Patch "net: mvneta: fix handling of the Tx descriptor counter" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

net: mvneta: fix handling of the Tx descriptor counter

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-mvneta-fix-handling-of-the-tx-descriptor-counter.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Simon Guinot <[email protected]>
Date: Mon, 13 Nov 2017 16:27:02 +0100
Subject: net: mvneta: fix handling of the Tx descriptor counter

From: Simon Guinot <[email protected]>

commit 0d63785c6b94b5d2f095f90755825f90eea791f5 upstream.

The mvneta controller provides a 8-bit register to update the pending Tx descriptor counter. Then, a maximum of 255 Tx descriptors can be added at once. In the current code the mvneta_txq_pend_desc_add function assumes the caller takes care of this limit. But it is not the case. In some situations (xmit_more flag), more than 255 descriptors are added. When this happens, the Tx descriptor counter register is updated with a wrong value, which breaks the whole Tx queue management.

This patch fixes the issue by allowing the mvneta_txq_pend_desc_add function to process more than 255 Tx descriptors.

---
 drivers/net/ethernet/marvell/mvneta.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

@@ -816,11 +816,14 @@ static void mvneta_txq_pend_desc_add(str
 {
 	u32 val;
 
-	/* Only 255 descriptors can be added at once ; Assume caller
-	 * process TX desriptors in quanta less than 256
-	 */
-	val = pend_desc + txq->pending;
-	mvreg_write(pp, MVNETA_TXQ_UPDATE_REG(txq->id), val);
+	pend_desc += txq->pending;
+
+	/* Only 255 Tx descriptors can be added at once */
+	do {
+		val = min(pend_desc, 255);
+		mvreg_write(pp, MVNETA_TXQ_UPDATE_REG(txq->id), val);
+		pend_desc -= val;
+	} while (pend_desc > 0);
 	txq->pending = 0;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/net-mvneta-fix-handling-of-the-tx-descriptor-counter.patch