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Subject: Re: [PATCH v4 1/3] net: dsa: microchip: implement KSZ87xx Module 3
 low-loss cable errata
To: Fidelio Lawson <lawson.fidelio@gmail.com>,
 Woojung Huh <woojung.huh@microchip.com>, UNGLinuxDriver@microchip.com,
 Andrew Lunn <andrew@lunn.ch>, Vladimir Oltean <olteanv@gmail.com>,
 "David S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>,
 Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
 Marek Vasut <marex@denx.de>,
 Maxime Chevallier <maxime.chevallier@bootlin.com>,
 Simon Horman <horms@kernel.org>, Heiner Kallweit <hkallweit1@gmail.com>,
 Russell King <linux@armlinux.org.uk>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
 Fidelio Lawson <fidelio.lawson@exotec.com>
References: <20260417-ksz87xx_errata_low_loss_connections-v4-0-6c7044ec4363@exotec.com>
 <20260417-ksz87xx_errata_low_loss_connections-v4-1-6c7044ec4363@exotec.com>
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From: Marek Vasut <marex@nabladev.com>
In-Reply-To: <20260417-ksz87xx_errata_low_loss_connections-v4-1-6c7044ec4363@exotec.com>
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On 4/17/26 2:44 PM, Fidelio Lawson wrote:

[...]

> @@ -1271,6 +1287,29 @@ int ksz8_w_phy(struct ksz_device *dev, u16 phy, u16 reg, u16 val)
>   		if (ret)
>   			return ret;
>   		break;
> +	case PHY_REG_KSZ87XX_SHORT_CABLE:
> +		if (!ksz_is_ksz87xx(dev))
> +			return -EOPNOTSUPP;
> +		ret = ksz87xx_apply_low_loss_preset(dev, !!val);
> +		if (ret)
> +			return ret;
> +		break;
> +	case PHY_REG_KSZ87XX_LPF_BW:
> +		if (!ksz_is_ksz87xx(dev))
> +			return -EOPNOTSUPP;
> +		ret = ksz8_ind_write8(dev, TABLE_LINK_MD, KSZ87XX_REG_PHY_LPF, (u8)val);
> +		if (ret)
> +			return ret;
> +		dev->lpf_bw = val;
> +		break;
> +	case PHY_REG_KSZ87XX_EQ_INIT:
> +		if (!ksz_is_ksz87xx(dev))
> +			return -EOPNOTSUPP;
> +		ret = ksz8_ind_write8(dev, TABLE_LINK_MD, KSZ87XX_REG_DSP_EQ, (u8)val);
Do these values need some check, so they would be in the correct 
range(s) / in the correct bitfields before being written into those 
registers ?