On 3/24/2021 4:00 PM, Marek Behún wrote: > On Wed, 24 Mar 2021 14:19:28 -0700 > Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: > >>> Another problem is that if lower modes are supported, we should >>> maybe use them in order to save power. >> >> That is an interesting proposal but if you want it to be truly valuable, >> does not that mean that an user ought to be able to switch between any >> of the supported PHY <=> MAC interfaces at runtime, and then within >> those interfaces to the speeds that yield the best power savings? > > If the code determines that there are multiple working configurations, > it theoretically could allow the user to switch between them. > > My idea was that this should be done by kernel, though. > > But power saving is not the main problem I am trying to solve. > What I am trying to solve is that if a board does not support all modes > supported by the MAC and PHY, because they are not wired or something, > we need to know about that so that we can select the correct mode for > PHYs that change this mode at runtime. OK so the runtime part comes from plugging in various SFP modules into a cage but other than that, for a "fixed" link such as a SFF or a soldered down PHY, do we agree that there would be no runtime changing of the 'phy-mode'? What I am trying to understand is why this needs to be added to the Device Tree as opposed to a bitmask within the PHY driver that indicates the various interface mode capabilities which, looking at the code you shared below, is how you make decisions ultimately. > >>> >>> But for this we need to know which phy-modes are supported on the >>> board. >>> >>> This series adds documentation for a new ethernet PHY property, >>> called `supported-mac-connection-types`. >> >> That naming does not quite make sense to me, if we want to describe the >> MAC supported connection types, then those would naturally be within the >> Ethernet MAC Device Tree node, no? If we are describing what the PHY is >> capable, then we should be dropping "mac" from the property name not to >> create confusion. > > I put "mac" there to indicate that this is the SerDes to the MAC (i.e. > host side in Marvell PHY). 88X3310 has another SerDes side (Fiber Side). > I guess I put "mac" there so that if in the future we wanted to specify > supported modes for the fiber side, we could add > `supported-fiber-connection-types`. You would traditionally find the words "line side" (copper, optical, etc.) and "MAC side" being used in datasheets, maybe you can use a similar naming here? > > But otherwise it does not matter where this property is. Rob Herring > says that maybe we don't need a new property at all. We can reuse > phy-mode property of the MAC, and enumerate all supported modes there. > >> >>> >>> When this property is present for a PHY node, only the phy-modes >>> listed in this property should be considered to be functional on >>> the board. >> >> Can you post the code that is going to utilize these properties so we >> have a clearer picture of how and what you need to solve? > > I am still working on this, so the repo may change, but look at > https://git.kernel.org/pub/scm/linux/kernel/git/kabel/linux.git/log/?h=phy-supported-interfaces > at the last three patches. > -- Florian
