From: Peter Hessler <phessler@theapt.org>
Subject: Re: fix fatal firmware error when forcing iwx to 11a/b/g mode
To: tech@openbsd.org
Date: Tue, 10 Mar 2026 01:50:28 +0100

On 2026 Mar 09 (Mon) at 13:49:59 +0100 (+0100), Stefan Sperling wrote:
:Forcing iwx(4) into 11a/b/g mode produces a fatal firmware error with
:BZ firmware, and possibly other firmware, too. This also happens when
:I try to disable mimo with "ifconfig iwx0 nwflag nomimo".
:
:The driver does not take limitations of 11a/b/g modes into account while
:initializing Tx rate selection, which triggers some sanity checks in the
:firmware. The patch below fixes this.
:
:ok?
:

makes sense, and it follow what I understand of 802.11.

Minor nit, can we get defines for htole16(3895) and htole16(3839) ?  Not
a blocker, but magic numbers gives me hives.

OK

Tested on ax211 that is switching between 11n/11ac/11g whie traveling.


:M  sys/dev/pci/if_iwx.c  |  24+  10-
:
:1 file changed, 24 insertions(+), 10 deletions(-)
:
:path + /usr/src
:commit - bf3713f7dfbf19ede85da952a0d01b849aa8a252
:blob - e731cf032ef66ed7a7eab46a3669fc5d80d9e8d3
:file + sys/dev/pci/if_iwx.c
:--- sys/dev/pci/if_iwx.c
:+++ sys/dev/pci/if_iwx.c
:@@ -8483,18 +8483,25 @@ iwx_rs_init_v3(struct iwx_softc *sc, struct iwx_node *
: 		cfg_cmd.mode = IWX_TLC_MNG_MODE_NON_HT;
: 
: 	cfg_cmd.sta_id = IWX_STATION_ID;
:-	if (in->in_phyctxt->vht_chan_width == IEEE80211_VHTOP0_CHAN_WIDTH_80)
:+	if ((ni->ni_flags & IEEE80211_NODE_VHT) &&
:+	    in->in_phyctxt->vht_chan_width == IEEE80211_VHTOP0_CHAN_WIDTH_80)
: 		cfg_cmd.max_ch_width = IWX_TLC_MNG_CH_WIDTH_80MHZ;
:-	else if (in->in_phyctxt->sco == IEEE80211_HTOP0_SCO_SCA ||
:-	    in->in_phyctxt->sco == IEEE80211_HTOP0_SCO_SCB)
:+	else if ((ni->ni_flags & IEEE80211_NODE_HT) &&
:+	    (in->in_phyctxt->sco == IEEE80211_HTOP0_SCO_SCA ||
:+	    in->in_phyctxt->sco == IEEE80211_HTOP0_SCO_SCB))
: 		cfg_cmd.max_ch_width = IWX_TLC_MNG_CH_WIDTH_40MHZ;
: 	else
: 		cfg_cmd.max_ch_width = IWX_TLC_MNG_CH_WIDTH_20MHZ;
:-	cfg_cmd.chains = IWX_TLC_MNG_CHAIN_A_MSK | IWX_TLC_MNG_CHAIN_B_MSK;
:+	if ((ni->ni_flags & IEEE80211_NODE_HT) && iwx_mimo_enabled(sc))
:+		cfg_cmd.chains = IWX_TLC_MNG_CHAIN_A_MSK | IWX_TLC_MNG_CHAIN_B_MSK;
:+	else
:+		cfg_cmd.chains = IWX_TLC_MNG_CHAIN_A_MSK;
: 	if (ni->ni_flags & IEEE80211_NODE_VHT)
: 		cfg_cmd.max_mpdu_len = htole16(3895);
:-	else
:+	else if (ni->ni_flags & IEEE80211_NODE_HT)
: 		cfg_cmd.max_mpdu_len = htole16(3839);
:+	else
:+		cfg_cmd.max_mpdu_len = IEEE80211_MAX_LEN;
: 	if (ni->ni_flags & IEEE80211_NODE_HT) {
: 		if (ieee80211_node_supports_ht_sgi20(ni)) {
: 			cfg_cmd.sgi_ch_width_supp |= (1 <<
:@@ -8551,18 +8558,25 @@ iwx_rs_init_v4(struct iwx_softc *sc, struct iwx_node *
: 		cfg_cmd.mode = IWX_TLC_MNG_MODE_NON_HT;
: 
: 	cfg_cmd.sta_id = IWX_STATION_ID;
:-	if (in->in_phyctxt->vht_chan_width == IEEE80211_VHTOP0_CHAN_WIDTH_80)
:+	if ((ni->ni_flags & IEEE80211_NODE_VHT) &&
:+	    in->in_phyctxt->vht_chan_width == IEEE80211_VHTOP0_CHAN_WIDTH_80)
: 		cfg_cmd.max_ch_width = IWX_TLC_MNG_CH_WIDTH_80MHZ;
:-	else if (in->in_phyctxt->sco == IEEE80211_HTOP0_SCO_SCA ||
:-	    in->in_phyctxt->sco == IEEE80211_HTOP0_SCO_SCB)
:+	else if ((ni->ni_flags & IEEE80211_NODE_HT) &&
:+	    (in->in_phyctxt->sco == IEEE80211_HTOP0_SCO_SCA ||
:+	    in->in_phyctxt->sco == IEEE80211_HTOP0_SCO_SCB))
: 		cfg_cmd.max_ch_width = IWX_TLC_MNG_CH_WIDTH_40MHZ;
: 	else
: 		cfg_cmd.max_ch_width = IWX_TLC_MNG_CH_WIDTH_20MHZ;
:-	cfg_cmd.chains = IWX_TLC_MNG_CHAIN_A_MSK | IWX_TLC_MNG_CHAIN_B_MSK;
:+	if ((ni->ni_flags & IEEE80211_NODE_HT) && iwx_mimo_enabled(sc))
:+		cfg_cmd.chains = IWX_TLC_MNG_CHAIN_A_MSK | IWX_TLC_MNG_CHAIN_B_MSK;
:+	else
:+		cfg_cmd.chains = IWX_TLC_MNG_CHAIN_A_MSK;
: 	if (ni->ni_flags & IEEE80211_NODE_VHT)
: 		cfg_cmd.max_mpdu_len = htole16(3895);
:-	else
:+	else if (ni->ni_flags & IEEE80211_NODE_HT)
: 		cfg_cmd.max_mpdu_len = htole16(3839);
:+	else
:+		cfg_cmd.max_mpdu_len = IEEE80211_MAX_LEN;
: 	if (ni->ni_flags & IEEE80211_NODE_HT) {
: 		if (ieee80211_node_supports_ht_sgi20(ni)) {
: 			cfg_cmd.sgi_ch_width_supp |= (1 <<
:

-- 
To a Real Woman, every ejaculation is premature.