On Wed, Dec 15, 2021 at 12:34:32AM +0100, Marek Behún wrote: > Common PHYs often have the possibility to specify peak-to-peak voltage > on the differential pair - the default voltage sometimes needs to be > changed for a particular board. I can envision needing this, but I can't say that I've seen custom properties being proposed for this purpose. > > Add properties `tx-amplitude-microvolt` and > `tx-amplitude-microvolt-names` for this purpose. The second property is > needed to specify Is the amplitude peak to peak? You just said it was, but perhaps make the property name more clearly defined: tx-p2p-microvolt > > Example usage with only one voltage (it will be used for all supported > PHY modes, the `tx-amplitude-microvolt-names` property is not needed in > this case): > > tx-amplitude-microvolt = <915000>; > > Example usage with voltages for multiple modes: > > tx-amplitude-microvolt = <915000>, <1100000>, <1200000>; > tx-amplitude-microvolt-names = "2500base-x", "usb", "pcie"; I'm not wild about the -names, but I think outside of ethernet most cases will only be 1 entry. For a phy provider with multiple phys, what if each one needs a different voltage (for the same mode)? > > Signed-off-by: Marek Behún <kabel@xxxxxxxxxx> > --- > > I wanted to constrain the values allowed in the > `tx-amplitude-microvolt-names` property to: > - ethernet SerDes modes (sgmii, qsgmii, 10gbase-r, 2500base-x, ...) > - PCIe modes (pattern: ^pcie[1-6]?$) > - USB modes (pattern: ^usb((-host|-device|-otg)?-(ls|fs|hs|ss|ss\+|4))?$) > - DisplayPort modes (pattern: ^dp(-rbr|-hbr[23]?|-uhbr-(10|13.5|20))?$) > - Camera modes (mipi-dphy, mipi-dphy-univ, mipi-dphy-v2.5-univ) > - Storage modes (sata, ufs-hs, ufs-hs-a, ufs-hs-b) > > But was unable to. The '-names' suffix implies string-array type, and > string-array type does not allow to specify a type for all items in a > simple way, i.e.: > items: > enum: > - sgmii > - sata > - usb > ... Works here: Documentation/devicetree/bindings/arm/samsung/pmu.yaml:56 The requirement is you need to constrain the size with maxItems. It can be a 'should be enough for anyone' value. > Such constraint does work when changing ethernet controller's > `phy-connection-type` to array, see > https://lore.kernel.org/netdev/20211123164027.15618-2-kabel@xxxxxxxxxx/ > > But it seems that string-array type prohibits this. > > --- > .../devicetree/bindings/phy/phy.yaml | 22 +++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/Documentation/devicetree/bindings/phy/phy.yaml b/Documentation/devicetree/bindings/phy/phy.yaml > index a5b6b04cff5b..8915065cf6c2 100644 > --- a/Documentation/devicetree/bindings/phy/phy.yaml > +++ b/Documentation/devicetree/bindings/phy/phy.yaml > @@ -31,9 +31,29 @@ properties: > Phandle to a regulator that provides power to the PHY. This regulator > will be managed during the PHY power on/off sequence. > > + tx-amplitude-microvolt: > + description: > + Transmit amplitude voltages in microvolts, peak-to-peak. If this property > + contains multiple values for various PHY modes, the > + 'tx-amplitude-microvolt-names' property must be provided and contain > + corresponding mode names. > + > + tx-amplitude-microvolt-names: > + description: | > + Names of the modes corresponding to voltages in the > + 'tx-amplitude-microvolt' property. Required only if multiple voltages > + are provided. > + > + If a value of 'default' is provided, the system should use it for any PHY > + mode that is otherwise not defined here. If 'default' is not provided, the > + system should use manufacturer default value. > + > required: > - '#phy-cells' > > +dependencies: > + tx-amplitude-microvolt-names: [ tx-amplitude-microvolt ] > + > additionalProperties: true > > examples: > @@ -46,6 +66,8 @@ examples: > phy: phy { > #phy-cells = <1>; > phy-supply = <&phy_regulator>; > + tx-amplitude-microvolt = <915000>, <1100000>, <1200000>; > + tx-amplitude-microvolt-names = "2500base-x", "usb-hs", "usb-ss"; > }; > > ethernet-controller { > -- > 2.32.0 > >
