linux-kernel - Re: [EXTERNAL] Re: [PATCH v4 2/2] net: ti: icssg-prueth: Add ICSSG ethernet driver

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Message-ID: <42503a0d-b434-bbcc-553d-a326af5b4918@ti.com>
Date:   Tue, 7 Feb 2023 20:59:35 +0530
From:   Md Danish Anwar <a0501179@...com>
To:     Andrew Lunn <andrew@...n.ch>, MD Danish Anwar <danishanwar@...com>
CC:     "Andrew F. Davis" <afd@...com>, Suman Anna <s-anna@...com>,
        Roger Quadros <rogerq@...nel.org>,
        YueHaibing <yuehaibing@...wei.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>, <nm@...com>,
        <ssantosh@...nel.org>, <srk@...com>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-omap@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [EXTERNAL] Re: [PATCH v4 2/2] net: ti: icssg-prueth: Add ICSSG
 ethernet driver

Hi Andrew,

On 06/02/23 19:45, Andrew Lunn wrote:
>> +enum mii_mode {
>> +	MII_MODE_MII = 0,
>> +	MII_MODE_RGMII,
>> +	MII_MODE_SGMII
> 
> There is no mention of SGMII anywhere else. And in a couple of places,
> the code makes the assumption that if it is not RGMII it is MII.
> 
> Does the hardware really support SGMII?
> 

As far as I know, the hardware does support SGMII but it's not yet supported by
the driver. I will drop the SGMII because it's not needed as of now. If in
future support for SGMII is there, I'll add it.

>> +static int prueth_config_rgmiidelay(struct prueth *prueth,
>> +				    struct device_node *eth_np,
>> +				    phy_interface_t phy_if)
>> +{
> 
> ...
> 
>> +	if (phy_if == PHY_INTERFACE_MODE_RGMII_ID ||
>> +	    phy_if == PHY_INTERFACE_MODE_RGMII_TXID)
>> +		rgmii_tx_id |= ICSSG_CTRL_RGMII_ID_MODE;
>> +
>> +	regmap_update_bits(ctrl_mmr, icssgctrl_reg, ICSSG_CTRL_RGMII_ID_MODE, rgmii_tx_id);
> 
> Here you are adding the TX delay if the phy-mode indicates it should
> be added.
> 
>> +static int prueth_netdev_init(struct prueth *prueth,
>> +			      struct device_node *eth_node)
>> +{
> 
>> +	ret = of_get_phy_mode(eth_node, &emac->phy_if);
>> +	if (ret) {
>> +		dev_err(prueth->dev, "could not get phy-mode property\n");
>> +		goto free;
>> +	}
> 
>> +	ret = prueth_config_rgmiidelay(prueth, eth_node, emac->phy_if);
>> +	if (ret)
>> +		goto free;
>> +
> 
> Reading it from DT and calling the delay function.
> 
>> +static int prueth_probe(struct platform_device *pdev)
>> +{
> 
> 
>> +	/* register the network devices */
>> +	if (eth0_node) {
>> +		ret = register_netdev(prueth->emac[PRUETH_MAC0]->ndev);
>> +		if (ret) {
>> +			dev_err(dev, "can't register netdev for port MII0");
>> +			goto netdev_exit;
>> +		}
>> +
>> +		prueth->registered_netdevs[PRUETH_MAC0] = prueth->emac[PRUETH_MAC0]->ndev;
>> +
>> +		emac_phy_connect(prueth->emac[PRUETH_MAC0]);
> 
> And this is connecting the MAC and the PHY, where emac_phy_connect()
> passes emac->phy_if to phylib.
> 
> What i don't see anywhere is you changing emac->phy_if to indicate the
> MAC has inserted the TX delay, and so the PHY should not.
> 

Yes, there is no indication whether MAC has enabled TX delay or not. I have
changed the phy-mode in DT from "rgmii-rxid" to "rgmii-id" as per your
suggestion in previous revision. I will keep Tx Internal delay as it is(getting
configured in MAC) and inside emac_phy_connect() API, while calling
of_phy_connect() instead of passing emac->phy_if (which is rgmii-id as per DT),
I will pass PHY_INTERFACE_MODE_RGMII_RXID. This will make sure that phy only
enables Rx delay and keep the existing approach of keepping Tx delay in MAC.

Currently, in emac_phy_connect() API,

	/* connect PHY */
	ndev->phydev = of_phy_connect(emac->ndev, emac->phy_node,
				      &emac_adjust_link, 0,
				      emac->phy_if);
I will change it to,

	/* connect PHY */
	ndev->phydev = of_phy_connect(emac->ndev, emac->phy_node,
				      &emac_adjust_link, 0,
				      PHY_INTERFACE_MODE_RGMII_RXID);

Let me know if this looks OK.

>     Andrew
> 

-- 
Thanks and Regards,
Danish.