netdev - Re: [PATCH] net: phy: at803x: disable delay only for RGMII mode

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Date:   Wed, 13 Feb 2019 18:40:34 +0100
From:   Niklas Cassel <niklas.cassel@...aro.org>
To:     Marc Gonzalez <marc.w.gonzalez@...e.fr>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vinod Koul <vkoul@...nel.org>,
        David S Miller <davem@...emloft.net>,
        linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        netdev@...r.kernel.org, "Nori, Sekhar" <nsekhar@...com>,
        Peter Ujfalusi <peter.ujfalusi@...com>
Subject: Re: [PATCH] net: phy: at803x: disable delay only for RGMII mode

On Wed, Feb 13, 2019 at 02:40:18PM +0100, Marc Gonzalez wrote:
> On 13/02/2019 14:29, Andrew Lunn wrote:
> 
> >> So we have these modes:
> >>
> >> PHY_INTERFACE_MODE_RGMII: TX and RX delays disabled
> >> PHY_INTERFACE_MODE_RGMII_ID: TX and RX delays enabled
> >> PHY_INTERFACE_MODE_RGMII_RXID: RX delay enabled, TX delay disabled
> >> PHY_INTERFACE_MODE_RGMII_TXID: TX delay enabled, RX delay disabled
> >>
> >> What I don't like with this patch, is that if we specify phy-mode
> >> PHY_INTERFACE_MODE_RGMII_TXID, this patch will enable TX delay,
> >> but RX delay will not be explicitly set.
> > 
> > That is not the behaviour we want. It is best to assume the device is
> > in a random state, and correctly enable/disable all delays as
> > requested. Only leave the hardware alone if PHY_INTERFACE_MODE_NA is
> > used.
> 
> That's what my patch did:
> https://www.spinics.net/lists/netdev/msg445053.html
> 
> But see Florian's remarks:
> https://www.spinics.net/lists/netdev/msg445133.html

Hello Marc,

I saw that comment from Florian. However that was way back in 2017.
Maybe the phy-modes were not as well defined back then?

Andrew recently suggested to fix the driver so that it conforms with the
phy-modes, and fix any SoC that specified an incorrect phy-mode in DT
and thus relied upon the broken behavior of the PHY driver:
https://www.spinics.net/lists/netdev/msg445133.html


So, I've rebased your old patch, see attachment.
I suggest that Peter test it on am335x-evm.

am335x-evm appears to rely on the current broken behavior of the PHY
driver, so we will probably need to fix the am335x-evm according to this:
https://www.spinics.net/lists/netdev/msg445117.html
and merge that as well.


Andrew, Florian, do you both agree?


Kind regards,
Niklas

View attachment "0001-net-phy-at803x-Fix-RGMII-RX-and-TX-clock-delays-setu.patch" of type "text/plain" (2912 bytes)