Re: [PATCH net 3/3] igc: return early when failing to read EECD register

[Tony Nguyen <anthony.l.nguyen@intel.com>]

On 4/18/2025 12:34 PM, Bjorn Helgaas wrote:
> [+cc Kalesh, Przemek, linux-pci]
> 
> On Tue, Jan 07, 2025 at 11:01:47AM -0800, Tony Nguyen wrote:
>> From: En-Wei Wu <en-wei.wu@canonical.com>
>>
>> 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@canonical.com>
>> Signed-off-by: En-Wei Wu <en-wei.wu@canonical.com>
>> Reviewed-by: Vitaly Lifshits <vitaly.lifshits@intel.com>
>> Tested-by: Mor Bar-Gabay <morx.bar.gabay@intel.com>
>> Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
>> ---
>>   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;
> 
> I don't understand this.  It looks like a band-aid that makes boot
> faster but doesn't solve the real problem.
> 
> In its defense, I guess that with this patch, the first igc probe
> fails, and then for some reason we attempt another a few seconds
> later, and the second igc probe works fine, so the NIC actually does
> end up working correct, right?
> 
> I think the PCI core has some issues with configuring ASPM L1.2, and I
> wonder if those are relevant here.  If somebody can repro the problem
> (i.e., without this patch, which looks like it appeared in v6.13 as
> bd2776e39c2a ("igc: return early when failing to read EECD
> register")), I wonder if you could try booting with "pcie_port_pm=off
> pcie_aspm.policy=performance" and see if that also avoids the problem?
> 
> If so, I'd like to see the dmesg log with "pci=earlydump" and the
> "sudo lspci -vv" output when booted with and without "pcie_port_pm=off
> pcie_aspm.policy=performance".

We weren't able to get a repro here.

En-Wei would you be able to provide this to Bjorn?

Thanks,
Tony

>>   	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);
>> -- 
>> 2.47.1
>>