netdev - Patch "net: ethernet: pcnet32: Setup the SRAM and NOUFLO on Am79C97{3, 5}" has been added to the 3.10-stable tree

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Date:	Fri, 10 Apr 2015 15:12:20 +0200
From:	<gregkh@...uxfoundation.org>
To:	markos.chandras@...tec.com, davem@...emloft.net,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, pcnet32@...ntier.com
Cc:	<stable@...r.kernel.org>, <stable-commits@...r.kernel.org>
Subject: Patch "net: ethernet: pcnet32: Setup the SRAM and NOUFLO on Am79C97{3, 5}" has been added to the 3.10-stable tree


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

    net: ethernet: pcnet32: Setup the SRAM and NOUFLO on Am79C97{3, 5}

to the 3.10-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-ethernet-pcnet32-setup-the-sram-and-nouflo-on-am79c97-3-5.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@...r.kernel.org> know about it.


>From 87f966d97b89774162df04d2106c6350c8fe4cb3 Mon Sep 17 00:00:00 2001
From: Markos Chandras <markos.chandras@...tec.com>
Date: Thu, 19 Mar 2015 10:28:14 +0000
Subject: net: ethernet: pcnet32: Setup the SRAM and NOUFLO on Am79C97{3, 5}

From: Markos Chandras <markos.chandras@...tec.com>

commit 87f966d97b89774162df04d2106c6350c8fe4cb3 upstream.

On a MIPS Malta board, tons of fifo underflow errors have been observed
when using u-boot as bootloader instead of YAMON. The reason for that
is that YAMON used to set the pcnet device to SRAM mode but u-boot does
not. As a result, the default Tx threshold (64 bytes) is now too small to
keep the fifo relatively used and it can result to Tx fifo underflow errors.
As a result of which, it's best to setup the SRAM on supported controllers
so we can always use the NOUFLO bit.

Cc: <netdev@...r.kernel.org>
Cc: <linux-kernel@...r.kernel.org>
Cc: Don Fry <pcnet32@...ntier.com>
Signed-off-by: Markos Chandras <markos.chandras@...tec.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/net/ethernet/amd/pcnet32.c |   31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/amd/pcnet32.c
+++ b/drivers/net/ethernet/amd/pcnet32.c
@@ -1516,7 +1516,7 @@ pcnet32_probe1(unsigned long ioaddr, int
 {
 	struct pcnet32_private *lp;
 	int i, media;
-	int fdx, mii, fset, dxsuflo;
+	int fdx, mii, fset, dxsuflo, sram;
 	int chip_version;
 	char *chipname;
 	struct net_device *dev;
@@ -1553,7 +1553,7 @@ pcnet32_probe1(unsigned long ioaddr, int
 	}
 
 	/* initialize variables */
-	fdx = mii = fset = dxsuflo = 0;
+	fdx = mii = fset = dxsuflo = sram = 0;
 	chip_version = (chip_version >> 12) & 0xffff;
 
 	switch (chip_version) {
@@ -1586,6 +1586,7 @@ pcnet32_probe1(unsigned long ioaddr, int
 		chipname = "PCnet/FAST III 79C973";	/* PCI */
 		fdx = 1;
 		mii = 1;
+		sram = 1;
 		break;
 	case 0x2626:
 		chipname = "PCnet/Home 79C978";	/* PCI */
@@ -1609,6 +1610,7 @@ pcnet32_probe1(unsigned long ioaddr, int
 		chipname = "PCnet/FAST III 79C975";	/* PCI */
 		fdx = 1;
 		mii = 1;
+		sram = 1;
 		break;
 	case 0x2628:
 		chipname = "PCnet/PRO 79C976";
@@ -1637,6 +1639,31 @@ pcnet32_probe1(unsigned long ioaddr, int
 		dxsuflo = 1;
 	}
 
+	/*
+	 * The Am79C973/Am79C975 controllers come with 12K of SRAM
+	 * which we can use for the Tx/Rx buffers but most importantly,
+	 * the use of SRAM allow us to use the BCR18:NOUFLO bit to avoid
+	 * Tx fifo underflows.
+	 */
+	if (sram) {
+		/*
+		 * The SRAM is being configured in two steps. First we
+		 * set the SRAM size in the BCR25:SRAM_SIZE bits. According
+		 * to the datasheet, each bit corresponds to a 512-byte
+		 * page so we can have at most 24 pages. The SRAM_SIZE
+		 * holds the value of the upper 8 bits of the 16-bit SRAM size.
+		 * The low 8-bits start at 0x00 and end at 0xff. So the
+		 * address range is from 0x0000 up to 0x17ff. Therefore,
+		 * the SRAM_SIZE is set to 0x17. The next step is to set
+		 * the BCR26:SRAM_BND midway through so the Tx and Rx
+		 * buffers can share the SRAM equally.
+		 */
+		a->write_bcr(ioaddr, 25, 0x17);
+		a->write_bcr(ioaddr, 26, 0xc);
+		/* And finally enable the NOUFLO bit */
+		a->write_bcr(ioaddr, 18, a->read_bcr(ioaddr, 18) | (1 << 11));
+	}
+
 	dev = alloc_etherdev(sizeof(*lp));
 	if (!dev) {
 		ret = -ENOMEM;


Patches currently in stable-queue which might be from markos.chandras@...tec.com are

queue-3.10/net-ethernet-pcnet32-setup-the-sram-and-nouflo-on-am79c97-3-5.patch
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