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From: Emil Medve <Emilian.Medve-eDlz3WWmN0ll57MIdRCFDg@public.gmane.org>
To: Scott Wood <scottwood-eDlz3WWmN0ll57MIdRCFDg@public.gmane.org>
Cc: Xie Shaohui-B21989
	<Shaohui.Xie-eDlz3WWmN0ll57MIdRCFDg@public.gmane.org>,
	"linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org"
	<linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org>,
	"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Liberman Igal-B31950
	<Igal.Liberman-eDlz3WWmN0ll57MIdRCFDg@public.gmane.org>
Subject: Re: [PATCH] [v2] power/fsl: add MDIO dt binding for FMan
Date: Mon, 22 Dec 2014 05:08:27 -0600	[thread overview]
Message-ID: <5497FBAB.4010206@Freescale.com> (raw)
In-Reply-To: <1419241330.5581.162.camel-KZfg59tc24xl57MIdRCFDg@public.gmane.org>

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,
--
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  parent reply	other threads:[~2014-12-22 11:08 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-14  9:53 [PATCH] [v2] power/fsl: add MDIO dt binding for FMan shh.xie-Re5JQEeQqe8AvxtiuMwx3w
     [not found] ` <1415958800-9867-1-git-send-email-shh.xie-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-11-20 13:00   ` Shaohui Xie
2014-11-26  1:49   ` Scott Wood
     [not found]     ` <1416966592.15957.172.camel-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
2014-11-26  2:10       ` Shaohui Xie
2014-12-18 12:53     ` Shaohui Xie
     [not found]       ` <DM2PR0301MB08641FB289DBA17AD59FBEA0E26A0-Cwg/PA1lyPnq20u2fDgSrZwN6zqB+hSMnBOFsp37pqbUKgpGm//BTAC/G2K4zDHf@public.gmane.org>
2014-12-18 22:01         ` Scott Wood
     [not found]           ` <1418940078.5581.143.camel-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
2014-12-19  7:23             ` Shaohui Xie
     [not found]               ` <DM2PR0301MB0864AA31CD1A7438F476020FE26B0-Cwg/PA1lyPnq20u2fDgSrZwN6zqB+hSMnBOFsp37pqbUKgpGm//BTAC/G2K4zDHf@public.gmane.org>
2014-12-19 23:15                 ` Scott Wood
2014-12-22  2:31                   ` Shaohui Xie
     [not found]                     ` <DM2PR0301MB086427C10254A0A749CD1326E2560-Cwg/PA1lyPnq20u2fDgSrZwN6zqB+hSMnBOFsp37pqbUKgpGm//BTAC/G2K4zDHf@public.gmane.org>
2014-12-22  8:20                       ` Emil Medve
     [not found]                         ` <5497D466.9090804-eDlz3WWmN0ll57MIdRCFDg@public.gmane.org>
2014-12-22  8:32                           ` Scott Wood
     [not found]                             ` <1419237176.5581.159.camel-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
2014-12-22  8:56                               ` Shaohui Xie
2014-12-22  9:37                               ` Emil Medve
     [not found]                                 ` <5497E645.7010500-eDlz3WWmN0ll57MIdRCFDg@public.gmane.org>
2014-12-22  9:42                                   ` Scott Wood
     [not found]                                     ` <1419241330.5581.162.camel-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
2014-12-22 11:08                                       ` Emil Medve [this message]
     [not found]                                         ` <5497FBAB.4010206-eDlz3WWmN0ll57MIdRCFDg@public.gmane.org>
2014-12-22 21:25                                           ` Scott Wood
     [not found]                                             ` <1419283551.5581.172.camel-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
2014-12-23  7:35                                               ` Shaohui Xie
     [not found]                                                 ` <DM2PR0301MB08642FFDB6207DE205731547E2570-Cwg/PA1lyPnq20u2fDgSrZwN6zqB+hSMnBOFsp37pqbUKgpGm//BTAC/G2K4zDHf@public.gmane.org>
2014-12-23  8:08                                                   ` Scott Wood
     [not found]                                                     ` <1419322085.5581.182.camel-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
2014-12-23  8:17                                                       ` Shaohui Xie

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