Patchwork [3.5.y.z,extended,stable] Patch "b43: A fix for DMA transmission sequence errors" has been added to staging queue

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Submitter Luis Henriques
Date April 4, 2013, 1:25 p.m.
Message ID <1365081957-15173-1-git-send-email-luis.henriques@canonical.com>
Download mbox | patch
Permalink /patch/233811/
State New
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Comments

Luis Henriques - April 4, 2013, 1:25 p.m.
This is a note to let you know that I have just added a patch titled

    b43: A fix for DMA transmission sequence errors

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

From 7a00c108e5589e7b1b54c349ffef54306ce59a0b Mon Sep 17 00:00:00 2001
From: "Iestyn C. Elfick" <isedev@gmail.com>
Date: Wed, 20 Mar 2013 14:02:31 -0500
Subject: [PATCH] b43: A fix for DMA transmission sequence errors

commit b251412db99ccd4495ce372fec7daee27bf06923 upstream.

Intermittently, b43 will report "Out of order TX status report on DMA ring".
When this happens, the driver must be reset before communication can resume.
The cause of the problem is believed to be an error in the closed-source
firmware; however, all versions of the firmware are affected.

This change uses the observation that the expected status is always 2 less
than the observed value, and supplies a fake status report to skip one
header/data pair.

Not all devices suffer from this problem, but it can occur several times
per second under heavy load. As each occurence kills the unmodified driver,
this patch makes if possible for the affected devices to function. The patch
logs only the first instance of the reset operation to prevent spamming
the logs.

Tested-by: Chris Vine <chris@cvine.freeserve.co.uk>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 drivers/net/wireless/b43/dma.c | 65 ++++++++++++++++++++++++++++++++++--------
 1 file changed, 53 insertions(+), 12 deletions(-)

--
1.8.1.2

Patch

diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index 38bc5a7..1221469 100644
--- a/drivers/net/wireless/b43/dma.c
+++ b/drivers/net/wireless/b43/dma.c
@@ -1487,8 +1487,12 @@  void b43_dma_handle_txstatus(struct b43_wldev *dev,
 	const struct b43_dma_ops *ops;
 	struct b43_dmaring *ring;
 	struct b43_dmadesc_meta *meta;
+	static const struct b43_txstatus fake; /* filled with 0 */
+	const struct b43_txstatus *txstat;
 	int slot, firstused;
 	bool frame_succeed;
+	int skip;
+	static u8 err_out1, err_out2;

 	ring = parse_cookie(dev, status->cookie, &slot);
 	if (unlikely(!ring))
@@ -1501,13 +1505,36 @@  void b43_dma_handle_txstatus(struct b43_wldev *dev,
 	firstused = ring->current_slot - ring->used_slots + 1;
 	if (firstused < 0)
 		firstused = ring->nr_slots + firstused;
+
+	skip = 0;
 	if (unlikely(slot != firstused)) {
 		/* This possibly is a firmware bug and will result in
-		 * malfunction, memory leaks and/or stall of DMA functionality. */
-		b43dbg(dev->wl, "Out of order TX status report on DMA ring %d. "
-		       "Expected %d, but got %d\n",
-		       ring->index, firstused, slot);
-		return;
+		 * malfunction, memory leaks and/or stall of DMA functionality.
+		 */
+		if (slot == next_slot(ring, next_slot(ring, firstused))) {
+			/* If a single header/data pair was missed, skip over
+			 * the first two slots in an attempt to recover.
+			 */
+			slot = firstused;
+			skip = 2;
+			if (!err_out1) {
+				/* Report the error once. */
+				b43dbg(dev->wl,
+				       "Skip on DMA ring %d slot %d.\n",
+				       ring->index, slot);
+				err_out1 = 1;
+			}
+		} else {
+			/* More than a single header/data pair were missed.
+			 * Report this error once.
+			 */
+			if (!err_out2)
+				b43dbg(dev->wl,
+				       "Out of order TX status report on DMA ring %d. Expected %d, but got %d\n",
+				       ring->index, firstused, slot);
+			err_out2 = 1;
+			return;
+		}
 	}

 	ops = ring->ops;
@@ -1522,11 +1549,13 @@  void b43_dma_handle_txstatus(struct b43_wldev *dev,
 			       slot, firstused, ring->index);
 			break;
 		}
+
 		if (meta->skb) {
 			struct b43_private_tx_info *priv_info =
-				b43_get_priv_tx_info(IEEE80211_SKB_CB(meta->skb));
+			     b43_get_priv_tx_info(IEEE80211_SKB_CB(meta->skb));

-			unmap_descbuffer(ring, meta->dmaaddr, meta->skb->len, 1);
+			unmap_descbuffer(ring, meta->dmaaddr,
+					 meta->skb->len, 1);
 			kfree(priv_info->bouncebuffer);
 			priv_info->bouncebuffer = NULL;
 		} else {
@@ -1538,8 +1567,9 @@  void b43_dma_handle_txstatus(struct b43_wldev *dev,
 			struct ieee80211_tx_info *info;

 			if (unlikely(!meta->skb)) {
-				/* This is a scatter-gather fragment of a frame, so
-				 * the skb pointer must not be NULL. */
+				/* This is a scatter-gather fragment of a frame,
+				 * so the skb pointer must not be NULL.
+				 */
 				b43dbg(dev->wl, "TX status unexpected NULL skb "
 				       "at slot %d (first=%d) on ring %d\n",
 				       slot, firstused, ring->index);
@@ -1550,9 +1580,18 @@  void b43_dma_handle_txstatus(struct b43_wldev *dev,

 			/*
 			 * Call back to inform the ieee80211 subsystem about
-			 * the status of the transmission.
+			 * the status of the transmission. When skipping over
+			 * a missed TX status report, use a status structure
+			 * filled with zeros to indicate that the frame was not
+			 * sent (frame_count 0) and not acknowledged
 			 */
-			frame_succeed = b43_fill_txstatus_report(dev, info, status);
+			if (unlikely(skip))
+				txstat = &fake;
+			else
+				txstat = status;
+
+			frame_succeed = b43_fill_txstatus_report(dev, info,
+								 txstat);
 #ifdef CONFIG_B43_DEBUG
 			if (frame_succeed)
 				ring->nr_succeed_tx_packets++;
@@ -1580,12 +1619,14 @@  void b43_dma_handle_txstatus(struct b43_wldev *dev,
 		/* Everything unmapped and free'd. So it's not used anymore. */
 		ring->used_slots--;

-		if (meta->is_last_fragment) {
+		if (meta->is_last_fragment && !skip) {
 			/* This is the last scatter-gather
 			 * fragment of the frame. We are done. */
 			break;
 		}
 		slot = next_slot(ring, slot);
+		if (skip > 0)
+			--skip;
 	}
 	if (ring->stopped) {
 		B43_WARN_ON(free_slots(ring) < TX_SLOTS_PER_FRAME);