netdev - Re: [RFC PATCH net-next 4/4] net: dp83869: Add RGMII internal delay configuration

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Message-ID: <20200523145832.GJ610998@lunn.ch>
Date:   Sat, 23 May 2020 16:58:32 +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: [RFC PATCH net-next 4/4] net: dp83869: Add RGMII internal delay
 configuration

On Thu, May 21, 2020 at 12:48:34PM -0500, Dan Murphy wrote:
> Add RGMII internal delay configuration for Rx and Tx.
> 
> Signed-off-by: Dan Murphy <dmurphy@...com>
> ---
>  drivers/net/phy/dp83869.c | 101 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 101 insertions(+)
> 
> diff --git a/drivers/net/phy/dp83869.c b/drivers/net/phy/dp83869.c
> index cfb22a21a2e6..40c34fefffe4 100644
> --- a/drivers/net/phy/dp83869.c
> +++ b/drivers/net/phy/dp83869.c
> @@ -99,6 +99,14 @@
>  #define DP83869_OP_MODE_MII			BIT(5)
>  #define DP83869_SGMII_RGMII_BRIDGE		BIT(6)
>  
> +/* RGMIIDCTL bits */
> +#define DP83869_RGMII_TX_CLK_DELAY_SHIFT	4
> +#define DP83869_RGMII_CLK_DELAY_INV		0
> +
> +static int dp83869_internal_delay[] = {250, 500, 750, 1000, 1250, 1500, 1750,
> +				       2000, 2250, 2500, 2750, 3000, 3250,
> +				       3500, 3750, 4000};
> +
>  enum {
>  	DP83869_PORT_MIRRORING_KEEP,
>  	DP83869_PORT_MIRRORING_EN,
> @@ -108,6 +116,8 @@ enum {
>  struct dp83869_private {
>  	int tx_fifo_depth;
>  	int rx_fifo_depth;
> +	u32 rx_id_delay;
> +	u32 tx_id_delay;
>  	int io_impedance;
>  	int port_mirroring;
>  	bool rxctrl_strap_quirk;
> @@ -182,6 +192,7 @@ static int dp83869_of_init(struct phy_device *phydev)
>  	struct dp83869_private *dp83869 = phydev->priv;
>  	struct device *dev = &phydev->mdio.dev;
>  	struct device_node *of_node = dev->of_node;
> +	int delay_size = ARRAY_SIZE(dp83869_internal_delay);
>  	int ret;
>  
>  	if (!of_node)
> @@ -232,6 +243,26 @@ static int dp83869_of_init(struct phy_device *phydev)
>  				 &dp83869->tx_fifo_depth))
>  		dp83869->tx_fifo_depth = DP83869_PHYCR_FIFO_DEPTH_4_B_NIB;
>  
> +	dp83869->rx_id_delay = DP83869_RGMII_CLK_DELAY_INV;
> +	ret = of_property_read_u32(of_node, "rx-internal-delay",
> +				   &dp83869->rx_id_delay);
> +	if (!ret && dp83869->rx_id_delay > dp83869_internal_delay[delay_size]) {
> +		phydev_err(phydev,
> +			   "rx-internal-delay value of %u out of range\n",
> +			   dp83869->rx_id_delay);
> +		return -EINVAL;
> +	}

Hi Dan

Seems like the helper should be doing the range check, and printing
the message. It should be common to all PHY drivers using delays
looked up in a list.

I also wonder about putting the of_property_read_u32 inside a
helper. Something like

of_get_phy_rgmii_delays(struct device_node *np, phy_interface_t interface,
			u32 *rx_delay, u32 *tx_delay)

And maybe a third helper which combines phy_get_delay_index() and
of_get_phy_rgmii_delays().

> +static int dp83869_verify_rgmii_cfg(struct phy_device *phydev)
> +{
> +	struct dp83869_private *dp83869 = phydev->priv;
> +
> +	/* RX delay *must* be specified if internal delay of RX is used. */

No. As i said last time, default to 2ns, if there is no specific delay
value in DT.

    Andrew