netdev - [net 1/2] e1000e: Correct link check logic for 82571 serdes

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Date:	Sat, 14 Jul 2012 01:34:05 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	davem@...emloft.net
Cc:	Tushar Dave <tushar.n.dave@...el.com>, netdev@...r.kernel.org,
	gospo@...hat.com, sassmann@...hat.com, stable@...r.kernel.org,
	dnelson@...hat.com, bruce.w.allan@...el.com,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [net 1/2] e1000e: Correct link check logic for 82571 serdes

From: Tushar Dave <tushar.n.dave@...el.com>

SYNCH bit and IV bit of RXCW register are sticky. Before examining these bits,
RXCW should be read twice to filter out one-time false events and have correct
values for these bits. Incorrect values of these bits in link check logic can
cause weird link stability issues if auto-negotiation fails.

CC: stable <stable@...r.kernel.org> [2.6.38+]
Reported-by: Dean Nelson <dnelson@...hat.com>
Signed-off-by: Tushar Dave <tushar.n.dave@...el.com>
Reviewed-by: Bruce Allan <bruce.w.allan@...el.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
---
 drivers/net/ethernet/intel/e1000e/82571.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/intel/e1000e/82571.c b/drivers/net/ethernet/intel/e1000e/82571.c
index 36db4df..1f063dc 100644
--- a/drivers/net/ethernet/intel/e1000e/82571.c
+++ b/drivers/net/ethernet/intel/e1000e/82571.c
@@ -1572,6 +1572,9 @@ static s32 e1000_check_for_serdes_link_82571(struct e1000_hw *hw)
 	ctrl = er32(CTRL);
 	status = er32(STATUS);
 	rxcw = er32(RXCW);
+	/* SYNCH bit and IV bit are sticky */
+	udelay(10);
+	rxcw = er32(RXCW);
 
 	if ((rxcw & E1000_RXCW_SYNCH) && !(rxcw & E1000_RXCW_IV)) {
 
-- 
1.7.10.4

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