On Tue, 2025-04-15 at 16:06 +0530, Siddharth Vadapalli wrote: > > On Tue, Apr 15, 2025 at 12:18:01PM +0200, Matthias Schiffer wrote: > > As discussed [1], the comments for the different rgmii(-*id) modes do not > > accurately describe what these values mean. > > > > As the Device Tree is primarily supposed to describe the hardware and not > > its configuration, the different modes need to distinguish board designs > > If the Ethernet-Controller (MAC) is integrated in an SoC (as is the case > with CPSW Ethernet Switch), and, given that "phy-mode" is a property > added within the device-tree node of the MAC, I fail to understand how > the device-tree can continue "describing" hardware for different board > designs using the same SoC (unchanged MAC HW). The setting is part of the MAC node, but it is always set in the board DTS, together with assigning a PHY to the MAC. > How do we handle situations where a given MAC supports various > "phy-modes" in HW? Shouldn't "phy-modes" then be a "list" to technically > descibe the HW? Even if we set aside the "rgmii" variants that this > series is attempting to address, the CPSW MAC supports "sgmii", "qsgmii" > and "usxgmii/xfi" as well. This is not about PHY mode support of the MAC, but the mode to be used on a particular board. I would not expect a board to use multiple different interfaces with a single PHY (and if such cases exist, I consider them out of scope for this patch series). > > > (if a delay is built into the PCB using different trace lengths); whether > > a delay is added on the MAC or the PHY side when needed should not matter. > > > > Unfortunately, implementation in MAC drivers is somewhat inconsistent > > where a delay is fixed or configurable on the MAC side. As a first step > > towards sorting this out, improve the documentation. > > > > Link: https://lore.kernel.org/lkml/d25b1447-c28b-4998-b238-92672434dc28@xxxxxxx/ [1] > > Signed-off-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx> > > --- > > .../bindings/net/ethernet-controller.yaml | 16 +++++++++------- > > 1 file changed, 9 insertions(+), 7 deletions(-) > > > > diff --git a/Documentation/devicetree/bindings/net/ethernet-controller.yaml b/Documentation/devicetree/bindings/net/ethernet-controller.yaml > > index 45819b2358002..2ddc1ce2439a6 100644 > > --- a/Documentation/devicetree/bindings/net/ethernet-controller.yaml > > +++ b/Documentation/devicetree/bindings/net/ethernet-controller.yaml > > @@ -74,19 +74,21 @@ properties: > > - rev-rmii > > - moca > > > > - # RX and TX delays are added by the MAC when required > > + # RX and TX delays are part of the board design (through PCB traces). MAC > > + # and PHY must not add delays. > > - rgmii > > > > - # RGMII with internal RX and TX delays provided by the PHY, > > - # the MAC should not add the RX or TX delays in this case > > + # RGMII with internal RX and TX delays provided by the MAC or PHY. No > > + # delays are included in the board design; this is the most common case > > + # in modern designs. > > - rgmii-id > > > > - # RGMII with internal RX delay provided by the PHY, the MAC > > - # should not add an RX delay in this case > > + # RGMII with internal RX delay provided by the MAC or PHY. TX delay is > > + # part of the board design. > > - rgmii-rxid > > > > - # RGMII with internal TX delay provided by the PHY, the MAC > > - # should not add an TX delay in this case > > + # RGMII with internal TX delay provided by the MAC or PHY. RX delay is > > + # part of the board design. > > Since all of the above is documented in "ethernet-controller.yaml" and > not "ethernet-phy.yaml", describing what the "MAC" should or shouldn't > do seems accurate, and modifying it to describe what the "PHY" should or > shouldn't do seems wrong. The settings describe the connection between MAC and PHY, thus their explanation must mention both to make sense. See the linked discussion with Andrew for details. Best, Matthias > > > - rgmii-txid > > - rtbi > > - smii > > Regards, > Siddharth. -- TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany Amtsgericht München, HRB 105018 Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider https://www.tq-group.com/
