linux-kernel - Re: [net-next,PATCH 4/4] dt-bindings: mdio-ipq4019: add clock support

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Message-ID: <42ebc500-35ba-48f6-c4d1-3743abde1852@gmail.com>
Date:   Thu, 2 Jul 2020 13:04:37 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Robert Marko <robert.marko@...tura.hr>,
        Andrew Lunn <andrew@...n.ch>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        David Miller <davem@...emloft.net>, kuba@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        robh+dt@...nel.org
Subject: Re: [net-next,PATCH 4/4] dt-bindings: mdio-ipq4019: add clock support



On 7/2/2020 12:18 PM, Robert Marko wrote:
> On Thu, Jul 2, 2020 at 3:38 PM Andrew Lunn <andrew@...n.ch> wrote:
>>
>>> +  clock-frequency:
>>> +    default: 100000000
>>
>> IEEE 802.3 says the default should be 2.5MHz. Some PHYs will go
>> faster, but 100MHz seems unlikely!
> This MDIO controller has an internal divider, by default its set for
> 100MHz clock.
> In IPQ4019 MDIO clock is not controllable but in IPQ6018 etc it's controllable.
> That is the only combination I have currently seen used by Qualcomm.

Not sure I understand here, the 'clock-frequency' is supposed to denote
the MDIO bus output clock frequency, that is the frequency at which all
MDIO devices are going to operate at. Is this 100MHz a clock that feeds
into the MDIO block and get internally divided by a programmable
register to obtain an output MDIO clock?
-- 
Florian