[Intel-wired-lan] [PATCH iwl-net v2] ixgbevf: fix link speed reporting for Hyper-V E610 VFs

On Hyper-V E610 VFs the VFLINKS register does not carry valid link speed.
Instead, link status is exposed through emulated PCI config space at offset
0x209 in VFLINKS register format. Read and decode it when checking link on
E610 VFs.

Fixes: 4c44b450c69b ("ixgbevf: Add support for Intel(R) E610 device")
Reviewed-by: Marcin Szycik <[email protected]>
Signed-off-by: Tomasz Lichwala <[email protected]>
---
 drivers/net/ethernet/intel/ixgbevf/vf.c | 79 ++++++++++++++++++++++---
 1 file changed, 70 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbevf/vf.c b/drivers/net/ethernet/intel/ixgbevf/vf.c
index f6df86d124b9..4c460ec62de3 100644
--- a/drivers/net/ethernet/intel/ixgbevf/vf.c
+++ b/drivers/net/ethernet/intel/ixgbevf/vf.c
@@ -1,14 +1,17 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright(c) 1999 - 2024 Intel Corporation. */
 
+#include <linux/unaligned.h>
+
 #include "vf.h"
 #include "ixgbevf.h"
 
-/* On Hyper-V, to reset, we need to read from this offset
- * from the PCI config space. This is the mechanism used on
- * Hyper-V to support PF/VF communication.
+/* On Hyper-V the PF/VF communication is through emulated PCI config
+ * space. The reset and link status are exposed at the offsets below.
  */
-#define IXGBE_HV_RESET_OFFSET           0x201
+#define IXGBE_HV_RESET_OFFSET		0x201
+#define IXGBE_HV_LINK_STATUS_OFFSET	0x209
+#define IXGBE_HV_LINK_STATUS_SIZE	4
 
 static inline s32 ixgbevf_write_msg_read_ack(struct ixgbe_hw *hw, u32 *msg,
 					     u32 *retmsg, u16 size)
@@ -901,6 +904,40 @@ static s32 ixgbevf_check_mac_link_vf(struct ixgbe_hw *hw,
 	return ret_val;
 }
 
+/**
+ * ixgbevf_hv_read_links_e610 - read link status from PCI config space
+ * @hw: pointer to hardware structure
+ * @links_reg: pointer to store read value
+ *
+ * On Hyper-V E610 VFs the VFLINKS register does not carry valid link speed.
+ * Instead, link status is exposed through emulated PCI config space at offset
+ * 0x209 in VFLINKS register format.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static s32 ixgbevf_hv_read_links_e610(struct ixgbe_hw *hw, u32 *links_reg)
+{
+	struct ixgbevf_adapter *adapter = hw->back;
+
+#if IS_ENABLED(CONFIG_PCI_MMCONFIG)
+	u8 data[IXGBE_HV_LINK_STATUS_SIZE];
+
+	for (int i = 0; i < IXGBE_HV_LINK_STATUS_SIZE; i++) {
+		int ret = pci_read_config_byte(adapter->pdev,
+					       IXGBE_HV_LINK_STATUS_OFFSET + i,
+					       &data[i]);
+		if (ret)
+			return pcibios_err_to_errno(ret);
+	}
+
+	*links_reg = get_unaligned_le32(data);
+	return 0;
+#else
+	dev_err_once(&adapter->pdev->dev, "cannot read link status, PCI_MMCONFIG is required for Hyper-V\n");
+	return -EOPNOTSUPP;
+#endif
+}
+
 /**
  * ixgbevf_hv_check_mac_link_vf - check link
  * @hw: pointer to private hardware struct
@@ -909,6 +946,7 @@ static s32 ixgbevf_check_mac_link_vf(struct ixgbe_hw *hw,
  * @autoneg_wait_to_complete: unused
  *
  * Hyper-V variant; there is no mailbox communication.
+ * For E610 VFs, link status is read from emulated PCI config space.
  */
 static s32 ixgbevf_hv_check_mac_link_vf(struct ixgbe_hw *hw,
 					ixgbe_link_speed *speed,
@@ -923,13 +961,30 @@ static s32 ixgbevf_hv_check_mac_link_vf(struct ixgbe_hw *hw,
 	if (!mbx->ops.check_for_rst(hw) || !mbx->timeout)
 		mac->get_link_status = true;
 
+	/* E610 VFs always read link status from emulated PCI config space
+	 * because VFLINKS does not carry valid speed for these devices.
+	 * Skip get_link_status caching since PCI config reads are cheap.
+	 */
+	if (mac->type == ixgbe_mac_e610_vf) {
+		if (ixgbevf_hv_read_links_e610(hw, &links_reg)) {
+			*link_up = false;
+			*speed = IXGBE_LINK_SPEED_UNKNOWN;
+			return 0;
+		}
+		goto decode;
+	}
+
 	if (!mac->get_link_status)
 		goto out;
 
-	/* if link status is down no point in checking to see if pf is up */
 	links_reg = IXGBE_READ_REG(hw, IXGBE_VFLINKS);
-	if (!(links_reg & IXGBE_LINKS_UP))
-		goto out;
+
+decode:
+	if (!(links_reg & IXGBE_LINKS_UP)) {
+		*link_up = false;
+		*speed = IXGBE_LINK_SPEED_UNKNOWN;
+		return 0;
+	}
 
 	/* for SFP+ modules and DA cables on 82599 it can take up to 500usecs
 	 * before the link status is correct
@@ -941,8 +996,11 @@ static s32 ixgbevf_hv_check_mac_link_vf(struct ixgbe_hw *hw,
 			udelay(100);
 			links_reg = IXGBE_READ_REG(hw, IXGBE_VFLINKS);
 
-			if (!(links_reg & IXGBE_LINKS_UP))
-				goto out;
+			if (!(links_reg & IXGBE_LINKS_UP)) {
+				*link_up = false;
+				*speed = IXGBE_LINK_SPEED_UNKNOWN;
+				return 0;
+			}
 		}
 	}
 
@@ -956,6 +1014,9 @@ static s32 ixgbevf_hv_check_mac_link_vf(struct ixgbe_hw *hw,
 	case IXGBE_LINKS_SPEED_100_82599:
 		*speed = IXGBE_LINK_SPEED_100_FULL;
 		break;
+	default:
+		*speed = IXGBE_LINK_SPEED_UNKNOWN;
+		break;
 	}
 
 	/* if we passed all the tests above then the link is up and we no
-- 
2.54.0