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Date:   Wed, 26 Oct 2022 14:05:25 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Maxime Chevallier <maxime.chevallier@bootlin.com>
Cc:     Sean Anderson <seanga2@gmail.com>, davem@davemloft.net,
        Rob Herring <robh+dt@kernel.org>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com,
        Jakub Kicinski <kuba@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        linux-arm-kernel@lists.infradead.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        devicetree@vger.kernel.org
Subject: Re: [PATCH net-next v3 3/5] net: pcs: add new PCS driver for altera
 TSE PCS
Message-ID: <Y1kihVfwglzOD2uE@lunn.ch>
References: <20220901143543.416977-1-maxime.chevallier@bootlin.com>
 <20220901143543.416977-4-maxime.chevallier@bootlin.com>
 <68b3dfbf-9bab-2554-254e-bffd280ba97e@gmail.com>
 <20221026113711.2b740c7a@pc-8.home>
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> > > +	/* This PCS seems to require a soft reset to re-sync the
> > > AN logic */
> > > +	tse_pcs_reset(tse_pcs);  
> > 
> > This is kinda strange since c22 phys are supposed to reset the other
> > registers to default values when BMCR_RESET is written. Good thing
> > this is a PCS...
> 
> Indeed. This soft reset will not affect the register configuration, it
> will only reset all internal state machines.
> 
> The datasheet actually recommends performing a reset after any
> configuration change...

The Marvell PHYs work like this. Many of its registers won't take
effect until you do a soft reset. I think the thinking behind this is
that changing many registers is disruptive to the link and slow. It
takes over a second to perform auto-neg etc. So ideally you want to
make all your register changes, and then trigger them into operation.
And a soft reset is this trigger.

    Andrew