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

[Mor Bar-Gabay]

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 at canonical.com>
> Signed-off-by: En-Wei Wu <en-wei.wu at canonical.com>
> Reviewed-by: Vitaly Lifshits <vitaly.lifshits at intel.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 at intel.com>