netdev - Re: [PATCH net-next 0/4] net: phy: mscc-miim: reduce waiting time between MDIO transactions

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Message-ID: <20200526170100.GM768009@lunn.ch>
Date:   Tue, 26 May 2020 19:01:00 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Antoine Tenart <antoine.tenart@...tlin.com>
Cc:     davem@...emloft.net, f.fainelli@...il.com, hkallweit1@...il.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        alexandre.belloni@...tlin.com, thomas.petazzoni@...tlin.com,
        allan.nielsen@...rochip.com
Subject: Re: [PATCH net-next 0/4] net: phy: mscc-miim: reduce waiting time
 between MDIO transactions

On Tue, May 26, 2020 at 06:22:52PM +0200, Antoine Tenart wrote:
> Hello,
> 
> This series aims at reducing the waiting time between MDIO transactions
> when using the MSCC MIIM MDIO controller.

Hi Antoine

There are a couple of other things you can look at:

Can you disable the pre-amble on the MDIO transaction. It requires
that both the bus master and all devices on the bus support it, but
when it is usable, you half the number of bits sent over the wire.

Can you control the frequency of MDC? 802.3 says 2.5MHz, but many
devices support higher speeds. Again, you need all devices on the bus
to support the speed.

When accessing raw TDR data for cable tests i also have a lot of PHY
accesses. I implemented both of these for the FEC MDIO bus, and made
it a lot faster.

   Andrew