netdev - [PATCH net 3/3] igc: disable L1.2 PCI-E link substate to avoid performance issue

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Message-ID: <20250701164317.2983952-4-anthony.l.nguyen@intel.com>
Date: Tue,  1 Jul 2025 09:43:15 -0700
From: Tony Nguyen <anthony.l.nguyen@...el.com>
To: davem@...emloft.net,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com,
	andrew+netdev@...n.ch,
	netdev@...r.kernel.org
Cc: Vitaly Lifshits <vitaly.lifshits@...el.com>,
	anthony.l.nguyen@...el.com,
	dima.ruinskiy@...el.com,
	Aleksandr Loktionov <aleksandr.loktionov@...el.com>,
	Mor Bar-Gabay <morx.bar.gabay@...el.com>
Subject: [PATCH net 3/3] igc: disable L1.2 PCI-E link substate to avoid performance issue

From: Vitaly Lifshits <vitaly.lifshits@...el.com>

I226 devices advertise support for the PCI-E link L1.2 substate. However,
due to a hardware limitation, the exit latency from this low-power state
is longer than the packet buffer can tolerate under high traffic
conditions. This can lead to packet loss and degraded performance.

To mitigate this, disable the L1.2 substate. The increased power draw
between L1.1 and L1.2 is insignificant.

Fixes: 43546211738e ("igc: Add new device ID's")
Link: https://lore.kernel.org/intel-wired-lan/15248b4f-3271-42dd-8e35-02bfc92b25e1@intel.com
Signed-off-by: Vitaly Lifshits <vitaly.lifshits@...el.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@...el.com>
Tested-by: Mor Bar-Gabay <morx.bar.gabay@...el.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
---
 drivers/net/ethernet/intel/igc/igc_main.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 686793c539f2..031c332f66c4 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -7115,6 +7115,10 @@ static int igc_probe(struct pci_dev *pdev,
 	adapter->port_num = hw->bus.func;
 	adapter->msg_enable = netif_msg_init(debug, DEFAULT_MSG_ENABLE);
 
+	/* Disable ASPM L1.2 on I226 devices to avoid packet loss */
+	if (igc_is_device_id_i226(hw))
+		pci_disable_link_state(pdev, PCIE_LINK_STATE_L1_2);
+
 	err = pci_save_state(pdev);
 	if (err)
 		goto err_ioremap;
@@ -7500,6 +7504,9 @@ static int __igc_resume(struct device *dev, bool rpm)
 	pci_enable_wake(pdev, PCI_D3hot, 0);
 	pci_enable_wake(pdev, PCI_D3cold, 0);
 
+	if (igc_is_device_id_i226(hw))
+		pci_disable_link_state(pdev, PCIE_LINK_STATE_L1_2);
+
 	if (igc_init_interrupt_scheme(adapter, true)) {
 		netdev_err(netdev, "Unable to allocate memory for queues\n");
 		return -ENOMEM;
@@ -7625,6 +7632,9 @@ static pci_ers_result_t igc_io_slot_reset(struct pci_dev *pdev)
 		pci_enable_wake(pdev, PCI_D3hot, 0);
 		pci_enable_wake(pdev, PCI_D3cold, 0);
 
+		if (igc_is_device_id_i226(hw))
+			pci_disable_link_state_locked(pdev, PCIE_LINK_STATE_L1_2);
+
 		/* In case of PCI error, adapter loses its HW address
 		 * so we should re-assign it here.
 		 */
-- 
2.47.1