Re: [PATCH net-next v3 0/3] Initial support for PIC64-HPSC/HX Ethernet endpoint

[Charles Perry <charles.perry@microchip.com>]

On Mon, Mar 16, 2026 at 06:28:39PM +0100, Théo Lebrun wrote:
> Hello Charles,
> 
> On Fri Mar 13, 2026 at 3:06 PM CET, Charles Perry wrote:
> > Hello,
> >
> > This series add basic support for Microchip "PIC64-HPSC" and "PIC64HX"
> > Ethernet endpoint. Both SoCs contain 4 GEM IP with support for
> > MII/RGMII/SGMII/USXGMII at rates of 10M to 10G. Only RGMII and SGMII at a
> > rate of 1G is tested for now. Each GEM IP has 8 priority queues and the
> > revision register reads 0x220c010e.
> 
> Do you have plans to test higher rate? We might get our hands on GEMs
> that support >1G and would like to know if CCing you would make sense.

Yes. I don't have a 10G setup right now but that's definitively in my TODO
list for this year.

> 
> > One particularity of this instantiation of GEM is that the MDIO controller
> > within the GEM IP is disconnected from any physical pin and the SoC rely on
> > another standalone MDIO controller.
> 
> Ah, that means you instantiate the MDIO bus for no good reason.
> Code looks like:
> 
> static int macb_mii_init(struct macb *bp)
> {
> 	struct device_node *mdio_np, *np = bp->pdev->dev.of_node;
> 	int err = -ENXIO;
> 
> 	/* With fixed-link, we don't need to register the MDIO bus,
> 	 * except if we have a child named "mdio" in the device tree.
> 	 * In that case, some devices may be attached to the MACB's MDIO bus.
> 	 */
> 	mdio_np = of_get_child_by_name(np, "mdio");
> 	if (!mdio_np && of_phy_is_fixed_link(np))
> 		return macb_mii_probe(bp->dev);
> 
> 	// ... probe MDIO bus ...
> }
> 
> So to *not* get the bus we need to be in fixed link config. Do you care
> about that? I think that the proper fix would be to lazy probe the MDIO
> bus until a PHY (ours or some other MAC's) asks for it.

Yes, I do have a bunch of unusable MDIO buses in sysfs. It would be great
if those just didn't exist but that would be yet more code and one more
MACB_CAPS for little benefit IMO.

As for the fixed link, I can't specify that just to not instantiate the
MDIO bus because that would cause other problems since my link has a PHY
with a negotiated rate/duplex/etc.

Thanks,
Charles

> 
> Thanks,
> 
> --
> Théo Lebrun, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>