netdev - Re: [RFC PATCH v2 net-next 01/15] phy: introduce phy_get

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Date: Mon, 2 Oct 2023 12:16:12 -0700
From: Florian Fainelli <f.fainelli@...il.com>
To: Vladimir Oltean <vladimir.oltean@....com>, netdev@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-phy@...ts.infradead.org
Cc: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
 Heiner Kallweit <hkallweit1@...il.com>, Andrew Lunn <andrew@...n.ch>,
 Madalin Bucur <madalin.bucur@....com>, Ioana Ciornei
 <ioana.ciornei@....com>, Camelia Groza <camelia.groza@....com>,
 Li Yang <leoyang.li@....com>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor@...nel.org>, Sean Anderson <sean.anderson@...o.com>,
 Maxime Chevallier <maxime.chevallier@...tlin.com>,
 Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>
Subject: Re: [RFC PATCH v2 net-next 01/15] phy: introduce phy_get_status() and
 use it to report CDR lock

On 9/23/23 06:48, Vladimir Oltean wrote:
> Some modules, like the MTIP AN/LT block used as a copper backplane PHY
> driver, need this extra information from the SerDes PHY as another
> source of "link up" information.
> 
> Namely, the 25GBase-R PCS does not have a MDIO_CTRL1_LPOWER bit
> implemented in its MDIO_MMD_PCS:MDIO_CTRL1 register. That bit is
> typically set from phy_suspend() or phylink_pcs_disable() implementations,
> and that is supposed to cause a link drop event on the link partner.
> But here it does not happen.
> 
> By implementing the networking phylink_pcs_disable() as phy_power_off(),
> we are able to actually power down the lane in a way that is visible to
> the remote end. Where it is visible is the CDR lock, so we introduce
> PHY_STATUS_TYPE_CDR_LOCK as an extra link indication, we are able to
> detect that condition and signal it to upper layers of the network
> stack.
> 
> A more high-level and generic phy_get_status() operation was chosen
> instead of the more specific phy_get_cdr_lock() alternative, because I
> saw this as being more in the spirit of the generic PHY API.
> Also, phy_get_status() is more extensible and reusable for other
> purposes as well.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
-- 
Florian