netdev - Re: [PATCH net-next v8 6/9] net: phy: c22: migrate to genphy_c45_write_eee

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Message-ID: <20230225060812.GB8437@pengutronix.de>
Date:   Sat, 25 Feb 2023 07:08:12 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Woojung Huh <woojung.huh@...rochip.com>,
        Andrew Lunn <andrew@...n.ch>, Arun.Ramadoss@...rochip.com,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, UNGLinuxDriver@...rochip.com,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, Wei Fang <wei.fang@....com>,
        kernel@...gutronix.de, intel-wired-lan@...ts.osuosl.org,
        Jakub Kicinski <kuba@...nel.org>,
        Vladimir Oltean <olteanv@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH net-next v8 6/9] net: phy: c22: migrate to
 genphy_c45_write_eee_adv()

On Fri, Feb 24, 2023 at 04:09:40PM -0800, Guenter Roeck wrote:
> On 2/24/23 12:02, Oleksij Rempel wrote:
> [ ... ]
> > > 
> > > For cubieboard:
> > > 
> > > MDIO_PCS_EEE_ABLE = 0x0000
> > > 
> > > qemu reports attempts to access unsupported registers.
> > > 
> > > I had a look at the Allwinner mdio driver. There is no indication suggesting
> > > what the real hardware would return when trying to access unsupported registers,
> > > and the Ethernet controller datasheet is not public.
> > 
> > These are PHY accesses over MDIO bus. Ethernet controller should not
> > care about content of this operations. But on qemu side, it is implemented as
> > part of Ethernet controller emulation...
> > 
> > Since MDIO_PCS_EEE_ABLE == 0x0000, phydev->supported_eee should prevent
> > other EEE related operations. But may be actual phy_read_mmd() went
> > wrong. It is a combination of simple phy_read/write to different
> > registers.
> > 
> 
> Adding MDD read/write support in qemu doesn't help. Something else in your patch
> prevents the PHY from coming up. After reverting your patch, I see
> 
> sun4i-emac 1c0b000.ethernet eth0: Link is Up - 100Mbps/Full - flow control off
> IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
> 
> in the log. This is missing with your patch in place.
> 
> Anyway, the key difference is not really the qemu emulation, but the added
> unconditional call to genphy_c45_write_eee_adv() in your patch. If you look
> closely into that function, you may notice that the 'changed' variable is
> never set to 0.
> 
> diff --git a/drivers/net/phy/phy-c45.c b/drivers/net/phy/phy-c45.c
> index 3813b86689d0..fee514b96ab1 100644
> --- a/drivers/net/phy/phy-c45.c
> +++ b/drivers/net/phy/phy-c45.c
> @@ -672,7 +672,7 @@ EXPORT_SYMBOL_GPL(genphy_c45_read_mdix);
>   */
>  int genphy_c45_write_eee_adv(struct phy_device *phydev, unsigned long *adv)
>  {
> -       int val, changed;
> +       int val, changed = 0;
> 
>         if (linkmode_intersects(phydev->supported_eee, PHY_EEE_CAP1_FEATURES)) {
>                 val = linkmode_to_mii_eee_cap1_t(adv);
> 
> fixes the problem, both for cubieboard and xtensa.

Good point! Thx for finding it!

Do you wont to send the fix against net?
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