mt76: mt7615: fix using VHT STBC rates

The hardware expects MT_TX_RATE_NSS to be filled with the number of
space/time streams. For non-STBC rates, this is equal to nss.
For 1-stream STBC, this needs to be set to 2.
This is relevant for VHT rates only, on HT, the value is derived from MCS
internally.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/mac.c b/drivers/net/wireless/mediatek/mt76/mt7615/mac.c
index 5bfb4594b8ee4445f7643c9253dacdbd88f58871..6c21b2df69c45c2fe184182317831ed4059c8a8b 100644 (file)
--- a/drivers/net/wireless/mediatek/mt76/mt7615/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7615/mac.c
@@ -254,7 +254,7 @@ mt7615_mac_tx_rate_val(struct mt7615_dev *dev,
                       bool stbc, u8 *bw)
 {
        u8 phy, nss, rate_idx;
-       u16 rateval;
+       u16 rateval = 0;
 
        *bw = 0;
 
@@ -292,12 +292,14 @@ mt7615_mac_tx_rate_val(struct mt7615_dev *dev,
                rate_idx = val & 0xff;
        }
 
-       rateval = (FIELD_PREP(MT_TX_RATE_IDX, rate_idx) |
-                  FIELD_PREP(MT_TX_RATE_MODE, phy) |
-                  FIELD_PREP(MT_TX_RATE_NSS, nss - 1));
-
-       if (stbc && nss == 1)
+       if (stbc && nss == 1) {
+               nss++;
                rateval |= MT_TX_RATE_STBC;
+       }
+
+       rateval |= (FIELD_PREP(MT_TX_RATE_IDX, rate_idx) |
+                   FIELD_PREP(MT_TX_RATE_MODE, phy) |
+                   FIELD_PREP(MT_TX_RATE_NSS, nss - 1));
 
        return rateval;
 }
@@ -771,6 +773,10 @@ out:
                break;
        case MT_PHY_TYPE_VHT:
                final_nss = FIELD_GET(MT_TX_RATE_NSS, final_rate);
+
+               if ((final_rate & MT_TX_RATE_STBC) && final_nss)
+                       final_nss--;
+
                final_rate_flags |= IEEE80211_TX_RC_VHT_MCS;
                final_rate = (final_rate & MT_TX_RATE_IDX) | (final_nss << 4);
                break;