[PATCH 4.9 20/25] igb: skip phy status check where unavailable

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Kevin Mitchell <kevmitch@arista.com>

[ Upstream commit 942d2ad5d2e0df758a645ddfadffde2795322728 ]

igb_read_phy_reg() will silently return, leaving phy_data untouched, if
hw->ops.read_reg isn't set. Depending on the uninitialized value of
phy_data, this led to the phy status check either succeeding immediately
or looping continuously for 2 seconds before emitting a noisy err-level
timeout. This message went out to the console even though there was no
actual problem.

Instead, first check if there is read_reg function pointer. If not,
proceed without trying to check the phy status register.

Fixes: b72f3f72005d ("igb: When GbE link up, wait for Remote receiver status condition")
Signed-off-by: Kevin Mitchell <kevmitch@arista.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 6bede6774486..d825e527ec1a 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -4546,7 +4546,8 @@ static void igb_watchdog_task(struct work_struct *work)
 				break;
 			}
 
-			if (adapter->link_speed != SPEED_1000)
+			if (adapter->link_speed != SPEED_1000 ||
+			    !hw->phy.ops.read_reg)
 				goto no_wait;
 
 			/* wait for Remote receiver status OK */
-- 
2.35.1