Patch "net: mvneta: set real interrupt per packet for tx_done" has been added to the 3.14-stable tree

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

net: mvneta: set real interrupt per packet for tx_done

to the 3.14-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-set-real-interrupt-per-packet-for-tx_done.patch
and it can be found in the queue-3.14 subdirectory.

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

From: Dmitri Epshtein <[email protected]>
Date: Wed, 6 Jul 2016 04:18:58 +0200
Subject: net: mvneta: set real interrupt per packet for tx_done

From: Dmitri Epshtein <[email protected]>

commit 06708f81528725148473c0869d6af5f809c6824b upstream.

Commit aebea2ba0f74 ("net: mvneta: fix Tx interrupt delay") intended to set coalescing threshold to a value guaranteeing interrupt generation per each sent packet, so that buffers can be released with no delay.

In fact setting threshold to '1' was wrong, because it causes interrupt every two packets. According to the documentation a reason behind it is following - interrupt occurs once sent buffers counter reaches a value, which is higher than one specified in MVNETA_TXQ_SIZE_REG(q). This behavior was confirmed during tests. Also when testing the SoC working as a NAS device, better performance was observed with int-per-packet, as it strongly depends on the fact that all transmitted packets are released immediately.

This commit enables NETA controller work in interrupt per sent packet mode by setting coalescing threshold to 0.

Fixes aebea2ba0f74 ("net: mvneta: fix Tx interrupt delay")

---
 drivers/net/ethernet/marvell/mvneta.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -213,7 +213,7 @@
 /* Various constants */
 
 /* Coalescing */
-#define MVNETA_TXDONE_COAL_PKTS		1
+#define MVNETA_TXDONE_COAL_PKTS		0	/* interrupt per packet */
 #define MVNETA_RX_COAL_PKTS		32
 #define MVNETA_RX_COAL_USEC		100
 

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

queue-3.14/net-mvneta-set-real-interrupt-per-packet-for-tx_done.patch