Re: [PATCH net-next 08/12] net: pse-pd: pd692x0: Add support for PSE PI priority feature

On Tue, 8 Oct 2024 15:57:22 +0200
Oleksij Rempel [off-list ref] wrote:

On Thu, Oct 03, 2024 at 01:41:02AM +0200, Andrew Lunn wrote:

quoted

quoted

+	msg = pd692x0_msg_template_list[PD692X0_MSG_SET_PORT_PARAM];
+	msg.sub[2] = id;
+	/* Controller priority from 1 to 3 */
+	msg.data[4] = prio + 1;  

Does 0 have a meaning? It just seems an odd design if it does not.  

0 is not documented. But there are sub-priority which are not directly
configured by user, but affect the system behavior.

Priority#: Critical – 1; high – 2; low – 3
 For ports with the same priority, the PoE Controller sets the
 sub-priority according to the logic port number. (Lower number gets
 higher priority).

Port priority affects:
1. Power-up order: After a reset, the ports are powered up according to
 their priority, highest to lowest, highest priority will power up first.
2. Shutdown order: When exceeding the power budget, lowest priority
 ports will turn off first.

Should we return sub priorities on the prio get request?

If i see it correctly, even if user do not actively configures priorities,
they are always present. For example port 0 will have always a Prio
higher than Port 10.

We could add a subprio ehtool attribute, but it won't be configurable.
In fact it could be configurable by changing the port matrix order but it is not
a good idea. Applying a new port matrix turn off all the ports.

I am not sure if it is specific to Microchip controller or if it is generic
enough to add the attribute.
I would say not to return it for now.

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com