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 09:51:57 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Andrew Lunn <andrew@...n.ch>
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

Andrew

On 5/27/20 8:12 AM, Andrew Lunn wrote:
>> 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.

OK.  I guess then the DP83867 driver is wrong because it specifically 
states in bold

     /* RX delay *must* be specified if internal delay of RX is used. */

It was signed off in commit fafc5db28a2ff


>>>> +	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.

Actually I will be removing this check with setting the delays to default.

Dan


>      Andrew