From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from na01-bn1-obe.outbound.protection.outlook.com (mail-bn1bon0116.outbound.protection.outlook.com [157.56.111.116]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id B831F1A0D48 for ; Mon, 22 Dec 2014 22:08:51 +1100 (AEDT) Message-ID: <5497FBAB.4010206@Freescale.com> Date: Mon, 22 Dec 2014 05:08:27 -0600 From: Emil Medve MIME-Version: 1.0 To: Scott Wood Subject: Re: [PATCH] [v2] power/fsl: add MDIO dt binding for FMan References: <1415958800-9867-1-git-send-email-shh.xie@gmail.com> <1416966592.15957.172.camel@freescale.com> <1418940078.5581.143.camel@freescale.com> <1419030955.5581.154.camel@freescale.com> <5497D466.9090804@Freescale.com> <1419237176.5581.159.camel@freescale.com> <5497E645.7010500@Freescale.com> <1419241330.5581.162.camel@freescale.com> In-Reply-To: <1419241330.5581.162.camel@freescale.com> Content-Type: text/plain; charset="utf-8" Cc: "devicetree@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , Xie Shaohui-B21989 , Liberman Igal-B31950 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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,