wifi: mt76: mt7915: improve accuracy of time_busy calculation

The MIB INFO command is fetching MIB_BUSY_TIME, MIB_TX_TIME, MIB_RX_TIME and
MIB_OBSS_AIRTIME from the radio and filling out cc_busy, cc_tx, cc_bss_rx
and cc_rx respectively.

busy should be >= tx + rx >= tx + bss_rx but we don’t always quite see this.
Sometimes tx + rx is a bit higher than busy due to inaccurate accounting,
so this patch recalculates numbers to make them more reasonable.

Reported-By: Kevin Schneider <kevin.schneider@adtran.com>
Tested-by: Kevin Schneider <kevin.schneider@adtran.com>
Tested-by: Chad Monroe <chad.monroe@smartrg.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

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

@@ -444,6 +444,23 @@ mt7915_mac_init_band(struct mt7915_dev *dev, u8 band)
 
 	/* mt7915: disable rx rate report by default due to hw issues */
 	mt76_clear(dev, MT_DMA_DCR0(band), MT_DMA_DCR0_RXD_G5_EN);
+
+	/* clear estimated value of EIFS for Rx duration & OBSS time */
+	mt76_wr(dev, MT_WF_RMAC_RSVD0(band), MT_WF_RMAC_RSVD0_EIFS_CLR);
+
+	/* clear backoff time for Rx duration  */
+	mt76_clear(dev, MT_WF_RMAC_MIB_AIRTIME1(band),
+		   MT_WF_RMAC_MIB_NONQOSD_BACKOFF);
+	mt76_clear(dev, MT_WF_RMAC_MIB_AIRTIME3(band),
+		   MT_WF_RMAC_MIB_QOS01_BACKOFF);
+	mt76_clear(dev, MT_WF_RMAC_MIB_AIRTIME4(band),
+		   MT_WF_RMAC_MIB_QOS23_BACKOFF);
+
+	/* clear backoff time and set software compensation for OBSS time */
+	mask = MT_WF_RMAC_MIB_OBSS_BACKOFF | MT_WF_RMAC_MIB_ED_OFFSET;
+	set = FIELD_PREP(MT_WF_RMAC_MIB_OBSS_BACKOFF, 0) |
+	      FIELD_PREP(MT_WF_RMAC_MIB_ED_OFFSET, 4);
+	mt76_rmw(dev, MT_WF_RMAC_MIB_AIRTIME0(band), mask, set);
 }
 
 static void mt7915_mac_init(struct mt7915_dev *dev)

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

@@ -2940,25 +2940,36 @@ int mt7915_mcu_get_chan_mib_info(struct mt7915_phy *phy, bool chan_switch)
 {
 	/* strict order */
 	static const u32 offs[] = {
-		MIB_BUSY_TIME, MIB_TX_TIME, MIB_RX_TIME, MIB_OBSS_AIRTIME,
+		MIB_NON_WIFI_TIME,
-		MIB_BUSY_TIME_V2, MIB_TX_TIME_V2, MIB_RX_TIME_V2,
+		MIB_TX_TIME,
+		MIB_RX_TIME,
+		MIB_OBSS_AIRTIME,
+		MIB_TXOP_INIT_COUNT,
+		/* v2 */
+		MIB_NON_WIFI_TIME_V2,
+		MIB_TX_TIME_V2,
+		MIB_RX_TIME_V2,
 		MIB_OBSS_AIRTIME_V2
 	};
 	struct mt76_channel_state *state = phy->mt76->chan_state;
 	struct mt76_channel_state *state_ts = &phy->state_ts;
 	struct mt7915_dev *dev = phy->dev;
-	struct mt7915_mcu_mib *res, req[4];
+	struct mt7915_mcu_mib *res, req[5];
 	struct sk_buff *skb;
 	int i, ret, start = 0, ofs = 20;
+	u64 cc_tx;
 
 	if (!is_mt7915(&dev->mt76)) {
-		start = 4;
+		start = 5;
 		ofs = 0;
 	}
 
-	for (i = 0; i < 4; i++) {
+	for (i = 0; i < 5; i++) {
 		req[i].band = cpu_to_le32(phy != &dev->phy);
 		req[i].offs = cpu_to_le32(offs[i + start]);
+
+		if (!is_mt7915(&dev->mt76) && i == 3)
+			break;
 	}
 
 	ret = mt76_mcu_send_and_get_msg(&dev->mt76, MCU_EXT_CMD(GET_MIB_INFO),
@@ -2968,20 +2979,24 @@ int mt7915_mcu_get_chan_mib_info(struct mt7915_phy *phy, bool chan_switch)
 
 	res = (struct mt7915_mcu_mib *)(skb->data + ofs);
 
+#define __res_u64(s) le64_to_cpu(res[s].data)
+	/* subtract Tx backoff time from Tx duration */
+	cc_tx = is_mt7915(&dev->mt76) ? __res_u64(1) - __res_u64(4) : __res_u64(1);
+
 	if (chan_switch)
 		goto out;
 
-#define __res_u64(s) le64_to_cpu(res[s].data)
+	state->cc_tx += cc_tx - state_ts->cc_tx;
-	state->cc_busy += __res_u64(0) - state_ts->cc_busy;
-	state->cc_tx += __res_u64(1) - state_ts->cc_tx;
 	state->cc_bss_rx += __res_u64(2) - state_ts->cc_bss_rx;
 	state->cc_rx += __res_u64(2) + __res_u64(3) - state_ts->cc_rx;
+	state->cc_busy += __res_u64(0) + cc_tx + __res_u64(2) + __res_u64(3) -
+			  state_ts->cc_busy;
 
 out:
-	state_ts->cc_busy = __res_u64(0);
+	state_ts->cc_tx = cc_tx;
-	state_ts->cc_tx = __res_u64(1);
 	state_ts->cc_bss_rx = __res_u64(2);
 	state_ts->cc_rx = __res_u64(2) + __res_u64(3);
+	state_ts->cc_busy = __res_u64(0) + cc_tx + __res_u64(2) + __res_u64(3);
 #undef __res_u64
 
 	dev_kfree_skb(skb);

drivers/net/wireless/mediatek/mt76/mt7915/mcu.h

@@ -160,15 +160,17 @@ struct mt7915_mcu_mib {
 
 enum mt7915_chan_mib_offs {
 	/* mt7915 */
-	MIB_BUSY_TIME = 14,
 	MIB_TX_TIME = 81,
 	MIB_RX_TIME,
 	MIB_OBSS_AIRTIME = 86,
+	MIB_NON_WIFI_TIME,
+	MIB_TXOP_INIT_COUNT,
+
 	/* mt7916 */
-	MIB_BUSY_TIME_V2 = 0,
 	MIB_TX_TIME_V2 = 6,
 	MIB_RX_TIME_V2 = 8,
-	MIB_OBSS_AIRTIME_V2 = 490
+	MIB_OBSS_AIRTIME_V2 = 490,
+	MIB_NON_WIFI_TIME_V2
 };
 
 struct edca {

drivers/net/wireless/mediatek/mt76/mt7915/regs.h

@@ -525,8 +525,22 @@ enum offs_rev {
 #define MT_WF_RFCR1_DROP_CFEND		BIT(7)
 #define MT_WF_RFCR1_DROP_CFACK		BIT(8)
 
+#define MT_WF_RMAC_RSVD0(_band)	MT_WF_RMAC(_band, 0x02e0)
+#define MT_WF_RMAC_RSVD0_EIFS_CLR	BIT(21)
+
 #define MT_WF_RMAC_MIB_AIRTIME0(_band)	MT_WF_RMAC(_band, 0x0380)
 #define MT_WF_RMAC_MIB_RXTIME_CLR	BIT(31)
+#define MT_WF_RMAC_MIB_OBSS_BACKOFF	GENMASK(15, 0)
+#define MT_WF_RMAC_MIB_ED_OFFSET	GENMASK(20, 16)
+
+#define MT_WF_RMAC_MIB_AIRTIME1(_band)	MT_WF_RMAC(_band, 0x0384)
+#define MT_WF_RMAC_MIB_NONQOSD_BACKOFF	GENMASK(31, 16)
+
+#define MT_WF_RMAC_MIB_AIRTIME3(_band)	MT_WF_RMAC(_band, 0x038c)
+#define MT_WF_RMAC_MIB_QOS01_BACKOFF	GENMASK(31, 0)
+
+#define MT_WF_RMAC_MIB_AIRTIME4(_band)	MT_WF_RMAC(_band, 0x0390)
+#define MT_WF_RMAC_MIB_QOS23_BACKOFF	GENMASK(31, 0)
 
 /* WFDMA0 */
 #define MT_WFDMA0_BASE			__REG(WFDMA0_ADDR)