netdev - Re: [PATCH net-next] r8169: copy vendor driver 2.5G/5G EEE advertisement constraints

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Message-ID: <5f5a45ff-dff8-4a04-9028-88b189862fcb@lunn.ch>
Date: Wed, 6 Nov 2024 16:22:05 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Heiner Kallweit <hkallweit1@...il.com>
Cc: Realtek linux nic maintainers <nic_swsd@...ltek.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Paolo Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] r8169: copy vendor driver 2.5G/5G EEE
 advertisement constraints

On Wed, Nov 06, 2024 at 02:28:54PM +0100, Heiner Kallweit wrote:
> On 05.11.2024 22:06, Andrew Lunn wrote:
> > On Mon, Nov 04, 2024 at 11:07:20PM +0100, Heiner Kallweit wrote:
> >> Vendor driver r8125 doesn't advertise 2.5G EEE on RTL8125A, and r8126
> >> doesn't advertise 5G EEE. Likely there are compatibility issues,
> >> therefore do the same in r8169.
> >> With this change we don't have to disable 2.5G EEE advertisement in
> >> rtl8125a_config_eee_phy() any longer.
> >> Note: We don't remove the potentially problematic modes from the
> >> supported modes, so users can re-enable advertisement of these modes
> >> if they work fine in their setup.
> >>
> >> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> >> ---
> >>  drivers/net/ethernet/realtek/r8169_main.c       |  7 +++++++
> >>  drivers/net/ethernet/realtek/r8169_phy_config.c | 16 ++++------------
> >>  2 files changed, 11 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> >> index e83c4841b..4f37d25e0 100644
> >> --- a/drivers/net/ethernet/realtek/r8169_main.c
> >> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> >> @@ -5318,6 +5318,13 @@ static int r8169_mdio_register(struct rtl8169_private *tp)
> >>  		phy_support_eee(tp->phydev);
> >>  	phy_support_asym_pause(tp->phydev);
> >>  
> >> +	/* mimic behavior of r8125/r8126 vendor drivers */
> >> +	if (tp->mac_version == RTL_GIGA_MAC_VER_61)
> >> +		linkmode_clear_bit(ETHTOOL_LINK_MODE_2500baseT_Full_BIT,
> >> +				   tp->phydev->advertising_eee);
> >> +	linkmode_clear_bit(ETHTOOL_LINK_MODE_5000baseT_Full_BIT,
> >> +			   tp->phydev->advertising_eee);
> > 
> > Hi Heiner
> > 
> > phy_device.c has:
> > 
> > /**
> >  * phy_remove_link_mode - Remove a supported link mode
> >  * @phydev: phy_device structure to remove link mode from
> >  * @link_mode: Link mode to be removed
> >  *
> >  * Description: Some MACs don't support all link modes which the PHY
> >  * does.  e.g. a 1G MAC often does not support 1000Half. Add a helper
> >  * to remove a link mode.
> >  */
> > void phy_remove_link_mode(struct phy_device *phydev, u32 link_mode)
> > {
> >         linkmode_clear_bit(link_mode, phydev->supported);
> >         phy_advertise_supported(phydev);
> > }
> > EXPORT_SYMBOL(phy_remove_link_mode);
> > 
> > Maybe we need a phy_remove_eee_link_mode()? That could also remove it
> > from supported? At minimum, it would stop MAC drivers poking around
> > the insides of phylib.
> > 
> After checking eee_broken_modes in more detail:
> In general it does what I need, it prevents broken EEE modes from being
> advertised. Some challenges:
> 
> - eee_broken_modes currently represents eee_cap1 register bits.
>   So it's not possible to flag 2.5G or 5G EEE as broken.
>   - We would have to change eee_broken_modes to a linkmode bitmap.
> 
> - eee_broken_modes can be populated via DT only.
>   of_set_phy_eee_broken() would have to be changed to operate on
>   fwnodes. Then I may be able to "inject" the broken modes in my
>   case as swnode's.
>   Not the easiest solution, but maybe the cleanest. Feedback welcome.

I probably would not go as far as adding swnode support for something
so simple. Just add phy_remove_eee_link_mode() or maybe
phy_set_eee_broken() as i suggested to set bits in
phydev->eee_broken_modes.

And converting it to a linkmode bitmap is probably needed in the long
term anyway. the change does not look too invasive, eee_broken_mode is
not used in many places.

I say go for it.

	Andrew