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 I think this specific (unpublished yet) errata has less bearing on the 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 Cheers, -- 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
