git: fbdb8728d327 - stable/15 - igb: Stop writing the legacy TADV register

The branch stable/15 has been updated by kbowling:

URL: https://cgit.FreeBSD.org/src/commit/?id=fbdb8728d327b8f9f3239ce2733bfd31ce13514c

commit fbdb8728d327b8f9f3239ce2733bfd31ce13514c
Author:     Kevin Bowling <kbowling@FreeBSD.org>
AuthorDate: 2026-07-29 04:23:30 +0000
Commit:     Kevin Bowling <kbowling@FreeBSD.org>
CommitDate: 2026-08-06 07:38:27 +0000

    igb: Stop writing the legacy TADV register
    
    TADV is an em-class interrupt delay register and is absent from the
    82575 and later register model. The igb attach path does not expose or
    initialize that control, but transmit initialization still wrote its
    zero valued storage into a reserved queue-window offset.
    
    Apply the same igb_mac_min boundary already used for TIDV and the
    absolute-delay sysctls.
    
    Sponsored by:   BBOX.io
    
    (cherry picked from commit c637d474045a41b1763c17a8b4b7763d4159504f)
---
 sys/dev/e1000/if_em.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/dev/e1000/if_em.c b/sys/dev/e1000/if_em.c
index 37a118a45848..c5e4676f64c7 100644
--- a/sys/dev/e1000/if_em.c
+++ b/sys/dev/e1000/if_em.c
@@ -3763,7 +3763,7 @@ em_initialize_transmit_unit(if_ctx_t ctx)
 			sc->txd_cmd |= E1000_TXD_CMD_IDE;
 	}
 
-	if (hw->mac.type >= e1000_82540)
+	if (hw->mac.type >= e1000_82540 && hw->mac.type < igb_mac_min)
 		E1000_WRITE_REG(hw, E1000_TADV, sc->tx_abs_int_delay.value);
 
 	if (hw->mac.type == e1000_82571 || hw->mac.type == e1000_82572) {