On Thu, Nov 23, 2023 at 06:57:59PM +0800, Jie Luo wrote: > On 11/21/2023 7:52 PM, Russell King (Oracle) wrote: > > Ultimately, you will need a way to use inband signalling with Cisco > > SGMII for 10M/100M/1G speeds, and then switch to 2500base-X when > > operating at 2.5G speeds, and that is done via the PHY driver > > updating phydev->interface. > > > > What we do need is some way for the PHY to also tell the PCS/MAC > > whether inband should be used. This is something I keep bringing up > > and now that we have PCS drivers revised to use the value from > > phylink_pcs_neg_mode() _and_ a consistent implementation amongst them > > we can now think about signalling to PCS drivers whether inband mode > > needs to be turned off when switching between modes. > > Yes, we can switch the interface mode according to the current link > speed in the pcs driver. > but the issue is that the phy-mode i specified for the PHYLINK, > if phy-mode is sgmii, the support capability is limited to maximum > capability 1G during the PHYLINK setup and i can't configure it to 2.5G > dynamically, if the phy-mode is 2500base-x, then PHY capability will > be modified to only support 2.5G, other speeds can't be linked up. So you need my patches that add "possible_interfaces" to phylib so you can tell phylink that you will be switching between SGMII and 2500base-X. Please see the RFC posting of those patches I sent yesterday and try them out - you will need to modify your phylib driver to fill in phydev->possible_interfaces. > > There have been patches in the past that allow inband mode to be > > queried from phylib, and this is another important component in > > properly dealing with PHYs that need to use inband signalling with > > Cisco SGMII, but do not support inband signalling when operating at > > 2.5G speeds. The problem when operating at 2.5G speed is that the > > base-X protocols are normally for use over fibre, which is the media, > > and therefore the ethtool Autoneg bit should define whether inband > > gets used or not. However, in the case of a PHY using 2500base-X, > > the Autoneg bit continues to define whether autonegotiation should > > be used on the media, and in this case it's the media side of the > > PHY rather than the 2500base-X link. > > > > So, when using a 2500base-X link to a PHY, we need to disregard the > > Autoneg bit, but that then raises the question about how we should > > configure it - and one solution to that would be to entire of phylib > > what the PHY wants to do. Another is to somehow ask the PCS driver > > whether it supports inband signalling at 2500base-X, and resolve > > those capabilities. > > For the qca808x PHY, when it is linked in 2.5G, the autoneg is also > disabled in PCS hardware, so the sgmii+ of qca808x PHY is almost > same as 2500base-X. Not "almost". It _is_ the same. This is the point I've been trying to get across to you. Without inband signalling, 1000base-X and SGMII (when operating at 1G) are _identical_ and entirely compatible. You've said that your 2.5G "SGMII" mode has inband signalling disabled, and thus it without inband signalling, 2500base-X and this 2.5G mode are again identical and entirely compatible. There's no "almost" about it. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
