netdev - Re: [PATCH net-next v8 08/11] net: stmmac: dwmac-loongson: Fix MAC speed for GNET

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Date: Thu, 21 Mar 2024 17:29:55 +0800
From: Yanteng Si <siyanteng@...ngson.cn>
To: Serge Semin <fancer.lancer@...il.com>
Cc: andrew@...n.ch, hkallweit1@...il.com, peppe.cavallaro@...com,
 alexandre.torgue@...s.st.com, joabreu@...opsys.com, Jose.Abreu@...opsys.com,
 chenhuacai@...ngson.cn, linux@...linux.org.uk, guyinggang@...ngson.cn,
 netdev@...r.kernel.org, chris.chenfeiyang@...il.com
Subject: Re: [PATCH net-next v8 08/11] net: stmmac: dwmac-loongson: Fix MAC
 speed for GNET


在 2024/3/20 01:02, Serge Semin 写道:
>>> Due to a bug in the chip's internal PHY, the network is still not working after
>>> the first self-negotiation, and it needs to be self-negotiated again.
> Then please describe the bug in more details then.
>
> Getting back to the code you implemented here. In the in-situ comment
> you say: "We need to use the PS bit to check if the controller's
> status is correct and reset PHY if necessary." By calling
> phy_restart_aneg() you don't reset the PHY.
>
> Moreover if "PS" flag is set, then the MAC has been pre-configured to
> work in the 10/100Mbps mode. Since 1000Mbps speed is requested, the
> MAC_CTRL_REG.PS flag will be cleared later in the
> stmmac_mac_link_up() method and then phylink_start() shall cause the
> link speed re-auto-negotiation. Why do you need the auto-negotiation
> started for the default MAC config which will be changed just in a
> moment later? All of that seems weird.

When switching speeds (from 100M to 1000M), the phy cannot output clocks,

resulting in the unavailability of the network card.  At this time, a 
reset of the

phy is required.


BTW, This bug has been fixed in gnet of 2k2000 (0x10, 7a13).

>
> Most importantly I have doubts the networking subsystem maintainers
> will permit you calling the phy_restart_aneg() method from the MAC
> driver code.

We are happy to accept the opinions of the community.


Thanks,

Yanteng

>