netdev - Re: [PATCH net-next 2/2] r8169: add support for reading over-temp threshold

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Message-ID: <088501b8-1c55-4d20-95b3-ed635865b470@gmail.com>
Date: Mon, 6 Jan 2025 23:31:35 +0100
From: Heiner Kallweit <hkallweit1@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Realtek linux nic maintainers <nic_swsd@...ltek.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Eric Dumazet <edumazet@...gle.com>, David Miller <davem@...emloft.net>,
 Andrew Lunn <andrew+netdev@...n.ch>, Simon Horman <horms@...nel.org>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 2/2] r8169: add support for reading over-temp
 threshold

On 06.01.2025 22:15, Andrew Lunn wrote:
> On Mon, Jan 06, 2025 at 07:05:13PM +0100, Heiner Kallweit wrote:
>> Add support for reading the over-temp threshold. If the chip temperature
>> exceeds this value, the chip will reduce the speed to 1Gbps (by disabling
>> 2.5G/5G advertisement and triggering a renegotiation).
> 
> I'm assuming here that the over-temp threshold always exists when the
> temp_in sensors exists? If so:
> 
Right

> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> 
> Does it reduce the speed in the same way as downshift? Can the user
> tell it has happened, other than networking is slower?
> 
It internally disables 2.5G/5G advertisement and triggers an autoneg.
So you get the usual message on console/dmesg indicating the new speed.
This internal action sets a register bit, and it can also trigger an interrupt.
So it should be possible to check in the link_change_notify() callback
whether an over-temp event occurred. The silent change of the advertisement
may also result in the phylib-cached advertisement being out-of-sync.
So we would have to re-sync it. But I didn't fully test this yet.

This patch only allows to read the over-temp threshold set as power-on default
or by the boot loader. It doesn't change the existing behavior.

>     Andrew

Heiner