linux-kernel - [PATCH iwl-net v2] igc: return early when failing to read EECD register

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Message-ID: <20241218023742.882811-1-en-wei.wu@canonical.com>
Date: Wed, 18 Dec 2024 10:37:42 +0800
From: En-Wei Wu <en-wei.wu@...onical.com>
To: anthony.l.nguyen@...el.com,
	przemyslaw.kitszel@...el.com,
	andrew+netdev@...n.ch,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	intel-wired-lan@...ts.osuosl.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: vitaly.lifshits@...el.com,
	Chia-Lin Kao <acelan.kao@...onical.com>
Subject: [PATCH iwl-net v2] igc: return early when failing to read EECD register

When booting with a dock connected, the igc driver may 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 and a corresponding return value
catch 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.

Log before the patch:
[    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

Log after the patch:
[    1.031000] igc 0000:70:00.0: enabling device (0000 -> 0002)
[    1.032097] igc 0000:70:00.0: PTM enabled, 4ns granularity
[    1.642291] igc 0000:70:00.0 (unnamed net_device) (uninitialized): PCIe link lost, device now detached
[    5.480490] igc 0000:70:00.0: enabling device (0000 -> 0002)
[    5.480516] igc 0000:70:00.0: PTM enabled, 4ns granularity

Fixes: ab4056126813 ("igc: Add NVM support")
Cc: Chia-Lin Kao (AceLan) <acelan.kao@...onical.com>
Signed-off-by: En-Wei Wu <en-wei.wu@...onical.com>
---
Changes in v2:
- Added "after" logs showing improved boot time
- Fixed error code (use -ENXIO instead of -ENODEV)
- Added error propagation in igc_get_invariants_base()
- Added Fixes tag
- Added [PATCH iwl-net] prefix
- Changed original author from AceLan to En-Wei

 drivers/net/ethernet/intel/igc/igc_base.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/intel/igc/igc_base.c b/drivers/net/ethernet/intel/igc/igc_base.c
index 9fae8bdec2a7..1613b562d17c 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 -ENXIO;
+
 	size = FIELD_GET(IGC_EECD_SIZE_EX_MASK, eecd);
 
 	/* Added to a constant, "size" becomes the left-shift value
@@ -221,6 +225,8 @@ static s32 igc_get_invariants_base(struct igc_hw *hw)
 
 	/* NVM initialization */
 	ret_val = igc_init_nvm_params_base(hw);
+	if (ret_val)
+		goto out;
 	switch (hw->mac.type) {
 	case igc_i225:
 		ret_val = igc_init_nvm_params_i225(hw);
-- 
2.43.0