[U-Boot] [PATCH] drivers: net: phy: atheros: apply the previous register setting for AR8031 to fix the voltage peak issue

[Sekhar Nori]

On Friday 03 February 2017 02:53 AM, ken <Ken Lin> wrote:
> Apply the previous setting for the reserved bits in SetDes Test and System Mode Control register
> to avoid the voltage peak issue while we do the IEEE PHY comformance test
> 
> Signed-off-by: ken Lin <ken.lin at advantech.com>
> Tested on Advantech DMS-BA16 board
> Tested-by: Ken Lin <ken.lin at advantech.com>
> ---
>  drivers/net/phy/atheros.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/phy/atheros.c b/drivers/net/phy/atheros.c
> index b34cdd3d87..82fe228604 100644
> --- a/drivers/net/phy/atheros.c
> +++ b/drivers/net/phy/atheros.c
> @@ -28,6 +28,8 @@ static int ar8021_config(struct phy_device *phydev)
>  
>  static int ar8031_config(struct phy_device *phydev)
>  {
> +	int regval;
> +
>  	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID ||
>  	    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID) {
>  		phy_write(phydev, MDIO_DEVAD_NONE, AR803x_PHY_DEBUG_ADDR_REG,
> @@ -44,6 +46,10 @@ static int ar8031_config(struct phy_device *phydev)
>  			  AR803x_RGMII_RX_CLK_DLY);
>  	}
>  
> +        phy_write(phydev, MDIO_DEVAD_NONE, AR803x_PHY_DEBUG_ADDR_REG, AR803x_DEBUG_REG_5);
> +        regval = phy_read(phydev, MDIO_DEVAD_NONE, AR803x_PHY_DEBUG_DATA_REG);
> +        phy_write(phydev, MDIO_DEVAD_NONE, AR803x_PHY_DEBUG_DATA_REG, regval | 0x3C47);

I thought I had responded to this, but probably the mail did not go through.

What you have defeats the purpose of reading back the register. The idea of 
reading back was to avoid using any hardcoded reset state of the register.

Also, your patch does nothing to the existing code writing to AR803x_DEBUG_REG_5.
So you have two unneeded writes now. Does the following work for you (not compiled
or tested).

Thanks,
Sekhar

---8<---
diff --git a/drivers/net/phy/atheros.c b/drivers/net/phy/atheros.c
index b34cdd3d87dc..aff9eb3d18c6 100644
--- a/drivers/net/phy/atheros.c
+++ b/drivers/net/phy/atheros.c
@@ -28,12 +28,16 @@ static int ar8021_config(struct phy_device *phydev)
 
 static int ar8031_config(struct phy_device *phydev)
 {
+	int regval;
+
 	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID ||
 	    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID) {
 		phy_write(phydev, MDIO_DEVAD_NONE, AR803x_PHY_DEBUG_ADDR_REG,
 			  AR803x_DEBUG_REG_5);
+		regval = phy_read(phydev, MDIO_DEVAD_NONE,
+				  AR803x_PHY_DEBUG_DATA_REG);
 		phy_write(phydev, MDIO_DEVAD_NONE, AR803x_PHY_DEBUG_DATA_REG,
-			  AR803x_RGMII_TX_CLK_DLY);
+			  regval | AR803x_RGMII_TX_CLK_DLY);
 	}
 
 	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID ||