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Date: Fri, 17 Apr 2026 17:22:30 +0200
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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>
 <10e325c0-aeb0-47b1-b758-e4f47ff7b004@nabladev.com>
 <56034c9c-fede-4ede-b68d-5ecc484a64cd@gmail.com>
Content-Language: en-US
From: Marek Vasut <marex@nabladev.com>
In-Reply-To: <56034c9c-fede-4ede-b68d-5ecc484a64cd@gmail.com>
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On 4/17/26 5:20 PM, Fidelio LAWSON wrote:
> On 4/17/26 16:35, Marek Vasut wrote:
>> 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 ?
> 
> Yes, I can add validation to ensure that only the documented bitfields 
> are accepted before writing the registers, (bits [7:6] for the LPF 
> bandwidth and bits [5:0] for the DSP EQ initial value).
Yes please, thank you !