Re: [PATCH net-next v8 6/9] net: phy: c22: migrate to genphy_c45_write_eee_adv()

[Oleksij Rempel]

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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