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

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Message-ID: <b0e073bd-dc1f-4af9-9f7b-63b4b726c585@intel.com>
Date: Thu, 26 Dec 2024 15:35:24 +0200
From: Mor Bar-Gabay <morx.bar.gabay@...el.com>
To: En-Wei Wu <en-wei.wu@...onical.com>, <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: Re: [Intel-wired-lan] [PATCH iwl-net v2] igc: return early when
 failing to read EECD register

On 18/12/2024 4:37, En-Wei Wu wrote:
> 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>
> Reviewed-by: Vitaly Lifshits <vitaly.lifshits@...el.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(+)
> 
Tested-by: Mor Bar-Gabay <morx.bar.gabay@...el.com>