On Mon, 2014-12-22 at 05:08 -0600, Emil Medve wrote: > Hello Scott, > > > On 12/22/2014 03:42 AM, Scott Wood wrote: > > On Mon, 2014-12-22 at 03:37 -0600, Emil Medve wrote: > >> Hello Scott, > >> > >> > >> On 12/22/2014 02:32 AM, Scott Wood wrote: > >>> On Mon, 2014-12-22 at 02:20 -0600, Emil Medve wrote: > >>>> For the purpose of an example in the binding document, I suggest we just > >>>> stick with the IEEE standard frequency. > >>> > >>> The whole reason for this property existing in the device tree is > >>> non-standard frequencies. > >> > >> While the standard claims 2.5 MHz, most MDIO controllers and PHY devices > >> support frequencies well beyond the standard. Specifying a lower then > >> the standard frequency for the benefit of some errata is just one side > >> of this property > > > > The erratum was (until now) the only claimed reason for it. If there > > are other reasons why one would specify a different frequency (in > > particular, that relate to hardware description), please elaborate. > > From memory, the 1 Gb/s Vitesse PHY(s) we have on some of our DS boards > support 12.5 MHz. I can dig out more specs for specifics on other PHY(s) > > 2.5 MHz is slow and even more so for high speed interfaces. With both > polling and interrupts (both MDIO and/or PHY) we've noticed (or blamed) > in the past some Ethernet performance issues on this very slowness > > As of right now I'm not aware of another way to specify/coordinate the > MDC speed so setting a default (common denominator) in the DT that is > different then the IEEE standard seems ok > > >>>> We can continue this conversation about errata handling when we submit > >>>> the code relevant to this binding (and the FMan v3 support) > >>> > >>> It affects the binding, so let's discuss it now please. > >> > >> I think this specific (unpublished yet) errata has less bearing on the > >> binding then you might believe. This is mostly about providing a > >> common/default frequency supported by all the devices on some board > > > > What reason other than an erratum would there be for the standard > > frequency not being supported? > > This is not about not supporting the standard frequency. This is about > the default frequency being different then the standard OK, though rather than talk about defaults I'd phrase it as indicating that a higher frequency than standard is supported, or that a lower frequency than standard is required. -Scott -- 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
