Re: [EXT] Re: [PATCH RFC net-next 03/19] net: mvpp2: add CM3 SRAM memory map

On Sun, Jan 10, 2021 at 06:09:39PM +0000, Stefan Chulski wrote:

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+	} else {
+		priv->sram_pool = of_gen_pool_get(dn, "cm3-mem", 0);
+		if (!priv->sram_pool) {
+			dev_warn(&pdev->dev, "DT is too old, TX FC

disabled\n");

I don't see anything in this patch that disables TX flow control,
which means this warning message is misleading.

OK, I would change to TX FC not supported.

And you should tell phlylink, so it knows to disable it in autoneg.

Which make me wonder, do we need a fix for stable? Has flow control never
been support in this device up until these patches get merged?
It should not be negotiated if it is not supported, which means telling phylink.

   Andrew

TX FC never were really supported. MAC or PHY can negotiated flow control.
But MAC would never trigger FC frame.

That really sucks.

Should I prepare separate patch that disable TX FC till we merge this patches?

From what I see in table 28B in 802.3, there is no way to advertise
that you only support RX flow control. If you advertise ASM_DIR=1
PAUSE=0, it basically means you support sending FC frames, but not
receiving them. Advertising anything with PAUSE=1 means you support
both sending and receiving FC frames, irrespective of the state of
ASM_DIR.

So, our only option would be to completely disable pause frames.
Yes, I think we need a separate patch for that for the net tree,
and it should be backported to stable kernels, IMHO.

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