int i;
 	int ret = 0;
 
-	for_each_sg(sg, s, pending, i) {
+	for_each_sg(sg, s, num_queued, i) {
 		trb = &dep->trb_pool[dep->trb_dequeue];
 
 		req->sg = sg_next(s);
-		req->num_pending_sgs--;
+		req->num_queued_sgs--;
 
 		ret = dwc3_gadget_ep_reclaim_completed_trb(dep, req,
 				trb, event, status, true);
@@ -2633,7 +2634,7 @@ static int dwc3_gadget_ep_reclaim_trb_li
 
 static bool dwc3_gadget_ep_request_completed(struct dwc3_request *req)
 {
-	return req->num_pending_sgs == 0;
+	return req->num_pending_sgs == 0 && req->num_queued_sgs == 0;
 }
 
 static int dwc3_gadget_ep_cleanup_completed_request(struct dwc3_ep *dep,
@@ -2642,7 +2643,7 @@ static int dwc3_gadget_ep_cleanup_comple
 {
 	int ret;
 
-	if (req->num_pending_sgs)
+	if (req->request.num_mapped_sgs)
 		ret = dwc3_gadget_ep_reclaim_trb_sg(dep, req, event,
 				status);
 	else