[PATCH] igc: Return early when failing to read EECD register

[Chia-Lin Kao (AceLan)]

When booting with a dock connected, the igc driver can get stuck for ~40
seconds if PCIe link is lost during initialization.

This happens because the driver access device after EECD register reads
return all F's, indicating failed reads. Consequently, hw->hw_addr is set
to NULL, which impacts subsequent rd32() reads. This leads to the driver
hanging in igc_get_hw_semaphore_i225(), as the invalid hw->hw_addr
prevents retrieving the expected value.

To address this, a validation check is added for the EECD register read
result. If all F's are returned, indicating PCIe link loss, the driver
will return -ENXIO immediately. This avoids the 40-second hang and
significantly improves boot time when using a dock with an igc NIC.

[    0.911913] igc 0000:70:00.0: enabling device (0000 -> 0002)
[    0.912386] igc 0000:70:00.0: PTM enabled, 4ns granularity
[    1.571098] igc 0000:70:00.0 (unnamed net_device) (uninitialized): PCIe link lost, device now detached
[   43.449095] igc_get_hw_semaphore_i225: igc 0000:70:00.0 (unnamed net_device) (uninitialized): Driver can't access device - SMBI bit is set.
[   43.449186] igc 0000:70:00.0: probe with driver igc failed with error -13
[   46.345701] igc 0000:70:00.0: enabling device (0000 -> 0002)
[   46.345777] igc 0000:70:00.0: PTM enabled, 4ns granularity

Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@xxxxxxxxxxxxx>
---
 drivers/net/ethernet/intel/igc/igc_base.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/intel/igc/igc_base.c b/drivers/net/ethernet/intel/igc/igc_base.c
index 9fae8bdec2a7..54ce60280765 100644
--- a/drivers/net/ethernet/intel/igc/igc_base.c
+++ b/drivers/net/ethernet/intel/igc/igc_base.c
@@ -68,6 +68,10 @@ static s32 igc_init_nvm_params_base(struct igc_hw *hw)
 	u32 eecd = rd32(IGC_EECD);
 	u16 size;
 
+	/* failed to read reg and got all F's */
+	if (!(~eecd))
+		return -ENODEV;
+
 	size = FIELD_GET(IGC_EECD_SIZE_EX_MASK, eecd);
 
 	/* Added to a constant, "size" becomes the left-shift value
-- 
2.43.0