netdev - [PATCH v1 iwl-net] igc: power up PHY before link test

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Message-ID: <20250830170656.61496-1-enjuk@amazon.com>
Date: Sun, 31 Aug 2025 02:06:19 +0900
From: Kohei Enju <enjuk@...zon.com>
To: <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>
CC: Tony Nguyen <anthony.l.nguyen@...el.com>, Przemek Kitszel
	<przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Vitaly Lifshits
	<vitaly.lifshits@...el.com>, <kohei.enju@...il.com>, Kohei Enju
	<enjuk@...zon.com>
Subject: [PATCH v1 iwl-net] igc: power up PHY before link test

The current implementation of igc driver doesn't power up PHY before
link test in igc_ethtool_diag_test(), causing the link test to always
report FAIL when admin state is down and PHY is consequently powered
down.

To test the link state regardless of admin state, let's power up PHY in
case of PHY down before link test.

Tested on Intel Corporation Ethernet Controller I226-V (rev 04) with
cable connected and link available.

Set device down and do ethtool test.
  # ip link set dev enp0s5 down

Without patch:
  # ethtool --test enp0s5
  The test result is FAIL
  The test extra info:
  Register test  (offline)         0
  Eeprom test    (offline)         0
  Interrupt test (offline)         0
  Loopback test  (offline)         0
  Link test   (on/offline)         1

With patch:
  # ethtool --test enp0s5
  The test result is PASS
  The test extra info:
  Register test  (offline)         0
  Eeprom test    (offline)         0
  Interrupt test (offline)         0
  Loopback test  (offline)         0
  Link test   (on/offline)         0

Fixes: f026d8ca2904 ("igc: add support to eeprom, registers and link self-tests")
Signed-off-by: Kohei Enju <enjuk@...zon.com>
---
This patch uses igc_power_up_phy_copper() instead of igc_power_up_link()
to avoid PHY reset. The function only clears MII_CR_POWER_DOWN bit
without performing PHY reset, so it should not cause the autoneg
interference issue explained in the following comment:
    /* Link test performed before hardware reset so autoneg doesn't
     * interfere with test result
     */
---
 drivers/net/ethernet/intel/igc/igc_ethtool.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/intel/igc/igc_ethtool.c b/drivers/net/ethernet/intel/igc/igc_ethtool.c
index f3e7218ba6f3..ca93629b1d3a 100644
--- a/drivers/net/ethernet/intel/igc/igc_ethtool.c
+++ b/drivers/net/ethernet/intel/igc/igc_ethtool.c
@@ -2094,6 +2094,9 @@ static void igc_ethtool_diag_test(struct net_device *netdev,
 		netdev_info(adapter->netdev, "Offline testing starting");
 		set_bit(__IGC_TESTING, &adapter->state);
 
+		/* power up PHY for link test */
+		igc_power_up_phy_copper(&adapter->hw);
+
 		/* Link test performed before hardware reset so autoneg doesn't
 		 * interfere with test result
 		 */
-- 
2.48.1