linux-kernel - Re: [PATCH net-next v2 6/6] net: phy: microchip_t1s: add support for Microchip LAN865x Rev.B0 PHYs

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Message-ID: <819531cd-ebd7-4734-b35b-8f8c3d138004@lunn.ch>
Date:   Tue, 23 May 2023 14:29:21 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Parthiban.Veerasooran@...rochip.com
Cc:     hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ramon.nordin.rodriguez@...roamp.se, Horatiu.Vultur@...rochip.com,
        Woojung.Huh@...rochip.com, Nicolas.Ferre@...rochip.com,
        Thorsten.Kummermehr@...rochip.com
Subject: Re: [PATCH net-next v2 6/6] net: phy: microchip_t1s: add support for
 Microchip LAN865x Rev.B0 PHYs

> > Is this doing a read from fuses? Is anything documented about this?
> > What the values mean? Would a board designer ever need to use
> > different values? Or is this just a case of 'trust us', you don't need
> > to understand this magic.
> Yes, it is a read from fuses and those values are specific/unique for 
> each PHY chip. Those values are calculated based on some characteristics 
> of the PHY chip behavior for optimal performance and they are fused in 
> the PHY chip for the driver to configure it during the initialization. 
> This is done in the production/testing stage of the PHY chip. As it is 
> specific to PHY chip, a board designer doesn't have any influence on 
> this and need not to worry about it. Unfortunately they can't be 
> documented anywhere as they are design specific. So simply 'trust us'.

O.K. Please consider for future generations that you move all this
magic into the PHY firmware. There does not seem to be any reason the
OS needs to know about this.

     Andrew