linux-kernel - Re: [PATCH 1/2] net: phy: micrel.c: add rgmii interface delay possibility to ksz9131

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Date:   Wed, 25 Mar 2020 15:47:32 +0000
From:   Philippe Schenker <philippe.schenker@...adex.com>
To:     "andrew@...n.ch" <andrew@...n.ch>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
CC:     "o.rempel@...gutronix.de" <o.rempel@...gutronix.de>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "a.fatoum@...gutronix.de" <a.fatoum@...gutronix.de>,
        "silvan.murer@...il.com" <silvan.murer@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [PATCH 1/2] net: phy: micrel.c: add rgmii interface delay
 possibility to ksz9131

On Wed, 2020-03-25 at 16:24 +0100, Heiner Kallweit wrote:
> On 25.03.2020 16:03, Philippe Schenker wrote:
> > The KSZ9131 provides DLL controlled delays on RXC and TXC lines.
> > This
> > patch makes use of those delays. The information which delays should
> > be enabled or disabled comes from the interface names, documented in
> > ethernet-controller.yaml:
> > 
> > rgmii:      Disable RXC and TXC delays
> > rgmii-id:   Enable RXC and TXC delays
> > rgmii-txid: Enable only TXC delay, disable RXC delay
> > rgmii-rxid: Enable onlx RXC delay, disable TXC delay
> > 
> > Signed-off-by: Philippe Schenker <philippe.schenker@...adex.com>
> > ---
> > 
> >  drivers/net/phy/micrel.c | 45
> > ++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 45 insertions(+)
> > 
> > diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
> > index 63dedec0433d..d3ad09774847 100644
> > --- a/drivers/net/phy/micrel.c
> > +++ b/drivers/net/phy/micrel.c
> > @@ -704,6 +704,48 @@ static int ksz9131_of_load_skew_values(struct
> > phy_device *phydev,
> >  	return phy_write_mmd(phydev, 2, reg, newval);
> >  }
> >  
> > +/* MMD Address 0x2 */
> > +#define KSZ9131RN_RXC_DLL_CTRL		76
> > +#define KSZ9131RN_TXC_DLL_CTRL		77
> > +#define KSZ9131RN_DLL_CTRL_BYPASS	BIT_MASK(12)
> > +#define KSZ9131RN_DLL_ENABLE_DELAY	0
> > +#define KSZ9131RN_DLL_DISABLE_DELAY	BIT(12)
> > +
> > +static int ksz9131_config_rgmii_delay(struct phy_device *phydev)
> > +{
> > +	int ret;
> > +	u16 rxcdll_val, txcdll_val;
> > +
> 
> Reverse xmas tree order please.
> 
> > +	switch (phydev->interface) {
> > +	case PHY_INTERFACE_MODE_RGMII:
> > +		rxcdll_val = KSZ9131RN_DLL_DISABLE_DELAY;
> > +		txcdll_val = KSZ9131RN_DLL_DISABLE_DELAY;
> > +		break;
> > +	case PHY_INTERFACE_MODE_RGMII_ID:
> > +		rxcdll_val = KSZ9131RN_DLL_ENABLE_DELAY;
> > +		txcdll_val = KSZ9131RN_DLL_ENABLE_DELAY;
> > +		break;
> > +	case PHY_INTERFACE_MODE_RGMII_RXID:
> > +		rxcdll_val = KSZ9131RN_DLL_ENABLE_DELAY;
> > +		txcdll_val = KSZ9131RN_DLL_DISABLE_DELAY;
> > +		break;
> > +	case PHY_INTERFACE_MODE_RGMII_TXID:
> > +		rxcdll_val = KSZ9131RN_DLL_DISABLE_DELAY;
> > +		txcdll_val = KSZ9131RN_DLL_ENABLE_DELAY;
> > +		break;
> > +	default:
> > +		return 0;
> > +	}
> > +
> > +	ret = phy_modify_mmd_changed(phydev, 2, KSZ9131RN_RXC_DLL_CTRL,
> > +				     KSZ9131RN_DLL_CTRL_BYPASS,
> > rxcdll_val);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return phy_modify_mmd_changed(phydev, 2, KSZ9131RN_TXC_DLL_CTRL,
> > +				     KSZ9131RN_DLL_CTRL_BYPASS,
> > txcdll_val);
> 
> phy_modify_mmd_changed() returns 1 if the register value was changed,
> and that's not what you want here. Simply use phy_modify_mmd() in both
> occurrences. And your function has a return value, but it's not used
> by
> the caller.

Thanks for your feedback, I'll send a v2 with those fixes.
> 
> > +}
> > +
> >  static int ksz9131_config_init(struct phy_device *phydev)
> >  {
> >  	const struct device *dev = &phydev->mdio.dev;
> > @@ -730,6 +772,9 @@ static int ksz9131_config_init(struct phy_device
> > *phydev)
> >  	if (!of_node)
> >  		return 0;
> >  
> > +	if (phy_interface_is_rgmii(phydev))
> > +		ksz9131_config_rgmii_delay(phydev);
> > +
> >  	ret = ksz9131_of_load_skew_values(phydev, of_node,
> >  					  MII_KSZ9031RN_CLK_PAD_SKEW, 5,
> >  					  clk_skews, 2);
> >