ACK: [PATCH 1/1] igb: Report speed and duplex as unknown when device is runtime suspended

[Kleber Souza]

On 2020-05-26 09:16, Kai-Heng Feng wrote:
> BugLink: https://bugs.launchpad.net/bugs/1880656
> 
> igb device gets runtime suspended when there's no link partner. We can't
> get correct speed under that state:
> $ cat /sys/class/net/enp3s0/speed
> 1000
> 
> In addition to that, an error can also be spotted in dmesg:
> [  385.991957] igb 0000:03:00.0 enp3s0: PCIe link lost
> 
> Since device can only be runtime suspended when there's no link partner,
> we can skip reading register and let the following logic set speed and
> duplex with correct status.
> 
> The more generic approach will be wrap get_link_ksettings() with begin()
> and complete() callbacks. However, for this particular issue, begin()
> calls igb_runtime_resume() , which tries to rtnl_lock() while the lock
> is already hold by upper ethtool layer.
> 
> So let's take this approach until the igb_runtime_resume() no longer
> needs to hold rtnl_lock.
> 
> CC: stable <stable at vger.kernel.org>
> Suggested-by: Alexander Duyck <alexander.duyck at gmail.com>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
> Tested-by: Aaron Brown <aaron.f.brown at intel.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher at intel.com>
> (cherry picked from commit 165ae7a8feb53dc47fb041357e4b253bfc927cf9 linux-next)
> Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

> ---
>  drivers/net/ethernet/intel/igb/igb_ethtool.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb_ethtool.c b/drivers/net/ethernet/intel/igb/igb_ethtool.c
> index 39d3b76a6f5d..2cd003c5ad43 100644
> --- a/drivers/net/ethernet/intel/igb/igb_ethtool.c
> +++ b/drivers/net/ethernet/intel/igb/igb_ethtool.c
> @@ -143,7 +143,8 @@ static int igb_get_link_ksettings(struct net_device *netdev,
>  	u32 speed;
>  	u32 supported, advertising;
>  
> -	status = rd32(E1000_STATUS);
> +	status = pm_runtime_suspended(&adapter->pdev->dev) ?
> +		 0 : rd32(E1000_STATUS);
>  	if (hw->phy.media_type == e1000_media_type_copper) {
>  
>  		supported = (SUPPORTED_10baseT_Half |
>