netdev - Re: [PATCH net-next 08/10] r8169: remove rtl8169_set_speed

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Message-ID: <c2d3f0d0-3082-a96a-3dbb-02d9a90117a7@gmail.com>
Date:   Wed, 4 Jul 2018 20:13:05 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     David Miller <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 08/10] r8169: remove rtl8169_set_speed_xmii

On 04.07.2018 16:46, Andrew Lunn wrote:
> On Mon, Jul 02, 2018 at 11:54:54PM +0200, Heiner Kallweit wrote:
>> On 02.07.2018 23:21, Andrew Lunn wrote:
>>>> -		auto_nego |= ADVERTISE_PAUSE_CAP | ADVERTISE_PAUSE_ASYM;
>>>
>>> This bit you probably want to keep. The PHY never says it support
>>> Pause. The MAC needs to enable pause if the MAC supports pause.
>>>
>> Actually I assumed that phylib would do this for me. But:
>> In phy_probe() first phydev->supported is copied to
>> phydev->advertising, and only after this both pause flags are added
>> to phydev->supported. Therefore I think they are not advertised.
>> Is this intentional? It sounds a little weird to me to add the
>> pause flags to the supported features per default, but not
>> advertise them.
> 
> phylib has no idea if the MAC supports Pause. So it should not enable
> it by default. The MAC needs to enable it. And a lot of MAC drivers
> get this wrong...
> 
>> Except e.g. we call by chance phy_set_max_speed(), which copies
>> phydev->supported to phydev->advertising after having adjusted
>> the supported speeds.
> 
> As you correctly pointed out, phy_set_max_speed() is masking out too
> much.
> 
>> If this is not a bug, then where would be the right place to add
>> the pause flags to phydev->advertising?
> 
> Before you call phy_start().
> 
Thanks for the clarification. I think beginning of next week I can
provide a v2 of the patch series.

Heiner


>        Andrew
>