Re: [PATCH net-next 2/2] net: stmmac: dwmac4: Use the full perfect filter ability for UC filter

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi,

On 9/1/26 02:12, Andrew Lunn wrote:
> On Mon, Aug 31, 2026 at 09:01:20AM +0200, Maxime Chevallier wrote:
>> Contrary to dwmac1000 that gets its number of perfect filter entries
>> through the 'snps,perfect-filter-entries' property, dwmac4 allows
>> reading the filter size from the HW features registers.
> 
> Does dwmac4 take any notice of "snps,perfect-filter-entries"? Should
> it be marked deprecated?

It's only used on :

  "st,spear600-gmac"
  "snps,dwmac-3.50a"
  "snps,dwmac-3.70a"
  "snps,dwmac-3.72a"
  "snps,dwmac"

So, dwmac1000.

I'd say, we can definitely deprecate on IPs that don't match these.

Interestingly, there are _some_ dwmac4 devicetrees out there that use
this property. It achieves nothing, and even worse, doesn't match what
the HW reports :

In arch/riscv/boot/dts/starfive/jh7110.dtsi for example :

gmac1: ethernet@16040000 {                                            
	compatible = "starfive,jh7110-dwmac", "snps,dwmac-5.20";
	[...]
	snps,perfect-filter-entries = <256>;
}

To my knowledge, 256 isn't even possible, there's only 128 MAC address
registers available :/

perfect filter size discovery on real HW says there's on 8 available,
I haven't measured the actual size of the filter though but it seems
more plausible than 256.

Maxime