wifi: mt76: fix rx checksum offload on mt7615/mt7915/mt7921

Checking the relevant rxd bits for the checksum information only indicates
if the checksum verification was performed by the hardware and doesn't show
actual checksum errors. Checksum errors are indicated in the info field of
the DMA descriptor. Fix packets erroneously marked as CHECKSUM_UNNECESSARY
by checking the extra bits as well.
Those bits are only passed to the driver for MMIO devices at the moment, so
limit checksum offload to those.

Fixes: 2122dfbf ("mt76: mt7615: add rx checksum offload support")
Fixes: 94244d2e ("mt76: mt7915: add rx checksum offload support")
Fixes: 0e757327 ("mt76: mt7921: enable rx csum offload")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221005130824.23371-2-nbd@nbd.name

drivers/net/wireless/mediatek/mt76/dma.c

@@ -696,10 +696,7 @@ mt76_dma_rx_process(struct mt76_dev *dev, struct mt76_queue *q, int budget)
 
 		skb_reserve(skb, q->buf_offset);
 
-		if (q == &dev->q_rx[MT_RXQ_MCU]) {
-			u32 *rxfce = (u32 *)skb->cb;
-			*rxfce = info;
-		}
+		*(u32 *)skb->cb = info;
 
 		__skb_put(skb, len);
 		done++;

drivers/net/wireless/mediatek/mt76/mt7615/mac.c

@@ -345,6 +345,7 @@ static int mt7615_mac_fill_rx(struct mt7615_dev *dev, struct sk_buff *skb)
 	u32 rxd1 = le32_to_cpu(rxd[1]);
 	u32 rxd2 = le32_to_cpu(rxd[2]);
 	u32 csum_mask = MT_RXD0_NORMAL_IP_SUM | MT_RXD0_NORMAL_UDP_TCP_SUM;
+	u32 csum_status = *(u32 *)skb->cb;
 	bool unicast, hdr_trans, remove_pad, insert_ccmp_hdr = false;
 	u16 hdr_gap;
 	int phy_idx;
@@ -394,7 +395,8 @@ static int mt7615_mac_fill_rx(struct mt7615_dev *dev, struct sk_buff *skb)
 		spin_unlock_bh(&dev->sta_poll_lock);
 	}
 
-	if ((rxd0 & csum_mask) == csum_mask)
+	if (mt76_is_mmio(&dev->mt76) && (rxd0 & csum_mask) == csum_mask &&
+	    !(csum_status & (BIT(0) | BIT(2) | BIT(3))))
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 
 	if (rxd2 & MT_RXD2_NORMAL_FCS_ERR)

drivers/net/wireless/mediatek/mt76/mt7915/mac.c

@@ -233,6 +233,7 @@ mt7915_mac_fill_rx(struct mt7915_dev *dev, struct sk_buff *skb)
 	u8 remove_pad, amsdu_info;
 	u8 mode = 0, qos_ctl = 0;
 	struct mt7915_sta *msta = NULL;
+	u32 csum_status = *(u32 *)skb->cb;
 	bool hdr_trans;
 	u16 hdr_gap;
 	u16 seq_ctrl = 0;
@@ -288,7 +289,8 @@ mt7915_mac_fill_rx(struct mt7915_dev *dev, struct sk_buff *skb)
 	if (!sband->channels)
 		return -EINVAL;
 
-	if ((rxd0 & csum_mask) == csum_mask)
+	if ((rxd0 & csum_mask) == csum_mask &&
+	    !(csum_status & (BIT(0) | BIT(2) | BIT(3))))
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 
 	if (rxd1 & MT_RXD1_NORMAL_FCS_ERR)

drivers/net/wireless/mediatek/mt76/mt7921/mac.c

@@ -230,6 +230,7 @@ mt7921_mac_fill_rx(struct mt7921_dev *dev, struct sk_buff *skb)
 	struct mt76_phy *mphy = &dev->mt76.phy;
 	struct mt7921_phy *phy = &dev->phy;
 	struct ieee80211_supported_band *sband;
+	u32 csum_status = *(u32 *)skb->cb;
 	u32 rxd0 = le32_to_cpu(rxd[0]);
 	u32 rxd1 = le32_to_cpu(rxd[1]);
 	u32 rxd2 = le32_to_cpu(rxd[2]);
@@ -290,7 +291,8 @@ mt7921_mac_fill_rx(struct mt7921_dev *dev, struct sk_buff *skb)
 	if (!sband->channels)
 		return -EINVAL;
 
-	if ((rxd0 & csum_mask) == csum_mask)
+	if (mt76_is_mmio(&dev->mt76) && (rxd0 & csum_mask) == csum_mask &&
+	    !(csum_status & (BIT(0) | BIT(2) | BIT(3))))
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 
 	if (rxd1 & MT_RXD1_NORMAL_FCS_ERR)