On Friday 18 October 2013 07:42 PM, Matt Porter wrote: > This is a summary of an unresolved issue resulting from this thread: > http://www.spinics.net/lists/arm-kernel/msg277700.html > > The BCM281xx family of SoCs contain an OTG subsystem consisting of a > DWC2 HSOTG controller and an internal UTMI PHY. This is appears as > follows (monospace font requirement ahead): > > +----------------+ +-----------------+ > | | | | > | | 8 | | > | DWC2 |<------/----->| BCM Kona | > | | UTMI | UTMI PHY | > | | | | > +----------------+ +-----------------+ > > The internal UTMI phy is connected via an 8-bit data path. There is > no way to autodetect whether the data path is 8-bit or 16-bit. As such, > it was determined that a DT property is necessary to reflect this. > > In the original patch submitted this property was offered as an > additional optional dwc2 property: > > --- a/Documentation/devicetree/bindings/staging/dwc2.txt > +++ b/Documentation/devicetree/bindings/staging/dwc2.txt > @@ -6,10 +6,14 @@ Required properties: > - reg : Should contain 1 register range (address and length) > - interrupts : Should contain 1 interrupt > > +Optional properties: > +- snps,phy-utmi-width: Must contain the UTMI data width (either 8 or 16) > + > Example: > > usb@101c0000 { > compatible = "ralink,rt3050-usb, snps,dwc2"; > reg = <0x101c0000 40000>; > interrupts = <18>; > + snps,phy-utmi-width = <8>; > }; > > The open question is whether this required hardware property belongs to > the DWC2 controller or the PHY itself. I think it makes sense to keep the data width property in the dwc2 node itself. I mean it describes how the dwc2 IP is configured in that particular SoC (given that it can be either <8> or <16>). Thanks Kishon > > If the UTMI data path width is considered to be a property of the PHY > then this will impact both the generic PHY framework and the PHY device > node (producer) binding. The binding would need to be extended to carry > the data path width property. In addition, the generic PHY framework > would need to allow for this information to be gathered in some manner > for use by the controller driver (PHY consumer). In the case of DWC2, > the driver needs to know whether to program the phy interface for 8 or > 16 bit UTMI communication. > > Thanks, > Matt > -- > To unsubscribe from this list: send the line "unsubscribe linux-usb" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
