linux-kernel - [PATCH 4.14 125/178] net: dsa: lan9303: Do not disable switch fabric port 0 at .probe

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Message-Id: <20171218152926.004793580@linuxfoundation.org>
Date:   Mon, 18 Dec 2017 16:49:21 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Egil Hjelmeland <privat@...l-hjelmeland.no>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 125/178] net: dsa: lan9303: Do not disable switch fabric port 0 at .probe

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Egil Hjelmeland <privat@...l-hjelmeland.no>

[ Upstream commit 3c91b0c1de8d013490bbc41ce9ee8810ea5baddd ]

Make the LAN9303 work when lan9303_probe() is called twice.

For some unknown reason the LAN9303 switch fail to forward data when switch
fabric port 0 TX is disabled during probe. (Write of LAN9303_MAC_TX_CFG_0
in lan9303_disable_processing_port().)

In that situation the switch fabric seem to receive frames, because the ALR
is learning addresses. But no frames are transmitted on any of the ports.

In our system lan9303_probe() is called twice, first time
dsa_register_switch() return -EPROBE_DEFER. As an experiment, modified the
code to skip writing LAN9303_MAC_TX_CFG_0, port 0 during the first probe.
Then the switch works as expected.

Resolve the problem by not calling lan9303_disable_processing_port() on
port 0 during probe. Ports 1 and 2 are still disabled.

Although unsatisfying that the exact failure mechanism is not known,
the patch should not cause any harm.

Signed-off-by: Egil Hjelmeland <privat@...l-hjelmeland.no>
Reviewed-by: Andrew Lunn <andrew@...n.ch>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/dsa/lan9303-core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/dsa/lan9303-core.c
+++ b/drivers/net/dsa/lan9303-core.c
@@ -569,7 +569,7 @@ static int lan9303_disable_processing(st
 {
 	int p;

-	for (p = 0; p < LAN9303_NUM_PORTS; p++) {
+	for (p = 1; p < LAN9303_NUM_PORTS; p++) {
 		int ret = lan9303_disable_processing_port(chip, p);

 		if (ret)