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From: Andrew Lunn <andrew@lunn.ch>
To: Florian Fainelli <f.fainelli@gmail.com>
Cc: Adrien Grassein <adrien.grassein@gmail.com>,
	fugang.duan@nxp.com, davem@davemloft.net, kuba@kernel.org,
	robh+dt@kernel.org, netdev@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/3] dt-bindings: net: fsl-fec add mdc/mdio bitbang option
Date: Mon, 30 Nov 2020 23:26:45 +0100	[thread overview]
Message-ID: <20201130222645.GG2073444@lunn.ch> (raw)
In-Reply-To: <bb81c90c-d79e-d944-e35e-305da23d9e58@gmail.com>

> >> I am currently upstreaming the "Nitrogen 8m Mini board" that seems to not use a
> >> "normal" mdio bus but a "bitbanged" one with the fsl fec driver.
> > 
> > Any idea why?
> > 
> > Anyway, you should not replicate code, don't copy bitbanging code into
> > the FEC. Just use the existing bit-banger MDIO bus master driver.
> 
> Right there should be no need for you to modify the FEC driver at all,
> there is an existing generic bitbanged MDIO bus driver here:

Hi Florian

Speculation on my part, until i hear back on the Why? question, but
i'm guessing the board has a wrong pullup on the MDIO line. It takes
too long for the PHY/FEC to pull the line low at the default
2.5MHz. bit-banging is much slower, so it works.

If i'm right, there is a much simpler fix for this. Use the
clock-frequency property for the MDIO bus to slow the clock down.

	Andrew

  reply	other threads:[~2020-11-30 22:27 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-28 22:54 [PATCH " Adrien Grassein
2020-11-28 22:54 ` [PATCH 2/3] net: fsl: fec: " Adrien Grassein
2020-11-28 22:54 ` [PATCH 3/3] net: fsl: fec: add imx8mq support Adrien Grassein
2020-11-29 21:59 ` [PATCH v2 1/3] dt-bindings: net: fsl-fec add mdc/mdio bitbang option Adrien Grassein
2020-11-29 21:59   ` [PATCH v2 2/3] net: fsl: fec: " Adrien Grassein
2020-11-29 22:00   ` [PATCH v2 3/3] net: fsl: fec: add imx8mq support Adrien Grassein
     [not found]   ` <20201129224113.GS2234159@lunn.ch>
     [not found]     ` <CABkfQAFcSNMeYEepsx0Z6tuaif-dQhE2YBMK54t1hikAvzdASg@mail.gmail.com>
2020-11-29 23:04       ` [PATCH v2 1/3] dt-bindings: net: fsl-fec add mdc/mdio bitbang option Andrew Lunn
2020-11-30 22:08         ` Florian Fainelli
2020-11-30 22:26           ` Andrew Lunn [this message]
2020-12-04 20:09             ` Adrien Grassein

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