mt76: mt7915: fix rx fcs error count in testmode

FCS error packets are filtered by default and won't be reported to
driver, so that RX fcs error and PER in testmode always show zero.
Fix this issue by reading fcs error count from hw counter.

We did't fix this issue by disabling fcs error rx filter since it may
let HW suffer some SER errors.

Fixes: 5d8a83f0 ("mt76: mt7915: implement testmode rx support")
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

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

@@ -464,10 +464,17 @@ mt7915_tm_set_tx_frames(struct mt7915_phy *phy, bool en)
 static void
 mt7915_tm_set_rx_frames(struct mt7915_phy *phy, bool en)
 {
-	if (en)
+	mt7915_tm_set_trx(phy, TM_MAC_RX_RXV, false);
+
+	if (en) {
+		struct mt7915_dev *dev = phy->dev;
+
 		mt7915_tm_update_channel(phy);
 
-	mt7915_tm_set_trx(phy, TM_MAC_RX_RXV, en);
+		/* read-clear */
+		mt76_rr(dev, MT_MIB_SDR3(phy != &dev->phy));
+		mt7915_tm_set_trx(phy, TM_MAC_RX_RXV, en);
+	}
 }
 
 static int
@@ -690,7 +697,11 @@ static int
 mt7915_tm_dump_stats(struct mt76_phy *mphy, struct sk_buff *msg)
 {
 	struct mt7915_phy *phy = mphy->priv;
+	struct mt7915_dev *dev = phy->dev;
+	bool ext_phy = phy != &dev->phy;
+	enum mt76_rxq_id q;
 	void *rx, *rssi;
+	u16 fcs_err;
 	int i;
 
 	rx = nla_nest_start(msg, MT76_TM_STATS_ATTR_LAST_RX);
@@ -735,6 +746,12 @@ mt7915_tm_dump_stats(struct mt76_phy *mphy, struct sk_buff *msg)
 
 	nla_nest_end(msg, rx);
 
+	fcs_err = mt76_get_field(dev, MT_MIB_SDR3(ext_phy),
+				 MT_MIB_SDR3_FCS_ERR_MASK);
+	q = ext_phy ? MT_RXQ_EXT : MT_RXQ_MAIN;
+	mphy->test.rx_stats.packets[q] += fcs_err;
+	mphy->test.rx_stats.fcs_error[q] += fcs_err;
+
 	return 0;
 }