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

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Message-ID: <4a6c413c-8791-fd00-a73e-7a12413693e3@gmail.com>
Date: Wed, 31 May 2023 21:08:53 +0200
From: Heiner Kallweit <hkallweit1@...il.com>
To: Detlev Casanova <detlev.casanova@...labora.com>,
 linux-kernel@...r.kernel.org
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 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?

> +	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;