netdev - Re: LAN8720: RX errors / packet loss when using smsc PHY driver on i.MX6Q

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Message-ID: <7082e2d0-a5a9-4b00-950f-dc513975af1c@gmail.com>
Date: Sat, 15 Nov 2025 22:26:35 +0100
From: Heiner Kallweit <hkallweit1@...il.com>
To: Fabio Estevam <festevam@...il.com>
Cc: Russell King - ARM Linux <linux@...linux.org.uk>,
 edumazet <edumazet@...gle.com>, netdev <netdev@...r.kernel.org>,
 Andrew Lunn <andrew@...n.ch>
Subject: Re: LAN8720: RX errors / packet loss when using smsc PHY driver on
 i.MX6Q

On 11/15/2025 10:01 PM, Fabio Estevam wrote:
> Hi Heiner,
> 
> On Fri, Nov 14, 2025 at 6:33 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
> 
>> The smsc PHY driver for LAN8720 has a number of callbacks and flags.
>> Try commenting them out one after the other until it works.
>>
>> .read_status    = lan87xx_read_status,
>> .config_init    = smsc_phy_config_init,
>> .soft_reset     = smsc_phy_reset,
>> .config_aneg    = lan95xx_config_aneg_ext,
>> .suspend        = genphy_suspend,
>> .resume         = genphy_resume,
>> .flags          = PHY_RST_AFTER_CLK_EN,
>>
>> All of them are optional. If all are commented out, you should have
>> the behavior of the genphy driver.
>>
>> Once we know which callback is problematic, we have a starting point.
> 
> Thanks for the suggestion.
> 
> After removing the '.soft_reset = smsc_phy_reset,' line, there is no
> packet loss anymore.
> 
> If you have any other suggestions regarding smsc_phy_reset(), please
> let me know.
> 
smsc_phy_reset() does two things:
1. set PHY to "all capable" mode if in power-down
2. genphy_soft_reset()

Again, as the genphy driver works fine for you, both parts should be optional.
Check with part is causing the packet loss.

> Thanks