Messages in this thread | | | Subject | Re: [PATCH] net: phy: fix auto-negotiation in case of 'down-shift' | From | Heiner Kallweit <> | Date | Tue, 24 Nov 2020 16:03:40 +0100 |
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Am 24.11.2020 um 15:38 schrieb Antonio Borneo: > If the auto-negotiation fails to establish a gigabit link, the phy > can try to 'down-shift': it resets the bits in MII_CTRL1000 to > stop advertising 1Gbps and retries the negotiation at 100Mbps. > I see that Russell answered already. My 2cts:
Are you sure all PHY's supporting downshift adjust the advertisement bits? IIRC an Aquantia PHY I dealt with does not. And if a PHY does so I'd consider this problematic: Let's say you have a broken cable and the PHY downshifts to 100Mbps. If you change the cable then the PHY would still negotiate 100Mbps only.
Also I think phydev->advertising reflects what the user wants to advertise, as mentioned by Russell before.
>>From commit 5502b218e001 ("net: phy: use phy_resolve_aneg_linkmode > in genphy_read_status") the content of MII_CTRL1000 is not checked > anymore at the end of the negotiation, preventing the detection of > phy 'down-shift'. > In case of 'down-shift' phydev->advertising gets out-of-sync wrt > MII_CTRL1000 and still includes modes that the phy have already > dropped. The link partner could still advertise higher speeds, > while the link is established at one of the common lower speeds. > The logic 'and' in phy_resolve_aneg_linkmode() between > phydev->advertising and phydev->lp_advertising will report an > incorrect mode. > > Issue detected with a local phy rtl8211f connected with a gigabit > capable router through a two-pairs network cable. > > After auto-negotiation, read back MII_CTRL1000 and mask-out from > phydev->advertising the modes that have been eventually discarded > due to the 'down-shift'. > > Fixes: 5502b218e001 ("net: phy: use phy_resolve_aneg_linkmode in genphy_read_status") > Cc: stable@vger.kernel.org # v5.1+ > Signed-off-by: Antonio Borneo <antonio.borneo@st.com> > Link: https://lore.kernel.org/r/478f871a-583d-01f1-9cc5-2eea56d8c2a7@huawei.com > --- > To: Andrew Lunn <andrew@lunn.ch> > To: Heiner Kallweit <hkallweit1@gmail.com> > To: Russell King <linux@armlinux.org.uk> > To: "David S. Miller" <davem@davemloft.net> > To: Jakub Kicinski <kuba@kernel.org> > To: netdev@vger.kernel.org > To: Yonglong Liu <liuyonglong@huawei.com> > Cc: linuxarm@huawei.com > Cc: Salil Mehta <salil.mehta@huawei.com> > Cc: linux-stm32@st-md-mailman.stormreply.com > Cc: linux-kernel@vger.kernel.org > Cc: Antonio Borneo <antonio.borneo@st.com> > > drivers/net/phy/phy_device.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c > index 5dab6be6fc38..5d1060aa1b25 100644 > --- a/drivers/net/phy/phy_device.c > +++ b/drivers/net/phy/phy_device.c > @@ -2331,7 +2331,7 @@ EXPORT_SYMBOL(genphy_read_status_fixed); > */ > int genphy_read_status(struct phy_device *phydev) > { > - int err, old_link = phydev->link; > + int adv, err, old_link = phydev->link; > > /* Update the link, but return if there was an error */ > err = genphy_update_link(phydev); > @@ -2356,6 +2356,14 @@ int genphy_read_status(struct phy_device *phydev) > return err; > > if (phydev->autoneg == AUTONEG_ENABLE && phydev->autoneg_complete) { > + if (phydev->is_gigabit_capable) { > + adv = phy_read(phydev, MII_CTRL1000); > + if (adv < 0) > + return adv; > + /* update advertising in case of 'down-shift' */ > + mii_ctrl1000_mod_linkmode_adv_t(phydev->advertising, > + adv); > + } > phy_resolve_aneg_linkmode(phydev); > } else if (phydev->autoneg == AUTONEG_DISABLE) { > err = genphy_read_status_fixed(phydev); > > base-commit: d549699048b4b5c22dd710455bcdb76966e55aa3 >
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