Re: [PATCH net-next v2 4/4] net: dsa: soce: Add basic support for SoC-e switch IP cores

[Vasilij Strassheim <v.strassheim@linutronix.de>]

On Thu, 2026-09-10 at 17:07 +0200, Andrew Lunn wrote:
> Thanks for this list.
> 
> > ---
> > Global register block at 0x0000 (three registers currently used)
> > 	0x00 Core Version - Major and minor revision number (RO)
> > 	0x04 Licensed Features (RO)
> > 	0x08 Reserved
> > 	0x0C GUI Configuration - Implemented Features 0 (RO)
> > 	0x10 GUI Configuration - Implemented Features 1 (RO)
> 
> GUI? I assume this is not Graphical User Interface, but something
> else?
> 

It actually stands for Graphical User Interface. This refers to
configuration in a graphical IDE, where the bitstream is customised and
synthesized.
"Implemented Features" can be enabled/disabled and configured there by
clicking on the respective checkboxes or options within the graphical
interface.

> > 	Licensed Features Register (RO) (Bits specify if the given
> > 	feature is enabled by license):
> > 	[31:27] - Maximum Number of Ports: These bits specify the maximum
> > 	number of ports licensed
> > 	[26:15] - Reserved
> > 	- ACL: Access Control List (ACL) feature
> > 	- LLDP: LLDP feature
> > 	- IEEE 802.1X
> > 	- IEEE 802.1AX-2008 - Link Aggregation
> > 	- IEEE 802.3br/IEEE 802.1Qbu - Preemption
> > 	- IEC 61158-4-2 - DLR
> > 	- IEC 62439-2 - MRP
> > 	- IGMP Snooping
> > 	- Port mirroring
> > 	- IEEE 802.1s - MSTP
> > 	- IEEE 802.1w - RSTP
> > 	- IEEE 1588 - Transparent Clock
> > 	- Switch mode: managed or unmanaged
> 
> This is probably something which should be tested in the probe
> method. No point loading the driver if it cannot be managed.
> 

"DSA" functionality is already tested and according to the
documentation, this excludes unmanaged variants. Therefore, I wouldn't
add an additional test for this.

> > 	- Secure Chip
> > 	- Time Limitation
> 
> What do these two mean?
> 

Took me some time to find this info. These are license-protection
features. "Security Chip" authenticates the IP license using an external
1-Wire security device, while "Time Limitation" restricts evaluation
licenses to a configured operating period. Neither is relevant to the
driver.

> > 	MDIO - Control
> > 	[26:16] - Bus selection: These bits specify the port number over
> > 	which MDIO operation is performed.
> 
> 10 bits, which allows more MDIO busses than ports!

Actually 11 bits. However, too much. This may be a documentation error,
since the original driver also used only bits 20:16. I will clarify
this and if it's true, somehow address it as part of the MDIO/mux
rework.

> 
> > > I also wounder at the name. Does the data sheet really call it DSA?
> > > 
> > 
> > Yes, there is even a chapter describing Distributed Switch Architecture
> > (DSA) as "a subsystem that was primarily designed to support specific
> > vendor switches using Linux, ..." followed by information about "custom
> > DSA tagging".
> 
> Does the switch support the D in DSA?
> 

Not as far as I understand. The hardware provides custom frame tagging
between the CPU and a single switch. I found no indication that it
supports cascaded switch trees or encodes a target switch identity in
the tag.

> 
Thanks,
Vasilij