A PHY supporting 160Mhz with a reduced number of NSS may not have any
of the IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK bits set.
For exemple, the QCA9984 is 4x4, but can only do 2x2 VHT160 or
80+80. The corresponding VHT capabilities should be:
- IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK == 0
- Extended NSS BW == 2
If we use that hardware in AP mode, and a 160Mhz 2x2 STA without NSS
restriction connects to it, then that STA will set
IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK to 1.
The usual logic of using bitwise-and with our own capabilities does
not work here, the current code clears the SUPP_CHAN_WIDTH bits and
resolve STA bandwidth to 80Mhz instead of 160Mhz, fix this.
Signed-off-by: Maxime Bizon <[email protected]>
---
net/mac80211/vht.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/mac80211/vht.c b/net/mac80211/vht.c
index e856f9092137..7ef93adc4f24 100644
--- a/net/mac80211/vht.c
+++ b/net/mac80211/vht.c
@@ -230,9 +230,11 @@ ieee80211_vht_cap_ie_to_sta_vht_cap(struct ieee80211_sub_if_data *sdata,
sizeof(struct ieee80211_vht_mcs_info));
/* copy EXT_NSS_BW Support value or remove the capability */
- if (ieee80211_hw_check(&sdata->local->hw, SUPPORTS_VHT_EXT_NSS_BW))
+ if (ieee80211_hw_check(&sdata->local->hw, SUPPORTS_VHT_EXT_NSS_BW)) {
+ vht_cap->cap |= cap_info &
+ IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK;
vht_cap->cap |= (cap_info & IEEE80211_VHT_CAP_EXT_NSS_BW_MASK);
- else
+ } else
vht_cap->vht_mcs.tx_highest &=
~cpu_to_le16(IEEE80211_VHT_EXT_NSS_BW_CAPABLE);
--
2.17.1
On 5/16/2022 1:39 AM, Maxime Bizon wrote:
>
> A PHY supporting 160Mhz with a reduced number of NSS may not have any
note correct abbreviation is: MHz
and it is suggested to use a space to separate the value from the units
> of the IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK bits set.
>
> For exemple, the QCA9984 is 4x4, but can only do 2x2 VHT160 or
s/exemple/example/
> 80+80. The corresponding VHT capabilities should be:
> - IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK == 0
> - Extended NSS BW == 2
>
> If we use that hardware in AP mode, and a 160Mhz 2x2 STA without NSS
> restriction connects to it, then that STA will set
> IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK to 1.
>
> The usual logic of using bitwise-and with our own capabilities does
> not work here, the current code clears the SUPP_CHAN_WIDTH bits and
> resolve STA bandwidth to 80Mhz instead of 160Mhz, fix this.
>
> Signed-off-by: Maxime Bizon <[email protected]>
> ---
> net/mac80211/vht.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/mac80211/vht.c b/net/mac80211/vht.c
> index e856f9092137..7ef93adc4f24 100644
> --- a/net/mac80211/vht.c
> +++ b/net/mac80211/vht.c
> @@ -230,9 +230,11 @@ ieee80211_vht_cap_ie_to_sta_vht_cap(struct ieee80211_sub_if_data *sdata,
> sizeof(struct ieee80211_vht_mcs_info));
>
> /* copy EXT_NSS_BW Support value or remove the capability */
> - if (ieee80211_hw_check(&sdata->local->hw, SUPPORTS_VHT_EXT_NSS_BW))
> + if (ieee80211_hw_check(&sdata->local->hw, SUPPORTS_VHT_EXT_NSS_BW)) {
> + vht_cap->cap |= cap_info &
> + IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK;
> vht_cap->cap |= (cap_info & IEEE80211_VHT_CAP_EXT_NSS_BW_MASK);
> - else
> + } else
per the coding style when you use braces on any leg of if/else, use them
on all legs
> vht_cap->vht_mcs.tx_highest &=
> ~cpu_to_le16(IEEE80211_VHT_EXT_NSS_BW_CAPABLE);
>
Applied on 5.19 and worked.
AP: QCA9984
STA：AX201
Before patch:
iw dev wlan-ax201 link
rx bitrate: 866 MBit/s VHT-MCS 9 160MHz short GI VHT-NSS 1
tx bitrate: 866 MBit/s VHT-MCS 9 80MHz short GI VHT-NSS 2
After patch:
rx bitrate: 866 MBit/s VHT-MCS 9 160MHz short GI VHT-NSS 1
tx bitrate: 866 MBit/s VHT-MCS 9 160MHz short GI VHT-NSS 1
Notice that the tx rate did not change and the NSS reduced from 2 to 1.
But actually it should support VHT-NSS 2 and achieve 1733 MBit/s at least
for rx bitrate (verified this with the same AP/STA using another OS,
and iperf showed 1.2GBit/s). Do you have any idea to fix that?
Although it is beyond the scope of this patch.
with iw 5.19 ax201 showed
VHT RX highest supported: 0 Mbps
VHT TX highest supported: 0 Mbps
VHT extended NSS: supported