netdev - Re: [PATCH] ixgbe: get pauseparam autoneg

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Date:	Fri, 16 Sep 2011 01:19:53 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Esa-Pekka Pyokkimies <esa-pekka.pyokkimies@...nesoft.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"mika.lansirinne@...nesoft.com" <mika.lansirinne@...nesoft.com>
Subject: Re: [PATCH] ixgbe: get pauseparam autoneg

On Thu, Sep 15, 2011 at 23:20, Esa-Pekka Pyokkimies
<esa-pekka.pyokkimies@...nesoft.com> wrote:
> There is a problem in the ixgbe driver with the reporting of the flow
> control parameters. The autoneg parameter is shown to be of if
> *either* it really is off, or current modes for both tx and rx are off.
>
> The problem is seen when the parameters are read or set when the link
> is down. In this case, the driver sees that tx and rx are currently off
> and therefore autoneg parameter is incorrectly reported to be off too.
> Also, the ethtool binary can not set the autoneg off since it sees that
> it already is. When a link later comes up, the autonegotiation is
> carried out normally and the driver later on reports the autoneg
> parameter to be on (as it is) and then it can also be changed with
> ethtool.
>
> The patch is made against v3.0 kernel, but the problem seems to be there
> since v2.6.30-rc1.
>
> Reviewer comments: What we are trying to do is to disable flow control
> while the cable is disconnected. Since ixgbe defaults to full flow
> control, we call ethtool -A autoneg off rx off tx off while the cable
> is disconnected. This doesn't work, because the driver sets
> hw->fc.current_mode = ixgbe_fc_none if the cable is unplugged.
> ixgbe_get_pauseparam() then reports to ethtool that nothing needs to be
> done. The code fixes this, but it might have some unknown consequences.
>
> Signed-off-by: Mika Lansirinne <mika.lansirinne@...nesoft.com>
> Reviewed-by: Esa-Pekka Pyokkimies <esa-pekka.pyokkimies@...nesoft.com>
> Cc: Tantilov, Emil S <emil.s.tantilov@...el.com>
> ---
> diff --git a/drivers/net/ixgbe/ixgbe_ethtool.c
> b/drivers/net/ixgbe/ixgbe_ethtool.c
> index 82d4244..db27c24 100644
> --- a/drivers/net/ixgbe/ixgbe_ethtool.c
> +++ b/drivers/net/ixgbe/ixgbe_ethtool.c
> @@ -368,13 +368,7 @@ static void ixgbe_get_pauseparam(struct net_device
> *netdev,
>        struct ixgbe_adapter *adapter = netdev_priv(netdev);
>        struct ixgbe_hw *hw = &adapter->hw;
>
> -       /*
> -        * Flow Control Autoneg isn't on if
> -        *  - we didn't ask for it OR
> -        *  - it failed, we know this by tx & rx being off
> -        */
> -       if (hw->fc.disable_fc_autoneg ||
> -           (hw->fc.current_mode == ixgbe_fc_none))
> +       if (hw->fc.disable_fc_autoneg)
>                pause->autoneg = 0;
>        else
>                pause->autoneg = 1;
> --

Thanks!  I have applied this patch to my queue.

-- 
Cheers,
Jeff
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