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

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Message-ID: <4d6cc03c-1190-4ed5-9afe-9062fdde35b0@intel.com>
Date: Sun, 22 Dec 2024 10:54:29 +0200
From: "Lifshits, Vitaly" <vitaly.lifshits@...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: Chia-Lin Kao <acelan.kao@...onical.com>
Subject: Re: [PATCH iwl-net v2] igc: return early when failing to read EECD
 register



On 12/18/2024 4:37 AM, 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(+)
> 
> 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);