ale(4) cannot negotiate as GigE

Hi there,

I've recently put back online one of my home servers, updated to the latest
-CURRENT code.  All went fine, but one thing bothers me.  This box bears
Asus P5Q Pro mobo, with the following onboard NIC:

ale0_at_pci0:2:0:0:        class=0x020000 card=0x82261043 chip=0x10261969
rev=0xb0 hdr=0x00
    vendor     = 'Atheros Communications Inc.'
    device     = 'AR8121/AR8113/AR8114 Gigabit or Fast Ethernet'
    class      = network
    subclass   = ethernet

According the the specs, it should be GigE.  In fact, when plugged into a
capable switch, it displays "green" (gig) status (same on the switch), but
once being initialized by the kernel, it downgrades to yellowish 100mbps
(real speeds agree).

I'm not sure why it happens; maybe it's somehow related to a handful of
those "ale0: link state changed to DOWN/UP" flip-flops I see in dmesg(8),
before it can finally obtain DHCP lease?

I remember these adapters had problems in the past, like infamous "Corrupted
MAC on input" disconnect messages, but I don't recall that I could not use
it in GigE mode.  Anything I can do about it?  Googling did not help much:
most reports date back to ca. 2009, and apparently were ironed out in later
revisions (e.g. selectively disabling checksum offloading).  Thanks,

./danfe