linux-kernel - Re: [PATCH net-next 3/3] net: fec: reset phy on resume after power-up

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Message-ID: <20211215194855.GA114534@francesco-nb.int.toradex.com>
Date:   Wed, 15 Dec 2021 20:48:55 +0100
From:   Francesco Dolcini <francesco.dolcini@...adex.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Francesco Dolcini <francesco.dolcini@...adex.com>,
        "Russell King (Oracle)" <linux@...linux.org.uk>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Philippe Schenker <philippe.schenker@...adex.com>,
        netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 3/3] net: fec: reset phy on resume after power-up

On Wed, Dec 15, 2021 at 08:34:00PM +0100, Andrew Lunn wrote:
> > The reason is that the power consumption in reset is higher in reset
> > compared to the normal PHY software power down.
> 
> Does the datasheet have numbers for in lower power mode and held in
> reset? We only have an issue if held in reset when in low power mode
> consumes more power than simply in low power mode.

The numbers for KSZ9131, Table 6-3: Power Consumption from datasheet [0]

61.2mW in reset, 24.4mW in software power down (3.3VDD)
40.9mW in reset, 12.5mW in software power down (2.5VDD)

Francesco

[0] https://ww1.microchip.com/downloads/en/DeviceDoc/00002841B.pdf