igb: Disable the BMC-to-OS Watchdog Enable bit for DMAC.

Under certain scenarios, it's possible that bursty manageability traffic
over the BMC-to-OS path may overrun the internal manageability receive
buffer causing dropped manageability packets. Clearing this bit prevents
this situation by interrupting coalescing to allow manageability traffic
through.

Signed-off-by: Matthew Vick <matthew.vick@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

2 files changed, 5 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/igb/e1000_defines.h b/drivers/net/ethernet/intel/igb/e1000_defines.h
index 6409f85632f5..ec7e4fe3e3ee 100644
--- a/drivers/net/ethernet/intel/igb/e1000_defines.h
+++ b/drivers/net/ethernet/intel/igb/e1000_defines.h
@@ -301,6 +301,8 @@
                                                         * transactions */
 #define E1000_DMACR_DMAC_LX_SHIFT       28
 #define E1000_DMACR_DMAC_EN             0x80000000 /* Enable DMA Coalescing */
+/* DMA Coalescing BMC-to-OS Watchdog Enable */
+#define E1000_DMACR_DC_BMC2OSW_EN       0x00008000
 
 #define E1000_DMCTXTH_DMCTTHR_MASK      0x00000FFF /* DMA Coalescing Transmit
                                                         * Threshold */
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 9bbf1a275947..dd3bfe8cd36c 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -7147,6 +7147,9 @@ static void igb_init_dmac(struct igb_adapter *adapter, u32 pba)
 
                         /* watchdog timer= +-1000 usec in 32usec intervals */
                         reg |= (1000 >> 5);
+
+                        /* Disable BMC-to-OS Watchdog Enable */
+                        reg &= ~E1000_DMACR_DC_BMC2OSW_EN;
                         wr32(E1000_DMACR, reg);
 
                         /*