Re: [PATCH v2] wifi: mt76: mt7915: remove BW160 and BW80+80 support

[Oleksandr Natalenko <oleksandr@natalenko.name>]

Hello.

On středa 4. ledna 2023 10:03:52 CEST MeiChia Chiu wrote:
> Remove BW160 and BW80+80 capability in mt7915.
> 
> Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> Reviewed-by: Ryder Lee <ryder.lee@mediatek.com>
> Reviewed-by: Shayne Chen <shayne.chen@mediatek.com>
> Signed-off-by: Money Wang<Money.Wang@mediatek.com>
> Signed-off-by: MeiChia Chiu <MeiChia.Chiu@mediatek.com>
> ---
> v2: update commit message and title
> ---
>  .../net/wireless/mediatek/mt76/mt7915/init.c  | 38 +++++--------------
>  1 file changed, 9 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/init.c b/drivers/net/wireless/mediatek/mt76/mt7915/init.c
> index 571c94835942..c72d673f02dd 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7915/init.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7915/init.c
> @@ -38,8 +38,7 @@ static const struct ieee80211_iface_combination if_comb[] = {
>  				       BIT(NL80211_CHAN_WIDTH_20) |
>  				       BIT(NL80211_CHAN_WIDTH_40) |
>  				       BIT(NL80211_CHAN_WIDTH_80) |
> -				       BIT(NL80211_CHAN_WIDTH_160) |
> -				       BIT(NL80211_CHAN_WIDTH_80P80),
> +				       BIT(NL80211_CHAN_WIDTH_160),
>  	}
>  };
>  
> @@ -394,11 +393,6 @@ mt7915_init_wiphy(struct mt7915_phy *phy)
>  			phy->mt76->sband_5g.sband.vht_cap.cap |=
>  				IEEE80211_VHT_CAP_MAX_MPDU_LENGTH_7991 |
>  				IEEE80211_VHT_CAP_MAX_A_MPDU_LENGTH_EXPONENT_MASK;
> -
> -			if (!dev->dbdc_support)
> -				phy->mt76->sband_5g.sband.vht_cap.cap |=
> -					IEEE80211_VHT_CAP_SHORT_GI_160 |
> -					IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160_80PLUS80MHZ;
>  		} else {
>  			phy->mt76->sband_5g.sband.vht_cap.cap |=
>  				IEEE80211_VHT_CAP_MAX_MPDU_LENGTH_11454 |
> @@ -834,13 +828,9 @@ mt7915_set_stream_he_txbf_caps(struct mt7915_phy *phy,
>  	int sts = hweight8(phy->mt76->chainmask);
>  	u8 c, sts_160 = sts;
>  
> -	/* Can do 1/2 of STS in 160Mhz mode for mt7915 */
> -	if (is_mt7915(&dev->mt76)) {
> -		if (!dev->dbdc_support)
> -			sts_160 /= 2;
> -		else
> -			sts_160 = 0;
> -	}
> +	/* mt7915 doesn't support bw160 */
> +	if (is_mt7915(&dev->mt76))
> +		sts_160 = 0;
>  
>  #ifdef CONFIG_MAC80211_MESH
>  	if (vif == NL80211_IFTYPE_MESH_POINT)
> @@ -894,9 +884,6 @@ mt7915_set_stream_he_txbf_caps(struct mt7915_phy *phy,
>  	elem->phy_cap_info[3] |= IEEE80211_HE_PHY_CAP3_SU_BEAMFORMER;
>  	elem->phy_cap_info[4] |= IEEE80211_HE_PHY_CAP4_MU_BEAMFORMER;
>  
> -	/* num_snd_dim
> -	 * for mt7915, max supported sts is 2 for bw > 80MHz and 0 if dbdc
> -	 */
>  	c = FIELD_PREP(IEEE80211_HE_PHY_CAP5_BEAMFORMEE_NUM_SND_DIM_UNDER_80MHZ_MASK,
>  		       sts - 1);
>  	if (sts_160)
> @@ -944,15 +931,10 @@ mt7915_init_he_caps(struct mt7915_phy *phy, enum nl80211_band band,
>  	int i, idx = 0, nss = hweight8(phy->mt76->antenna_mask);
>  	u16 mcs_map = 0;
>  	u16 mcs_map_160 = 0;
> -	u8 nss_160;
> +	u8 nss_160 = nss;
>  
> -	if (!is_mt7915(&dev->mt76))
> -		nss_160 = nss;
> -	else if (!dev->dbdc_support)
> -		/* Can do 1/2 of NSS streams in 160Mhz mode for mt7915 */
> -		nss_160 = nss / 2;
> -	else
> -		/* Can't do 160MHz with mt7915 dbdc */
> +	/* Can't do 160MHz with mt7915 */
> +	if (is_mt7915(&dev->mt76))
>  		nss_160 = 0;
>  
>  	for (i = 0; i < 8; i++) {
> @@ -1002,8 +984,7 @@ mt7915_init_he_caps(struct mt7915_phy *phy, enum nl80211_band band,
>  		else if (nss_160)
>  			he_cap_elem->phy_cap_info[0] =
>  				IEEE80211_HE_PHY_CAP0_CHANNEL_WIDTH_SET_40MHZ_80MHZ_IN_5G |
> -				IEEE80211_HE_PHY_CAP0_CHANNEL_WIDTH_SET_160MHZ_IN_5G |
> -				IEEE80211_HE_PHY_CAP0_CHANNEL_WIDTH_SET_80PLUS80_MHZ_IN_5G;
> +				IEEE80211_HE_PHY_CAP0_CHANNEL_WIDTH_SET_160MHZ_IN_5G;
>  		else
>  			he_cap_elem->phy_cap_info[0] =
>  				IEEE80211_HE_PHY_CAP0_CHANNEL_WIDTH_SET_40MHZ_80MHZ_IN_5G;
> @@ -1075,12 +1056,11 @@ mt7915_init_he_caps(struct mt7915_phy *phy, enum nl80211_band band,
>  			break;
>  		}
>  
> +		memset(he_mcs, 0, sizeof(*he_mcs));
>  		he_mcs->rx_mcs_80 = cpu_to_le16(mcs_map);
>  		he_mcs->tx_mcs_80 = cpu_to_le16(mcs_map);
>  		he_mcs->rx_mcs_160 = cpu_to_le16(mcs_map_160);
>  		he_mcs->tx_mcs_160 = cpu_to_le16(mcs_map_160);
> -		he_mcs->rx_mcs_80p80 = cpu_to_le16(mcs_map_160);
> -		he_mcs->tx_mcs_80p80 = cpu_to_le16(mcs_map_160);
>  
>  		mt7915_set_stream_he_txbf_caps(phy, he_cap, i);

I was negatively surprised by this as I had `VHT160-80PLUS80` in my hostapd config file, and the AP worked just fine, and stopped working after upgrading the machine to v6.3.

I do understand that the chip doesn't support 80+80, and my AP just works in VHT160 mode, so replacing `VHT160-80PLUS80` with `VHT160` in the config fixed the issue for me. Thanks for bringing BW160 back later in c2f73eacee3b.

But I do want to point out that the commit message should explain the reason for removal. Also, I'm one of those users of:

```
01:00.0 Unclassified device [0002]: MEDIATEK Corp. MT7915E 802.11ax PCI Express Wireless Network Adapter
```

for whom BW160 works just fine.

Thanks.

-- 
Oleksandr Natalenko (post-factum)