e1000e: disable far-end loopback mode on ESB2

The ESB2 LAN includes a debug feature that enables far-end loopback (FELB)
of the SerDes/Kumeran interface.  This feature is activated when receiving
a sequence of symbols that includes a reserved codeword.  On a perfect
link, FELB would never be activated.  In the presence of bit errors, there
is a very small, but non-zero, probability of FELB being activated.

If the FELB is activated, the SerDes link becomes non-functional and must
be reset.  It could also corrupt the switching tables in the switch since
the ESB2 is transmitting packets with a different source MAC address.

This patch disables the FELB feature.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

2 files changed, 9 insertions, 0 deletions

diff --git a/drivers/net/e1000e/es2lan.c b/drivers/net/e1000e/es2lan.c
index f4bbeb22f51f..c0ecb2d9fdb7 100644
--- a/drivers/net/e1000e/es2lan.c
+++ b/drivers/net/e1000e/es2lan.c
@@ -836,6 +836,7 @@ static s32 e1000_init_hw_80003es2lan(struct e1000_hw *hw)
         struct e1000_mac_info *mac = &hw->mac;
         u32 reg_data;
         s32 ret_val;
+        u16 kum_reg_data;
         u16 i;
 
         e1000_initialize_hw_bits_80003es2lan(hw);
@@ -861,6 +862,13 @@ static s32 e1000_init_hw_80003es2lan(struct e1000_hw *hw)
         /* Setup link and flow control */
         ret_val = e1000e_setup_link(hw);
 
+        /* Disable IBIST slave mode (far-end loopback) */
+        e1000_read_kmrn_reg_80003es2lan(hw, E1000_KMRNCTRLSTA_INBAND_PARAM,
+                                        &kum_reg_data);
+        kum_reg_data |= E1000_KMRNCTRLSTA_IBIST_DISABLE;
+        e1000_write_kmrn_reg_80003es2lan(hw, E1000_KMRNCTRLSTA_INBAND_PARAM,
+                                         kum_reg_data);
+
         /* Set the transmit descriptor write-back policy */
         reg_data = er32(TXDCTL(0));
         reg_data = (reg_data & ~E1000_TXDCTL_WTHRESH) |
diff --git a/drivers/net/e1000e/hw.h b/drivers/net/e1000e/hw.h
index 6c2fa8327f5c..dde584f5ccc7 100644
--- a/drivers/net/e1000e/hw.h
+++ b/drivers/net/e1000e/hw.h
@@ -312,6 +312,7 @@ enum e1e_registers {
 #define E1000_KMRNCTRLSTA_DIAG_OFFSET   0x3    /* Kumeran Diagnostic */
 #define E1000_KMRNCTRLSTA_TIMEOUTS      0x4    /* Kumeran Timeouts */
 #define E1000_KMRNCTRLSTA_INBAND_PARAM  0x9    /* Kumeran InBand Parameters */
+#define E1000_KMRNCTRLSTA_IBIST_DISABLE 0x0200 /* Kumeran IBIST Disable */
 #define E1000_KMRNCTRLSTA_DIAG_NELPBK   0x1000 /* Nearend Loopback mode */
 #define E1000_KMRNCTRLSTA_K1_CONFIG     0x7
 #define E1000_KMRNCTRLSTA_K1_ENABLE     0x0002