netdev - Re: [PATCH net-next v2 3/3] phy: mscc: Add support for VSC8531

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Date:   Wed, 26 Apr 2023 14:18:09 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Harini Katakam <harini.katakam@....com>
Cc:     robh+dt@...nel.org, 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,
        krzysztof.kozlowski+dt@...aro.org, simon.horman@...igine.com,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, harinikatakamlinux@...il.com,
        michal.simek@....com, radhey.shyam.pandey@....com
Subject: Re: [PATCH net-next v2 3/3] phy: mscc: Add support for VSC8531_02
 with RGMII tuning

On Wed, Apr 26, 2023 at 04:13:13PM +0530, Harini Katakam wrote:
> From: Harini Katakam <harini.katakam@...inx.com>
> 
> Add support for VSC8531_02 (Rev 2) device.
> Add support for optional RGMII RX and TX delay tuning via devicetree.
> The hierarchy is:
> - Retain the defaul 0.2ns delay when RGMII tuning is not set.
> - Retain the default 2ns delay when RGMII tuning is set and DT delay
> property is NOT specified.
> - Use the DT delay value when RGMII tuning is set and a DT delay
> property is specified.
> 
> Signed-off-by: Harini Katakam <harini.katakam@....com>
> Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>
> Signed-off-by: Michal Simek <michal.simek@...inx.com>
> ---
> v2:
> - Switch both VSC8531 and VSC8531-02 to use exact phy id match as they
> share the same model number
> - Ensure RCT
> - Improve optional property read
> 
>  drivers/net/phy/mscc/mscc.h      |  3 +++
>  drivers/net/phy/mscc/mscc_main.c | 40 ++++++++++++++++++++++++++++----
>  2 files changed, 39 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/phy/mscc/mscc.h b/drivers/net/phy/mscc/mscc.h
> index a50235fdf7d9..5a26eba0ace0 100644
> --- a/drivers/net/phy/mscc/mscc.h
> +++ b/drivers/net/phy/mscc/mscc.h
> @@ -281,6 +281,7 @@ enum rgmii_clock_delay {
>  #define PHY_ID_VSC8514			  0x00070670
>  #define PHY_ID_VSC8530			  0x00070560
>  #define PHY_ID_VSC8531			  0x00070570
> +#define PHY_ID_VSC8531_02		  0x00070572
>  #define PHY_ID_VSC8540			  0x00070760
>  #define PHY_ID_VSC8541			  0x00070770
>  #define PHY_ID_VSC8552			  0x000704e0
> @@ -373,6 +374,8 @@ struct vsc8531_private {
>  	 * package.
>  	 */
>  	unsigned int base_addr;
> +	u32 rx_delay;
> +	u32 tx_delay;
>  
>  #if IS_ENABLED(CONFIG_MACSEC)
>  	/* MACsec fields:
> diff --git a/drivers/net/phy/mscc/mscc_main.c b/drivers/net/phy/mscc/mscc_main.c
> index 75d9582e5784..80cc90a23d57 100644
> --- a/drivers/net/phy/mscc/mscc_main.c
> +++ b/drivers/net/phy/mscc/mscc_main.c
> @@ -525,6 +525,7 @@ 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;
>  
> @@ -532,10 +533,10 @@ static int vsc85xx_rgmii_set_skews(struct phy_device *phydev, u32 rgmii_cntl,
>  
>  	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;
> +		reg_val |= vsc8531->rx_delay << 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->tx_delay << rgmii_tx_delay_pos;
>  
>  	rc = phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_2,
>  			      rgmii_cntl,
> @@ -1812,6 +1813,15 @@ static int vsc85xx_config_init(struct phy_device *phydev)
>  {
>  	int rc, i, phy_id;
>  	struct vsc8531_private *vsc8531 = phydev->priv;
> +	struct device_node *of_node = phydev->mdio.dev.of_node;
> +
> +	vsc8531->rx_delay = RGMII_CLK_DELAY_2_0_NS;
> +	rc = of_property_read_u32(of_node, "mscc,rx-delay",
> +				  &vsc8531->rx_delay);
> +
> +	vsc8531->tx_delay = RGMII_CLK_DELAY_2_0_NS;
> +	rc = of_property_read_u32(of_node, "mscc,tx-delay",
> +				  &vsc8531->tx_delay);

Since the dt-bindings document says "If this property is present then
the PHY applies the RX|TX delay", then I guess the precedence as applied
by vsc85xx_rgmii_set_skews() should be different. The RX delays should
be applied based on rx-internal-delay-ps (if present) regardless of
phy-mode, or set to RGMII_CLK_DELAY_2_0_NS if we are in the rgmii-rxid
or rgmii-id modes. Similar for tx.

Also, please split the VSC8531-02 addition into a separate patch, since
the configurable RGMII delays also affect existing PHYs (like VSC8502).