linux-kernel - Re: [RFC PATCH 03/11] phy: ti: introduce phy-gmii-sel driver

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Date:   Tue, 9 Oct 2018 02:39:35 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Tony Lindgren <tony@...mide.com>,
        Rob Herring <robh+dt@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Sekhar Nori <nsekhar@...com>, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [RFC PATCH 03/11] phy: ti: introduce phy-gmii-sel driver

On Mon, Oct 08, 2018 at 06:49:41PM -0500, Grygorii Strashko wrote:
> +static int phy_gmii_sel_mode(struct phy *phy, phy_interface_t intf_mode)
> +{
> +	struct phy_gmii_sel_phy_priv *if_phy = phy_get_drvdata(phy);
> +	const struct phy_gmii_sel_soc_data *soc_data = if_phy->priv->soc_data;
> +	struct device *dev = if_phy->priv->dev;
> +	struct regmap_field *regfield;
> +	int ret, rgmii_id = 0;
> +	u32 mode = 0;
> +
> +	if_phy->phy_if_mode = intf_mode;
> +
> +	switch (if_phy->phy_if_mode) {
> +	case PHY_INTERFACE_MODE_RMII:
> +		mode = AM33XX_GMII_SEL_MODE_RMII;
> +		break;
> +
> +	case PHY_INTERFACE_MODE_RGMII:
> +		mode = AM33XX_GMII_SEL_MODE_RGMII;
> +		break;
> +
> +	case PHY_INTERFACE_MODE_RGMII_ID:
> +	case PHY_INTERFACE_MODE_RGMII_RXID:
> +	case PHY_INTERFACE_MODE_RGMII_TXID:
> +		mode = AM33XX_GMII_SEL_MODE_RGMII;
> +		rgmii_id = 1;
> +		break;

Hi Grygorii

It looks like the MAC can do AM33XX_GMII_SEL_MODE_RGMII and
AM33XX_GMII_SEL_MODE_RGMII_ID. I don't think it can do
AM33XX_GMII_SEL_MODE_RGMII_RXID or AM33XX_GMII_SEL_MODE_RGMII_TXID?  I
would prefer it return -EINVAL when asked to do something it cannot
do.

> +
> +	default:
> +		dev_warn(dev,
> +			 "port%u: unsupported mode: \"%s\". Defaulting to MII.\n",
> +			 if_phy->id, phy_modes(rgmii_id));
> +		/* fall through */

Returning -EINVAL would be better. Otherwise the DT might never get
fixed.

> +	case PHY_INTERFACE_MODE_MII:
> +		mode = AM33XX_GMII_SEL_MODE_MII;
> +		break;
> +	};
> +
> +	dev_dbg(dev, "%s id:%u mode:%u rgmii_id:%d rmii_clk_ext:%d\n",
> +		__func__, if_phy->id, mode, rgmii_id,
> +		if_phy->rmii_clock_external);
> +
> +	regfield = if_phy->fields[PHY_GMII_SEL_PORT_MODE];
> +	ret = regmap_field_write(regfield, mode);
> +
> +	if (soc_data->features & BIT(PHY_GMII_SEL_RGMII_ID_MODE) &&
> +	    if_phy->fields[PHY_GMII_SEL_RGMII_ID_MODE]) {
> +		regfield = if_phy->fields[PHY_GMII_SEL_RGMII_ID_MODE];
> +		ret |= regmap_field_write(regfield, rgmii_id);
> +	}
> +
> +	if (soc_data->features & BIT(PHY_GMII_SEL_RMII_IO_CLK_EN) &&
> +	    if_phy->fields[PHY_GMII_SEL_RMII_IO_CLK_EN]) {
> +		regfield = if_phy->fields[PHY_GMII_SEL_RMII_IO_CLK_EN];
> +		ret |= regmap_field_write(regfield,
> +					  if_phy->rmii_clock_external);
> +	}
> +
> +	if (ret) {
> +		dev_err(dev, "port%u: set mode fail %d", if_phy->id, ret);
> +		return -EIO;
> +	}

I would prefer each write had its own error check. The fact you don't
return ret means you know ret could be -EINVAL|-EOIO, making
-EMORECOFFEE.

	Andrew