linux-kernel - Re: [PATCH net v5 0/4] net: phy: bcm54811: Fix the PHY initialization

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Message-ID: <b89e3a66-3c98-45b3-9f16-8247ac1dc1f4@axis.com>
Date: Thu, 3 Jul 2025 11:03:19 +0200
From: Kamil Horák (2N) <kamilh@...s.com>
To: Florian Fainelli <florian.fainelli@...adcom.com>,
 Jakub Kicinski <kuba@...nel.org>
Cc: bcm-kernel-feedback-list@...adcom.com, andrew@...n.ch,
 hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
 edumazet@...gle.com, pabeni@...hat.com, krzk+dt@...nel.org,
 conor+dt@...nel.org, netdev@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, robh@...nel.org, andrew+netdev@...n.ch,
 horms@...nel.org, corbet@....net, linux-doc@...r.kernel.org
Subject: Re: [PATCH net v5 0/4] net: phy: bcm54811: Fix the PHY initialization



On 7/3/25 01:46, Florian Fainelli wrote:
> On 7/2/25 15:02, Jakub Kicinski wrote:
>> On Tue, 1 Jul 2025 09:50:11 +0200 Kamil Horák - 2N wrote:
>>> PATCH 1 - Add MII-Lite PHY interface mode as defined by Broadcom for
>>>     their two-wire PHYs. It can be used with most Ethernet controllers
>>>     under certain limitations (no half-duplex link modes etc.).
>>>
>>> PATCH 2 - Add MII-Lite PHY interface type
>>>
>>> PATCH 3 - Activation of MII-Lite interface mode on Broadcom bcm5481x
>>>     PHYs
>>>
>>> PATCH 4 - Fix the BCM54811 PHY initialization so that it conforms
>>>     to the datasheet regarding a reserved bit in the LRE Control
>>>     register, which must be written to zero after every device reset.
>>>     Also fix the LRE Status register reading, there is another bit to
>>>     be ignored on bcm54811.
>>
>> I'm a bit lost why the first 3 patches are included in a series for net.
>> My naive reading is we didn't support this extra mode, now we do,
>> which sounds like a new feature.. Patch 4, sure, but the dependency
>> is not obvious.
> 
> I don't see the dependency either, at least not in an explicit way. 
> Kamil, could patch #4 stand on its own and routed through "net" while 
> patches 1-3 are routed through "net-next"?
It can be done this way, however, even the patch #3 is effectively a 
fix, not new feature, because the bcm54811 PHY in MLP package only has 
MII-Lite interface available externally. As far I know, there is no BGA 
casing available for bcm54811 (unlike bcm54810, that one having both MLP 
and BGA). Thus, it cannot function without being switched to MII-Lite 
mode. The introduction of MII-Lite itself is clearly a new feature and 
it is even (theoretically) available for any MII-capable PHY. So if 
putting it all to net it is really impossible or contrary to the 
net-next vs. net selection rules, let's divide it....
To get fully functional, bcm54811-based networking, all patches are 
necessary so any other user out there must wait for both branches to join.

> 
> Thanks


Kamil