linux-kernel - Re: [net-next PATCH 1/3] net: phy: extend PHY package API to support multiple global address

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Message-ID: <65638967.5d0a0220.28475.43b3@mx.google.com>
Date:   Sun, 26 Nov 2023 19:07:32 +0100
From:   Christian Marangi <ansuelsmth@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <florian.fainelli@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        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>,
        Vladimir Oltean <olteanv@...il.com>,
        David Epping <david.epping@...singlinkelectronics.com>,
        Harini Katakam <harini.katakam@....com>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH 1/3] net: phy: extend PHY package API to support
 multiple global address

On Sun, Nov 26, 2023 at 07:04:26PM +0100, Andrew Lunn wrote:
> > @@ -1648,20 +1648,27 @@ EXPORT_SYMBOL_GPL(phy_driver_is_genphy_10g);
> >  /**
> >   * phy_package_join - join a common PHY group
> >   * @phydev: target phy_device struct
> > - * @addr: cookie and PHY address for global register access
> > + * @base_addr: cookie and base PHY address of PHY package for offset
> > + *   calculation of global register access
> >   * @priv_size: if non-zero allocate this amount of bytes for private data
> >   *
> >   * This joins a PHY group and provides a shared storage for all phydevs in
> >   * this group. This is intended to be used for packages which contain
> >   * more than one PHY, for example a quad PHY transceiver.
> >   *
> > - * The addr parameter serves as a cookie which has to have the same value
> > - * for all members of one group and as a PHY address to access generic
> > - * registers of a PHY package. Usually, one of the PHY addresses of the
> > - * different PHYs in the package provides access to these global registers.
> > + * The addr parameter serves as cookie which has to have the same values
> 
> addr has been renamed base_addr.
> 
> > + * for all members of one group and as the base PHY address of the PHY package
> > + * for offset calculation to access generic registers of a PHY package.
> > + * Usually, one of the PHY addresses of the different PHYs in the package
> > + * provides access to these global registers.
> >   * The address which is given here, will be used in the phy_package_read()
> > - * and phy_package_write() convenience functions. If your PHY doesn't have
> > - * global registers you can just pick any of the PHY addresses.
> > + * and phy_package_write() convenience functions as base and added to the
> > + * passed offset in those functions. If your PHY doesn't have global registers
> > + * you can just pick any of the PHY addresses.
> 
> 
> I would not add this last sentence. We want a clearly defined meaning
> of base_addr. Its the lowest address in the package. It does not
> matter if its not used, it should still be the lowest address in the
> package.
> 
> > + * In some special PHY package, multiple PHY are used for global init of
> 
> I don't see why they are special.
> 
> > -static inline int phy_package_read(struct phy_device *phydev, u32 regnum)
> > +static inline int phy_package_read(struct phy_device *phydev,
> > +				   unsigned int addr_offset, u32 regnum)
> >  {
> >  	struct phy_package_shared *shared = phydev->shared;
> > +	int addr;
> >  
> > -	if (!shared)
> > +	if (!shared || shared->base_addr + addr_offset > PHY_MAX_ADDR)
> >  		return -EIO;
> >  
> > -	return mdiobus_read(phydev->mdio.bus, shared->addr, regnum);
> > +	addr = shared->base_addr + addr_offset;
> > +	return mdiobus_read(phydev->mdio.bus, addr, regnum);
> 
> This might be a little bit more readable:
> 
> static inline int phy_package_read(struct phy_device *phydev,
> 				   unsigned int addr_offset, u32 regnum)
> {
> 	struct phy_package_shared *shared = phydev->shared;
> 	int addr = shared->base_addr + addr_offset;

Isn't this problematic if shared is NULL?

I can add 2 if condition and set addr in between only after shared not
NULL check is done?

> 
> 	if (!shared)
> 	if (!shared || addr > PHY_MAX_ADDR)
> 		return -EIO;
> 
> 	return mdiobus_read(phydev->mdio.bus, addr, regnum);
> }
> 
>

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