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Date: Thu, 19 Feb 2009 19:24:07 +0900
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From: Hiroharu Tamaru <tamaru@myn.rcast.u-tokyo.ac.jp>
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Subject: Can ASPM be disabled on 82573 to allow Jumbo Frames with em(4)?
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Hi

I am not sure if I am understanding things right, but is it
possible to forcibly disable ASPM in em(4) for 82573
devices?

What I wanted to do is to use Jumbo Frames for these NICs
and I saw in sys/dev/e1000/if_em.c that says:

| static int
| em_ioctl(struct ifnet *ifp, u_long command, caddr_t data)
| {
(snip)
| 	case SIOCSIFMTU:
(snip)
| 		case e1000_82573:
| 			/*
| 			 * 82573 only supports jumbo frames
| 			 * if ASPM is disabled.
| 			 */
| 			e1000_read_nvm(&adapter->hw,
| 			    NVM_INIT_3GIO_3, 1, &eeprom_data);
| 			if (eeprom_data & NVM_WORD1A_ASPM_MASK) {
| 				max_frame_size = ETHER_MAX_LEN;
| 				break;
| 			}
| 			/* Allow Jumbo frames - fall thru */
| 		case e1000_82571:


I also found that in Linux, they seem to disable ASPM for certain cases:

http://kerneltrap.org/mailarchive/linux-netdev/2007/10/31/374573

So I started to wonder if there is a knob already in FreeBSD
to disable ASPM for 82573 and (as a side effect?) allows one to
use Jumbo Frames with this device, or I such can be introduced easily.

It would be nice to be able to enable Jumbo Frames if the
power consumption is not of a problem..

Thanks.

Hiroharu