[PATCH 6/6] net/phy: Expose 100base-T capability only

[Cyril Bur]

On Fri, 06 May 2016 11:00:02 +1000
Benjamin Herrenschmidt <benh at au1.ibm.com> wrote:

> On Thu, 2016-05-05 at 22:55 +0930, Joel Stanley wrote:
> > On Thu, May 5, 2016 at 10:57 AM, Cyril Bur <cyrilbur at gmail.com>
> > wrote:  
> > > 
> > > From: Gavin Shan <gwshan at linux.vnet.ibm.com>
> > > 
> > > I don't know the specific PHY model deployed on Firestone BMC, but
> > > currently used one (PHY_ID_BCM54210E) isn't correct. BCM54210E
> > > supports 1000base-T but the PHY on Firestone BMC shouldn't support
> > > that mode as uboot uses 100base-T mode.
> > > 
> > > When exposing 1000base-T capability, the MAC is forced to have the
> > > same mode though the PHY is working in 100base-T mode in fact. It
> > > causes the mode mismatch between PHY/MAC and the ethernet network
> > > doesn't work.
> > > 
> > > It's a temporary fix. After the PHY model is confirmed, we need
> > > to enable the correct PHY driver instead current one for BCM54210E.
> > > 
> > > Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
> > > 
> > > [Cyril]
> > > The plot thickens, it does appear that this IS the correct PHY on
> > > firestones. This patch is definitely required for networking to be
> > > functional though.  
> > We should get someone in Austin to boot a firestone without this
> > patch
> > and see what it does. You shouldn't need a pdu as long as you get it
> > right the first time :)  
> 
> The MAC in the ast2400 is a gigabit MAC. So it should all work normally
> at 1000bT. If not, then something is wrong that needs to be
> investigated:
> 
> 	- Either the interface between MAC and PHY isn't wired
> correctly (RGMII vs. RMII, RGMII uses more pins and a diff. clock)
> 
> 	- Or we don't set a setting or strap somewhere to switch
> between those modes (hardware strapping bit[7:6], SCU[A0], ...)
> 
> 	- Both ?
> 

This is something I'm trying to confirm. The firestones I and Gavin have access
to appear to be prerelease, so anythings possible.

I am struggling to get access to a release firestone, when I do I'll check if
Gavins patch is necessary there. If so, then we'll have to start asking those
sorts of questions.

> If we are indeed limited to 100bT, then we should expose that one way
> or another in the device-tree in order to limit the advertized speed in
> the PHY driver.
> 

That is probably going to be the way to go if it turns out there's this issue
on all firestones.


Thanks,

Cyril

> Cheers,
> Ben.
>