netdev - Re: [PATCH net v1] igc: Do not enable crosstimestamping for i225-V models

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Message-ID: <28922ca0-8513-c804-7f1d-bcce30147b68@leemhuis.info>
Date:   Tue, 14 Dec 2021 06:49:20 +0100
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        intel-wired-lan@...ts.osuosl.org
Cc:     netdev@...r.kernel.org, roots@....de, jesse.brandeburg@...el.com,
        anthony.l.nguyen@...el.com, greg@...ah.com, kuba@...nel.org
Subject: Re: [PATCH net v1] igc: Do not enable crosstimestamping for i225-V
 models

Hi, this is your Linux kernel regression tracker speaking.

Thx for working on this. Two small details:

On 14.12.21 01:39, Vinicius Costa Gomes wrote:
> It was reported that when PCIe PTM is enabled, some lockups could
> be observed with some integrated i225-V models.
> 
> While the issue is investigated, we can disable crosstimestamp for
> those models and see no loss of functionality, because those models
> don't have any support for time synchronization.
> 
> Fixes: a90ec8483732 ("igc: Add support for PTP getcrosststamp()")

That commit is in 5.15 (and Stefan is facing the problem there), hence
to make backporting explicit it's afaics better to add this line :

Cc: stable@...r.kernel.org #5.15

> Link: https://lore.kernel.org/all/924175a188159f4e03bd69908a91e606b574139b.camel@gmx.de/

Nitpicking: not sure if it's really important for anything, but to get
the proper format you afaik should do a s!/all/!/r/! to that line.

Ciao, Thorsten

> Reported-by: Stefan Dietrich <roots@....de>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> ---
>  drivers/net/ethernet/intel/igc/igc_ptp.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c b/drivers/net/ethernet/intel/igc/igc_ptp.c
> index 30568e3544cd..4f9245aa79a1 100644
> --- a/drivers/net/ethernet/intel/igc/igc_ptp.c
> +++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
> @@ -768,7 +768,20 @@ int igc_ptp_get_ts_config(struct net_device *netdev, struct ifreq *ifr)
>   */
>  static bool igc_is_crosststamp_supported(struct igc_adapter *adapter)
>  {
> -	return IS_ENABLED(CONFIG_X86_TSC) ? pcie_ptm_enabled(adapter->pdev) : false;
> +	if (!IS_ENABLED(CONFIG_X86_TSC))
> +		return false;
> +
> +	/* FIXME: it was noticed that enabling support for PCIe PTM in
> +	 * some i225-V models could cause lockups when bringing the
> +	 * interface up/down. There should be no downsides to
> +	 * disabling crosstimestamping support for i225-V, as it
> +	 * doesn't have any PTP support. That way we gain some time
> +	 * while root causing the issue.
> +	 */
> +	if (adapter->pdev->device == IGC_DEV_ID_I225_V)
> +		return false;
> +
> +	return pcie_ptm_enabled(adapter->pdev);
>  }
>  
>  static struct system_counterval_t igc_device_tstamp_to_system(u64 tstamp)
>