linux-kernel - Re: [PATCH net-next v2 2/6] net: phy: microchip_t1s: replace read-modify-write code with phy_modify

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Message-ID: <2c78f2cc-ff5e-4dcd-a309-de21a5725053@lunn.ch>
Date:   Mon, 22 May 2023 14:31:24 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Parthiban Veerasooran <Parthiban.Veerasooran@...rochip.com>
Cc:     hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ramon.nordin.rodriguez@...roamp.se, horatiu.vultur@...rochip.com,
        Woojung.Huh@...rochip.com, Nicolas.Ferre@...rochip.com,
        Thorsten.Kummermehr@...rochip.com
Subject: Re: [PATCH net-next v2 2/6] net: phy: microchip_t1s: replace
 read-modify-write code with phy_modify_mmd

>  
>  	/* Read-Modified Write Pseudocode (from AN1699)
>  	 * current_val = read_register(mmd, addr) // Read current register value

Hi Parthiban

Maybe extend the comment to indicate that although AN1699 says Read,
Modify, Write, the write is not required if the register already has
the required value. That is what phy_modify_mmd() actually does.

> @@ -74,12 +72,11 @@ static int lan867x_config_init(struct phy_device *phydev)
>  	 * write_register(mmd, addr, new_val) // Write back updated register value
>  	 */
>  	for (int i = 0; i < ARRAY_SIZE(lan867x_fixup_registers); i++) {
> -		reg = lan867x_fixup_registers[i];
> -		reg_value = phy_read_mmd(phydev, MDIO_MMD_VEND2, reg);
> -		reg_value &= ~lan867x_fixup_masks[i];
> -		reg_value |= lan867x_fixup_values[i];
> -		err = phy_write_mmd(phydev, MDIO_MMD_VEND2, reg, reg_value);
> -		if (err != 0)
> +		err = phy_modify_mmd(phydev, MDIO_MMD_VEND2,
> +				     lan867x_fixup_registers[i],
> +				     lan867x_fixup_masks[i],
> +				     lan867x_fixup_values[i]);
> +		if (err)
>  			return err;
>  	}


    Andrew

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