linux-kernel - Re: [PATCH v3 3/5] net: phy: qcom: at803x: Add Qualcomm IPQ5018 Internal PHY support

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Message-ID:
 <DS7PR19MB8883B6501250F67CB83415BD9D62A@DS7PR19MB8883.namprd19.prod.outlook.com>
Date: Mon, 2 Jun 2025 17:02:12 +0400
From: George Moussalem <george.moussalem@...look.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
 Russell King <linux@...linux.org.uk>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Florian Fainelli <f.fainelli@...il.com>,
 Philipp Zabel <p.zabel@...gutronix.de>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, netdev@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 linux-clk@...r.kernel.org
Subject: Re: [PATCH v3 3/5] net: phy: qcom: at803x: Add Qualcomm IPQ5018
 Internal PHY support

Hi Andrew,

On 6/2/25 16:41, Andrew Lunn wrote:
>> +	/* PHY DAC values are optional and only set in a PHY to PHY link architecture */
>> +	if (priv->set_short_cable_dac) {
>> +		/* setting MDAC (Multi-level Digital-to-Analog Converter) in MMD1 */
>> +		phy_modify_mmd(phydev, MDIO_MMD_PMAPMD, IPQ5018_PHY_MMD1_MDAC,
>> +			       IPQ5018_PHY_DAC_MASK, IPQ5018_PHY_MMD1_MDAC_VAL);
>> +
>> +		/* setting EDAC (Error-detection and Correction) in debug register */
>> +		at803x_debug_reg_mask(phydev, IPQ5018_PHY_DEBUG_EDAC,
>> +				      IPQ5018_PHY_DAC_MASK, IPQ5018_PHY_DEBUG_EDAC_VAL);
>> +	}
> 
> In the binding you say:
> 
> 
> +            If not set, it is assumed the MDI output pins of this PHY are directly
> +            connected to an RJ45 connector and default DAC values will be used.
> 
> So shouldn't there be an else clause here setting these two values to
> their default, undoing what the bootloader might of done etc.

DAC values are only set if the property is set in the DTS. If the 
property is not set, the default values set by the PHY itself are used, 
and as you mentioned below, DAC values aren't modified by the driver.

> 
> Or you can change the binding, and say something like:
> 
> +            If not set, DAC values are not modified.

sure, anything else you need changed for v4?

> 
> We often need a tristate in DT, set something, unset something, leave
> it as it is. But that does not exist in DT in an easy form :-(

> 
> 	Andrew

Best regards,
George