Re: Call for stge(4) testers

> On Sat, Jul 08, 2006 at 09:24:23PM -0700, Matthew Jacob wrote:
>  > Jason THorpe did one for NetBSD.
>  > 
>  > I did one for Solaris. Nice chip. Too bad it wasn't more popular.
>  > 
> 
> I'm satisfied with the performance and easy interface for the chip.
> But the lack of Tx interrupt moderation and extra accesses to a
> status register to check which kind of Tx errors were occurred are
> serious fault. Since the the error condition uses the same status
> bit in interrupt status register it's hard to distingush failures
> from sucess without extra register accesses.
> 
> BTW, I still have no clue how jumbo frame work on this chip. The
> documentation from wpaul didn't say any special things regarding
> jumbo frame. For instance the doc. said it supports jumbo frame
> up to 9022 but it seems the NIC can work with larger size.
> Even windows driver has a larger size than this, so I'm curious
> important part for jumbo frame were not released?

You have failed to specify in what way jumbo frame support doesn't work.
In your previous mail, you only said there was a "jumbo frame problem"
but did not elaborate further. What exactly _is_ the problem? Does it
not transmit jumbo frames correctly? Does it not receive them correctly?
Does C'thulu emerge from inside the machine and devour your soul?
(If so, this is a sure sign you left the 'devour soul' bit in the
control register turned on. I *hate* it when that happens.)

The documentation refers to a 'MaxFrameSize' register (offset 0x86,
16 bits access) which controls the point at which the receiver will
consider an inbound frame to be a giant. The default is 0x5ea (1514
bytes). I think you'll need to increase this to 9014 to receive 9K
jumbo frames (or 9018 for VLAN-tagged jumbo frames). It looks like
the register maxes out at 0x3FFF (16K), which is probably why the
Windows driver claimes to support frames larger than 9K. Note that
for this to work, you'll have to set up the RX descriptors with
enough buffer space to hold 9K of packet data. I haven't looked at
the driver code, but you should be able to set up the fragment array
in each RX descriptor to hold 5 mbufs with 2K clusters. You'll be
wasting a bit of space, but not necessarily as much as if you were
to allocate a single 9K buffer per descriptor.

I don't see anything that limits TX frame size, though you might want
to look around and see if there's a TX threshold setting and try to
increase it if you see underruns.

You need to establish a proper test setup to diagnose the problem. Plug
the NIC directly into another known good gigE card that does jumbo frames,
use ifconfig to set the MTU on both ports to 9000, monitor both sides of
the link with tcpdump/ethereal/whatever, then do "ping -s 8192 <dest IP>"
from both ends and see what happens.

-Bill

--
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-Bill Paul            (510) 749-2329 | Senior Engineer, Master of Unix-Fu
                 wpaul_at_windriver.com | Wind River Systems
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              <adamw> you're just BEGGING to face the moose
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