On Tue, Mar 05, 2024 at 12:20:39PM +0800, Choong Yong Liang wrote: > > > On 23/2/2024 2:58 pm, Voon, Weifeng wrote: > > > > For instance, if the interface switches from 2500baseX to SGMII mode, > > > > and the current link mode is MLO_AN_PHY, calling > > > 'phylink_pcs_neg_mode' > > > > would yield PHYLINK_PCS_NEG_OUTBAND. Since the MAC and PCS driver > > > > require PHYLINK_PCS_NEG_INBAND_ENABLED, the > > > 'mac_get_pcs_neg_mode' > > > > function will calculate the mode based on the interface, current link > > > > negotiation mode, and advertising link mode, returning > > > > PHYLINK_PCS_NEG_OUTBAND to enable the PCS to configure the correct > > > settings. > > > > > > This paragraph doesn't make sense - at least to me. It first talks about > > > requiring PHYLINK_PCS_NEG_INBAND_ENABLED when in SGMII mode. On > > > this: > > > > The example given here is a very specific condition and that probably why there are some confusions here. Basically, this patch provides an optional function for MAC driver to change the phy interface on-the-fly without the need of reinitialize the Ethernet driver. As we know that the 2500base-x is messy, in our case the 2500base-x does not support inband. To complete the picture, we are using SGMII c37 to handle speed 10/100/1000. Hence, to enable user to switch link speed from 2500 to 1000/100/10 and vice versa on-the-fly, the phy interface need to be configured to inband SGMII for speed 10/100/1000, and outband 2500base-x for speed 2500. Lastly, the newly introduced "mac_get_pcs_neg_mode"callback function enables MAC driver to reconfigure pcs negotiation mode to inband or outband based on the interface mode, current link negotiation mode, and advertising link mode. > > > > > > > > 1) are you sure that the hardware can't be programmed for the SGMII > > > symbol repititions? > > > > > > > No, the HW can be program for SGMII symbol repetitions. > > > > > 2) what happens if you're paired with a PHY (e.g. on a SFP module) which > > > uses SGMII but has no capability of providing the inband data? > > > (They do exist.) If your hardware truly does require inband data, it is going to > > > be fundamentally inoperative with these modules. > > > > > > > Above explanation should have already cleared your doubts. Inband or outband capability is configured based on the phy interface. > > > > > Next, you then talk about returning PHYLINK_PCS_NEG_OUTBAND for the > > > "correct settings". How does this relate to the first part where you basically > > > describe the problem as SGMII requring inband? Basically the two don't > > > follow. > > > > It should be a typo mistake. SGMII should return PHYLINK_PCS_NEG_INBAND_ENABLED. > > > > > > > > How, from a design point of view, because this fundamentally allows drivers > > > to change how the system behaves, it will allow radically different behaviours > > > for the same parameters between different drivers. > > > I am opposed to that - I want to see a situation where we have uniform > > > behaviour for the same configuration, and where hardware doesn't support > > > something, we have some way to indicate that via some form of capabilities. > > > > > > > Hi Russell, > > If I understand you correctly, MAC driver should not interfere with pcs negotiation mode and it should be standardized in the generic function, e.g., phylink_pcs_neg_mode()? > > > > > The issue of whether 2500base-X has inband or not is a long standing issue, > > > and there are arguments (and hardware) that take totally opposing views on > > > this. There is hardware where 2500base-X inband _must_ be used or the link > > > doesn't come up. There is also hardware where 2500base-X inband is not > > > "supported" in documentation but works in practice. There is also hardware > > > where 2500base-X inband doesn't work. The whole thing is a total mess > > > (thanks IEEE 802.3 for not getting on top of this early enough... and what's > > > now stated in 802.3 for 2500base-X is now irrelevant because they were too > > > late to the > > > party.) > > > > > > > Agreed. And I have also seen some of your comments regarding the 2500SGMII and 2500BASEX. > > > Hi Russell, > > Did the previous reply clear your doubt? I am working on the problem as and when I can find the time (which is not much spare time.) I have some prototype code at the moment. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
