linux-kernel - Re: [PATCH net-next v3 4/4] net: dp83869: Add RGMII internal delay configuration

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Date:   Wed, 27 May 2020 15:12:04 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Dan Murphy <dmurphy@...com>
Cc:     f.fainelli@...il.com, hkallweit1@...il.com, davem@...emloft.net,
        robh@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v3 4/4] net: dp83869: Add RGMII internal delay
 configuration

> If the dt defines rgmii-rx/tx-id then these values are required not
> optional.  That was the discussion on the binding.

How many times do i need to say it. They are optional. If not
specified, default to 2ns.

> > > +	ret = of_property_read_u32(of_node, "tx-internal-delay-ps",
> > > +				   &dp83869->tx_id_delay);
> > > +	if (ret) {
> > > +		dp83869->tx_id_delay = ret;
> > > +		ret = 0;
> > > +	}
> > > +
> > >   	return ret;
> > >   }
> > >   #else
> > > @@ -367,10 +388,45 @@ static int dp83869_configure_mode(struct phy_device *phydev,
> > >   	return ret;
> > >   }
> > > +static int dp83869_get_delay(struct phy_device *phydev)
> > > +{
> > > +	struct dp83869_private *dp83869 = phydev->priv;
> > > +	int delay_size = ARRAY_SIZE(dp83869_internal_delay);
> > > +	int tx_delay = 0;
> > > +	int rx_delay = 0;
> > > +
> > > +	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID ||
> > > +	    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID) {
> > > +		tx_delay = phy_get_delay_index(phydev,
> > > +					       &dp83869_internal_delay[0],
> > > +					       delay_size, dp83869->tx_id_delay,
> > > +					       false);
> > > +		if (tx_delay < 0) {
> > > +			phydev_err(phydev, "Tx internal delay is invalid\n");
> > > +			return tx_delay;
> > > +		}
> > > +	}
> > > +
> > > +	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID ||
> > > +	    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID) {
> > > +		rx_delay = phy_get_delay_index(phydev,
> > > +					       &dp83869_internal_delay[0],
> > > +					       delay_size, dp83869->rx_id_delay,
> > > +					       false);
> > > +		if (rx_delay < 0) {
> > > +			phydev_err(phydev, "Rx internal delay is invalid\n");
> > > +			return rx_delay;
> > > +		}
> > > +	}
> > So any PHY using these properties is going to pretty much reproduce
> > this code. Meaning is should all be in a helper.
> 
> The issue here is that the phy_mode may only be rgmii-txid so you only want
> to find the tx_delay and return.
> 
> Same with the RXID.  How is the helper supposed to know what delay to return
> and look for?

How does this code do it? It looks at the value of interface.

    Andrew