Messages in this thread | | | Date | Wed, 15 Dec 2021 00:49:14 +0000 | From | "Russell King (Oracle)" <> | Subject | Re: [PATCH] net: phylink: Pass state to pcs_config |
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On Tue, Dec 14, 2021 at 07:16:53PM -0500, Sean Anderson wrote: > Ok, so let me clarify my understanding. Perhaps this can be eliminated > through a different approach. > > When I read the datasheet for mvneta (which hopefully has the same > logic here, since I could not find a datasheet for an mvpp2 device), I > noticed that the Pause_Adv bit said > > > It is valid only if flow control mode is defined by Auto-Negotiation > > (as defined by the <AnFcEn> bit). > > Which I interpreted to mean that if AnFcEn was clear, then no flow > control was advertised. But perhaps it instead means that the logic is > something like > > if (AnFcEn) > Config_Reg.PAUSE = Pause_Adv; > else > Config_Reg.PAUSE = SetFcEn; > > which would mean that we can just clear AnFcEn in link_up if the > autonegotiated pause settings are different from the configured pause > settings.
Having actually played with this hardware quite a bit and observed what it sends, what it implements for advertising is:
Config_Reg.PAUSE = Pause_Adv;
Config_Reg gets sent over the 1000BASE-X link to the link partner, and we receive Remote_Reg from the link partner.
Then, the hardware implements:
if (AnFcEn) MAC_PAUSE = Config_Reg.PAUSE & Remote_Reg.PAUSE; else MAC_PAUSE = SetFcEn;
In otherwords, AnFcEn controls whether the result of autonegotiation or the value of SetFcEn controls whether the MAC enables symmetric pause mode.
Pause_Adv comes from the advertisement, and this is controlled from ethtool -s and somewhat by ethtool -A.
AnFcEn is controlled purely and only by ethtool -A ... autoneg on|off. You can't derive this from "state".
SetFcEn comes from ethtool -A ... tx and rx parameters (which must both be on or both be off.)
Since we have no knowledge what Remote_Reg contains (it's not made accessible by the hardware), it's impossible to derive whether the autonegotiated pause settings are different from the configured pause settings.
-- 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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