linux-kernel - Re: [PATCH 2/2] net: phy: realtek: Add optional external PHY clock

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Message-ID: <94d74b65-55ad-d070-2590-d21b79ff5abb@gmail.com>
Date:   Thu, 1 Jun 2023 13:14:27 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Detlev Casanova <detlev.casanova@...labora.com>
Cc:     linux-kernel@...r.kernel.org,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] net: phy: realtek: Add optional external PHY clock

On 6/1/23 12:37, Andrew Lunn wrote:
>> I'm not sure about this. Isn't the clock still necessary when suspended for
>> things like wake on lan ?
> 
> Yes, but the PHY should know if its a WoL source, and not disable its
> own clock. There is some support for this in phylib, and Florian has
> also reworked it recently for Broadcom PHYs.

If you want to have the PHY driver have a chance to disable the clock if 
Wake-on-LAN is disabled and therefore conserve power, you should set 
PHY_ALWAYS_CALL_SUSPEND in the phy_driver::flags and in the 
suspend/resume functions do something like:

suspend:
	/* last step after all registers are accessed */
	if (!phydev->wol_enabled)
		clk_disable_unprepare()
resume:
	/* first step before registers are accessed */
	if (!phydev->wol_enabled)
		clk_prepare_enable()

The flag is necessary to ensure that the PHY driver's suspend function 
will be called. The resume will be called regardless of Wake-on-LAN 
being enabled or not.
-- 
Florian