netdev - Re: [PATCH net-next v4 2/2] phy: mscc: Add support for RGMII delay configuration

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Date: Wed, 24 May 2023 13:09:24 +0300
From: Vladimir Oltean <vladimir.oltean@....com>
To: Harini Katakam <harini.katakam@....com>
Cc: andrew@...n.ch, hkallweit1@...il.com, linux@...linux.org.uk,
	davem@...emloft.net, kuba@...nel.org, edumazet@...gle.com,
	pabeni@...hat.com, wsa+renesas@...g-engineering.com,
	simon.horman@...igine.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, harinikatakamlinux@...il.com,
	michal.simek@....com, radhey.shyam.pandey@....com
Subject: Re: [PATCH net-next v4 2/2] phy: mscc: Add support for RGMII delay
 configuration

On Mon, May 22, 2023 at 05:58:29PM +0530, Harini Katakam wrote:
> diff --git a/drivers/net/phy/mscc/mscc_main.c b/drivers/net/phy/mscc/mscc_main.c
> index 91010524e03d..9e856231e464 100644
> --- a/drivers/net/phy/mscc/mscc_main.c
> +++ b/drivers/net/phy/mscc/mscc_main.c
> @@ -525,17 +525,14 @@ static int vsc85xx_rgmii_set_skews(struct phy_device *phydev, u32 rgmii_cntl,
>  {
>  	u16 rgmii_rx_delay_pos = ffs(rgmii_rx_delay_mask) - 1;
>  	u16 rgmii_tx_delay_pos = ffs(rgmii_tx_delay_mask) - 1;
> +	struct vsc8531_private *vsc8531 = phydev->priv;
>  	u16 reg_val = 0;
>  	int rc;
>  
>  	mutex_lock(&phydev->lock);
>  
> -	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID ||
> -	    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID)
> -		reg_val |= RGMII_CLK_DELAY_2_0_NS << rgmii_rx_delay_pos;
> -	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID ||
> -	    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID)
> -		reg_val |= RGMII_CLK_DELAY_2_0_NS << rgmii_tx_delay_pos;
> +	reg_val |= vsc8531->rx_delay << rgmii_rx_delay_pos;
> +	reg_val |= vsc8531->tx_delay << rgmii_tx_delay_pos;

What about vsc8584_config_init() -> vsc85xx_rgmii_set_skews()? Who will
have configured rx_delay and tx_delay for that call path?

Isn't it better to absorb the device tree parsing logic into
vsc85xx_rgmii_set_skews(), I wonder?

And if we do that, is it still necessary to use struct vsc8531_private
as temporary storage space from vsc85xx_config_init() to vsc85xx_rgmii_set_skews(),
or will two local variables (rx_delay, tx_delay) serve that purpose just fine?

>  
>  	rc = phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_2,
>  			      rgmii_cntl,
> @@ -1808,10 +1805,34 @@ static irqreturn_t vsc8584_handle_interrupt(struct phy_device *phydev)
>  	return IRQ_HANDLED;
>  }
>  
> +static const int vsc8531_internal_delay[] = {200, 800, 1100, 1700, 2000, 2300,
> +					     2600, 3400};

Could you please avoid intermingling this with the function code, and
move it at the top of mscc_main.c?

Also, vsc8531_internal_delay[] or vsc85xx_internal_delay[]? The values
are also good for VSC8572, the other caller of vsc85xx_rgmii_set_skews().

>  static int vsc85xx_config_init(struct phy_device *phydev)
>  {
> -	int rc, i, phy_id;
> +	int delay_size = ARRAY_SIZE(vsc8531_internal_delay);
>  	struct vsc8531_private *vsc8531 = phydev->priv;
> +	struct device *dev = &phydev->mdio.dev;
> +	int rc, i, phy_id;
> +
> +	vsc8531->rx_delay = phy_get_internal_delay(phydev, dev, &vsc8531_internal_delay[0],

You can just write "x" rather than "&x[0]".

> +						   delay_size, true);
> +	if (vsc8531->rx_delay < 0) {
> +		if (phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID ||
> +		    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID)
> +			vsc8531->rx_delay = RGMII_CLK_DELAY_2_0_NS;
> +		else
> +			vsc8531->rx_delay = RGMII_CLK_DELAY_0_2_NS;
> +	}
> +
> +	vsc8531->tx_delay = phy_get_internal_delay(phydev, dev, &vsc8531_internal_delay[0],
> +						   delay_size, false);
> +	if (vsc8531->tx_delay < 0) {
> +		if (phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID ||
> +		    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID)
> +			vsc8531->rx_delay = RGMII_CLK_DELAY_2_0_NS;
> +		else
> +			vsc8531->rx_delay = RGMII_CLK_DELAY_0_2_NS;
> +	}
>  
>  	rc = vsc85xx_default_config(phydev);
>  	if (rc)
> -- 
> 2.17.1
>