linux-kernel - Re: [PATCH v2 2/2] net: phy: dp83826: support TX data voltage tuning

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Date: Wed, 7 Feb 2024 19:35:47 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Catalin Popescu <catalin.popescu@...ca-geosystems.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
	robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, afd@...com, hkallweit1@...il.com,
	linux@...linux.org.uk, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	bsp-development.geo@...ca-geosystems.com, m.felsch@...gutronix.de
Subject: Re: [PATCH v2 2/2] net: phy: dp83826: support TX data voltage tuning

> +static int dp83826_config_init(struct phy_device *phydev)
> +{
> +	struct dp83822_private *dp83822 = phydev->priv;
> +	u16 val, mask;
> +	int ret;
> +
> +	if (dp83822->cfg_dac_minus != DP83826_CFG_DAC_MINUS_DEFAULT) {
> +		val = FIELD_PREP(DP83826_VOD_CFG1_MINUS_MDI_MASK, dp83822->cfg_dac_minus) |
> +		      FIELD_PREP(DP83826_VOD_CFG1_MINUS_MDIX_MASK,
> +				 FIELD_GET(DP83826_CFG_DAC_MINUS_MDIX_5_TO_4,
> +					   dp83822->cfg_dac_minus));
> +		mask = DP83826_VOD_CFG1_MINUS_MDIX_MASK | DP83826_VOD_CFG1_MINUS_MDI_MASK;
> +		ret = phy_modify_mmd(phydev, DP83822_DEVADDR, MII_DP83826_VOD_CFG1, mask, val);
> +		if (ret)
> +			return ret;
> +
> +		val = FIELD_PREP(DP83826_VOD_CFG2_MINUS_MDIX_MASK,
> +				 FIELD_GET(DP83826_CFG_DAC_MINUS_MDIX_3_TO_0,
> +					   dp83822->cfg_dac_minus));
> +		mask = DP83826_VOD_CFG2_MINUS_MDIX_MASK;
> +		ret = phy_modify_mmd(phydev, DP83822_DEVADDR, MII_DP83826_VOD_CFG2, mask, val);
> +		if (ret)
> +			return ret;
> +	}

I could be reading this wrong, but it looks like
DP83826_CFG_DAC_MINUS_DEFAULT actually means leave the value
unchanged? Is there anything guaranteeing it does in fact have the
default value in the hardware?

	Andrew