Messages in this thread | | | Date | Wed, 29 Mar 2023 10:48:09 +0100 | From | "Russell King (Oracle)" <> | Subject | Re: [PATCH net v3 1/3] net: phylink: add phylink_expects_phy() method |
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On Wed, Mar 29, 2023 at 09:34:05AM +0000, Sit, Michael Wei Hong wrote: > > > > -----Original Message----- > > From: Russell King <linux@armlinux.org.uk> > > Sent: Wednesday, March 29, 2023 5:01 PM > > To: Jakub Kicinski <kuba@kernel.org> > > Cc: Sit, Michael Wei Hong <michael.wei.hong.sit@intel.com>; > > Giuseppe Cavallaro <peppe.cavallaro@st.com>; Alexandre Torgue > > <alexandre.torgue@foss.st.com>; Jose Abreu > > <joabreu@synopsys.com>; David S . Miller <davem@davemloft.net>; > > Eric Dumazet <edumazet@google.com>; Paolo Abeni > > <pabeni@redhat.com>; Maxime Coquelin > > <mcoquelin.stm32@gmail.com>; Ong, Boon Leong > > <boon.leong.ong@intel.com>; netdev@vger.kernel.org; linux- > > stm32@st-md-mailman.stormreply.com; linux-arm- > > kernel@lists.infradead.org; linux-kernel@vger.kernel.org; Looi, > > Hong Aun <hong.aun.looi@intel.com>; Voon, Weifeng > > <weifeng.voon@intel.com>; Lai, Peter Jun Ann > > <peter.jun.ann.lai@intel.com> > > Subject: Re: [PATCH net v3 1/3] net: phylink: add > > phylink_expects_phy() method > > > > On Tue, Mar 28, 2023 at 06:57:20PM -0700, Jakub Kicinski wrote: > > > On Fri, 24 Mar 2023 16:16:54 +0800 Michael Sit Wei Hong wrote: > > > > Provide phylink_expects_phy() to allow MAC drivers to check if it > > is > > > > expecting a PHY to attach to. Since fixed-linked setups do not > > need > > > > to attach to a PHY. > > > > > > > > Provides a boolean value as to if the MAC should expect a PHY. > > > > returns true if a PHY is expected. > > > > > > > > Signed-off-by: Michael Sit Wei Hong > > <michael.wei.hong.sit@intel.com> > > > > > > Russell, looks good? > > > > Not really, given that phylink_attach_phy() will refuse to attach a > > PHY > > when: > > > > if (WARN_ON(pl->cfg_link_an_mode == MLO_AN_FIXED || > > (pl->cfg_link_an_mode == MLO_AN_INBAND && > > phy_interface_mode_is_8023z(interface) && !pl- > > >sfp_bus))) > > return -EINVAL; > > > > So, if we introduce a helper named "phylink_expects_phy" that > > returns true when cfg_link_an_mode == MLO_AN_INBAND and the > > interface mode is e.g. 1000base-X, but then someone tries to attach > > a PHY, the kernel spits out a warning, backtrace, and a return value > > of -EINVAL, things are going to look really rather stupid. > > > Should we check for these 3 conditions as well then? > (pl->cfg_link_an_mode == MLO_AN_INBAND && > phy_interface_mode_is_8023z(interface) && !pl->sfp_bus) > to determine if phylink expects a phy.
If there's a sfp bus, then we don't expect a PHY from the MAC driver (as there can only be one PHY attached), and as phylink_expects_phy() is for the MAC driver to use, we should be returning false if pl->sfp_bus != NULL.
pl->cfg_link_an_mode == MLO_AN_FIXED || (pl->cfg_link_an_mode == MLO_AN_INBAND && phy_interface_mode_is_8023z(interface))
Is true when we're in fixed-link mode, or if we're in in-band mode and using 1000base-X or 25000base-X. These are the conditions that we don't expect the MAC driver to give us a PHY.
To put that in positive logic, we expect a PHY from the MAC when we're in PHY mode, or when we're in in-band mode and using SGMII, QSGMII, USXGMII, RGMII, etc.
The reason for the extra "&& !pl->sfp_bus" in phylink_attach_phy() is to allow SFPs to connect to the MAC using inband mode with 1000base-X and 2500base-X interface modes. These are not for the MAC-side of things though.
-- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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