Re: genphy_read_status() vs. 1000bT Pause capability

On Mon, 2017-03-27 at 21:14 -0700, Florian Fainelli wrote:

quoted

Doesn't fix my other problem with Pause in 1000bT land. Do you know if
that way of reflecting the pause capability by hijacking the old
LPA bits is widely implemented enough that we should put it in
genphy_read_status() ?

Not sure I follow you here? The link partner pause capability is
reflected in phydev->pause and phydev->asym_pause (yes, these are
terrible names) when the link is established. 

Right. The problem is that they aren't for some gigabit links :-)

Basically, in my setup with a PHY which uses genphy_read_status()
(like most of them), I never get those advertised despite the fact
that, I *think* they are supported by the other end (even after fixing
my side of the advertising).

I added a printk inside genphy_read_status() to inspect the result
of the negociation, and this is what I read:

lpa=c1e1 lpagb=3800 adv=de1 common_adv=1e1 common_adv_gb=800

As you can see, LPA doesn't have the Pause bits. *However* it does
have bit 0x80 which can mean ADVERTISE_100HALF, but according to
our own mii.h can also mean ADVERTISE_1000XPAUSE. Similarily it 
has bit 0x100 which can mean ADVERTISE_100FULL but also can mean
ADVERTISE_1000XPSE_ASYM.

In fact we appear to have two functions to interpret them as
such inn the non-uapi mii.h:

	ethtool_adv_to_mii_adv_x
	mii_adv_to_ethtool_adv_x

However they aren't used much in the tree and not at all by the
"genphy" code.

So my question is... when we observe that we have a 1000 link
established, should we use these to "interpret" the LPA bits as
above ?

As it is, we never seem to advertise the capability because we never
decode the above (tried with 2 different PHYs, a Realtek and a
Broadcom) while my Cisco switches, I think, do support Pause.

Hence my question ... how "standard" is the re-use of the LPA bits
for these alternate meanings in 1000bT and should we update genphy
to perform that decoding ?

(I'm trying to download the 802.3 document referenced in the phy.txt
to see if it says anything about it but it's taking forever for some
reason).

Cheers,
Ben.