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

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Date: Thu, 01 Jun 2023 14:53:02 -0400
From: Detlev Casanova <detlev.casanova@...labora.com>
To: linux-kernel@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, 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>, Florian Fainelli <f.fainelli@...il.com>,
 netdev@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] net: phy: realtek: Add optional external PHY clock

On Wednesday, May 31, 2023 3:08:53 P.M. EDT Heiner Kallweit wrote:
> On 31.05.2023 17:03, Detlev Casanova wrote:
> > In some cases, the PHY can use an external clock source instead of a
> > crystal.
> > 
> > Add an optional clock in the phy node to make sure that the clock source
> > is enabled, if specified, before probing.
> > 
> > Signed-off-by: Detlev Casanova <detlev.casanova@...labora.com>
> > ---
> > 
> >  drivers/net/phy/realtek.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
> > index 3d99fd6664d7..70c75dbbf799 100644
> > --- a/drivers/net/phy/realtek.c
> > +++ b/drivers/net/phy/realtek.c
> > @@ -12,6 +12,7 @@
> > 
> >  #include <linux/phy.h>
> >  #include <linux/module.h>
> >  #include <linux/delay.h>
> > 
> > +#include <linux/clk.h>
> > 
> >  #define RTL821x_PHYSR				0x11
> >  #define RTL821x_PHYSR_DUPLEX			BIT(13)
> > 
> > @@ -80,6 +81,7 @@ struct rtl821x_priv {
> > 
> >  	u16 phycr1;
> >  	u16 phycr2;
> >  	bool has_phycr2;
> > 
> > +	struct clk *clk;
> > 
> >  };
> >  
> >  static int rtl821x_read_page(struct phy_device *phydev)
> > 
> > @@ -103,6 +105,11 @@ static int rtl821x_probe(struct phy_device *phydev)
> > 
> >  	if (!priv)
> >  	
> >  		return -ENOMEM;
> > 
> > +	priv->clk = devm_clk_get_optional_enabled(dev, "xtal");
> 
> Why add priv->clk if it isn't used outside probe()?
> 
> How about suspend/resume? Would it make sense to stop the clock
> whilst PHY is suspended?

I'm not sure about this. Isn't the clock still necessary when suspended for 
things like wake on lan ?

> > +	if (IS_ERR(priv->clk))
> > +		return dev_err_probe(dev, PTR_ERR(priv->clk),
> > +				     "failed to get phy xtal 
clock\n");
> > +
> > 
> >  	ret = phy_read_paged(phydev, 0xa43, RTL8211F_PHYCR1);
> >  	if (ret < 0)
> >  	
> >  		return ret;