netdev - Re: [net-next RFC PATCH v2 01/11] net: phy: extend PHY package API to support multiple global address

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Message-ID: <656237d6.5d0a0220.2c3da.d832@mx.google.com>
Date: Sat, 25 Nov 2023 15:24:53 +0100
From: Christian Marangi <ansuelsmth@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: "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>, Andy Gross <agross@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Daniel Golle <daniel@...rotopia.org>,
	Qingfang Deng <dqfext@...il.com>,
	SkyLake Huang <SkyLake.Huang@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Vladimir Oltean <olteanv@...il.com>,
	David Epping <david.epping@...singlinkelectronics.com>,
	Harini Katakam <harini.katakam@....com>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Robert Marko <robert.marko@...tura.hr>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [net-next RFC PATCH v2 01/11] net: phy: extend PHY package API
 to support multiple global address

On Sat, Nov 25, 2023 at 06:51:54PM +0100, Andrew Lunn wrote:
> On Sat, Nov 25, 2023 at 01:11:17AM +0100, Christian Marangi wrote:
> > Current API for PHY package are limited to single address to configure
> > global settings for the PHY package.
> > 
> > It was found that some PHY package (for example the qca807x, a PHY
> > package that is shipped with a bundle of 5 PHY) require multiple PHY
> > address to configure global settings. An example scenario is a PHY that
> > have a dedicated PHY for PSGMII/serdes calibrarion and have a specific
> > PHY in the package where the global PHY mode is set and affects every
> > other PHY in the package.
> > 
> > Change the API in the following way:
> > - Make phy_package_join() require a list of address to be passed and the
> >   number of address in the list
> > - On shared data init, each address is the list is checked and added to
> >   the shared struct.
> > - Make __/phy_package_write/read() require an additional arg that
> >   select what global PHY address to use in the provided list.
> 
> I think this is overly complex.
> 
> I would rename struct phy_package_shared addr to base_addr.
> phy_package_join() would then pass the base address of the package,
> which is the same as your reg property for the package in DT.
> 
> I think all current users of devm_phy_package_join() already do pass
> the lowest address in the package, so this should not cause any
> problems. Most drivers even call it base address, rather than cookie,
> which the documentation uses.
> 
> I would then extend __phy_package_read() etc to take an offset, which
> is added to base_addr, and the read is performed on that address. All
> the existing users would pass 0, and your new driver can pass other
> values.
> 
> I also think you can split this out from the DT binding. Make it two
> patch sets. One patch set is about extended the package concept to
> allow access to global registers at addresses other than the base. The
> DT patch is about properties which are shared by the package. These
> seems like two mostly orthogonal concepts.
>

Yes can be detached. Making addr to base_addr would change the thing but
can confirm, any user of the API always used the base addr as cookie, so
it won't change a thing.

Will have to make the separate commit a dependency to this series but i
expect this change to be merged before this RFC is completed. Good idea.

-- 
	Ansuel