[PATCH v3 4/7] e1000e: Add Dell's Comet Lake systems into S0ix heuristics

[Mario Limonciello]

Dell's shipping Comet Lake Latitude and Precision systems containing i219LM are
properly configured and should use the S0ix flows.

Disabling s0ix entry and exit flows caused a regression in power consumption
over suspend to idle on these systems.

Fixes: e086ba2fccda ("e1000e: disable s0ix entry and exit flows for ME systems")
Tested-by: Yijun Shen <yijun.s...@dell.com>
Signed-off-by: Mario Limonciello <mario.limoncie...@dell.com>
---
 drivers/net/ethernet/intel/e1000e/s0ix.c | 33 +++++++++++++++++++++---
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/s0ix.c 
b/drivers/net/ethernet/intel/e1000e/s0ix.c
index c3013edbd9e4..74043e80c32f 100644
--- a/drivers/net/ethernet/intel/e1000e/s0ix.c
+++ b/drivers/net/ethernet/intel/e1000e/s0ix.c
@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
-/* Copyright(c) 1999 - 2018 Intel Corporation. */
+/* Copyright(c) 1999 - 2018 Intel Corporation.
+ * Copyright(c) 2020 Dell Inc.
+ */
 
 #include <linux/netdevice.h>
 
@@ -44,6 +46,26 @@ static bool e1000e_check_me(u16 device_id)
        return false;
 }
 
+static bool e1000e_check_subsystem_allowlist(struct pci_dev *dev)
+{
+       if (dev->subsystem_vendor == PCI_VENDOR_ID_DELL) {
+               switch (dev->subsystem_device) {
+               case 0x099f: /* Latitude 5310 */
+               case 0x09a0: /* Latitude 5410 */
+               case 0x09c9: /* Latitude 5410 */
+               case 0x09a1: /* Latitude 5510 */
+               case 0x09a2: /* Precision 3550 */
+               case 0x09c0: /* Latitude 5411 */
+               case 0x09c1: /* Latitude 5511 */
+               case 0x09c2: /* Precision 3551 */
+               case 0x09c3: /* Precision 7550 */
+               case 0x09c4: /* Precision 7750 */
+                       return true;
+               }
+       }
+       return false;
+}
+
 void e1000e_s0ix_entry_flow(struct e1000_adapter *adapter)
 {
        struct e1000_hw *hw = &adapter->hw;
@@ -273,8 +295,11 @@ void e1000e_maybe_enable_s0ix(struct e1000_adapter 
*adapter)
        /* require cannon point or later */
        if (hw->mac.type < e1000_pch_cnp)
                return;
-       /* turn off on ME configurations */
-       if (e1000e_check_me(pdev->device))
-               return;
+       /* check for allowlist of systems */
+       if (!e1000e_check_subsystem_allowlist(pdev)) {
+               /* turn off on ME configurations */
+               if (e1000e_check_me(pdev->device))
+                       return;
+       }
        adapter->flags2 |= FLAG2_ENABLE_S0IX_FLOWS;
 }
-- 
2.25.1