netdev - Re: [PATCH v1 5/7] ARM i.MX6q: remove Atheros AR8035 SmartEEE fixup

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Date:   Mon, 8 Feb 2021 14:21:09 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, Sascha Hauer <s.hauer@...gutronix.de>,
        linux-kernel@...r.kernel.org,
        Philippe Schenker <philippe.schenker@...adex.com>,
        linux-imx@....com, kernel@...gutronix.de,
        David Jander <david@...tonic.nl>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH v1 5/7] ARM i.MX6q: remove Atheros AR8035 SmartEEE fixup

On Mon, Feb 08, 2021 at 10:20:38AM +0100, Oleksij Rempel wrote:
> On Wed, Feb 03, 2021 at 09:56:28AM +0000, Russell King - ARM Linux admin wrote:
> > That is the historical fix for this problem, but there is a better
> > solution now in net-next - configuring the Tw parameter for gigabit
> > connections. That solves the random link drop issue when EEE is
> > enabled.
> 
> Do you mean this properties?
>   qca,smarteee-tw-us-1g
>   qca,smarteee-tw-us-100m
> 
> Do you have some recommendations, which values can be here used? Are
> they same for all MACs? Or, can we calculate this values automatically?

I don't think there's a way to "calculate" them.

The AR8035 default is 17us for 1G and 23us for 100M. Increasing the
1G Tw to 26us or 27us fixes it on several different Solidrun platforms
(iMX6 Hummingboards and Cubox-i, and LX2160A based). The boards all
have differing layouts, so I don't think it's layout or SoC specific
(which is good news.)

These figures have been arrived at by repetitive long-term testing and
observing whether there are sporadic link drops over these platforms.

> Beside, I have seen this patch: "ARM: dts: imx6qdl-sr-som: fix some
> cubox-i platforms"

That's for a different problem: moving these settings to DT broke
some Cubox-i platforms because of the weird ways that the AR8035
configures the address bits, using the LED pin. Tying a LED to the
LED pin is not sufficient to guarantee that a board always configures
the PHY to a particular address, so it can appear on address 0 or 4
depending on noise, temperature, supply voltage, and PHY chip
thresholds.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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