mt76x02: add hrtimer for pre TBTT for USB

Add timer and work for pre TBTT for USB devices. For now code
doesn't do anyting useful, just add hrtimer which synchronize
with hardware MT_TBTT_TIMER.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt76x02.h

@@ -88,6 +88,9 @@ struct mt76x02_dev {
 	struct delayed_work mac_work;
 	struct delayed_work wdt_work;
 
+	struct hrtimer pre_tbtt_timer;
+	struct work_struct pre_tbtt_work;
+
 	u32 aggr_stats[32];
 
 	struct sk_buff *beacons[8];

drivers/net/wireless/mediatek/mt76/mt76x02_regs.h

@@ -356,7 +356,10 @@
 #define MT_BEACON_TIME_CFG_TSF_COMP	GENMASK(31, 24)
 
 #define MT_TBTT_SYNC_CFG		0x1118
-#define MT_TBTT_TIMER_CFG		0x1124
+#define MT_TSF_TIMER_DW0		0x111c
+#define MT_TSF_TIMER_DW1		0x1120
+#define MT_TBTT_TIMER			0x1124
+#define MT_TBTT_TIMER_VAL		GENMASK(16, 0)
 
 #define MT_INT_TIMER_CFG		0x1128
 #define MT_INT_TIMER_CFG_PRE_TBTT	GENMASK(15, 0)

drivers/net/wireless/mediatek/mt76/mt76x02_usb_core.c

@@ -105,8 +105,78 @@ int mt76x02u_tx_prepare_skb(struct mt76_dev *mdev, void *data,
 }
 EXPORT_SYMBOL_GPL(mt76x02u_tx_prepare_skb);
 
+/* Trigger pre-TBTT event 8 ms before TBTT */
+#define PRE_TBTT_USEC 8000
+static void mt76x02u_start_pre_tbtt_timer(struct mt76x02_dev *dev)
+{
+	u64 time;
+	u32 tbtt;
+
+	/* Get remaining TBTT in usec */
+	tbtt = mt76_get_field(dev, MT_TBTT_TIMER, MT_TBTT_TIMER_VAL);
+	tbtt *= 32;
+
+	if (tbtt <= PRE_TBTT_USEC) {
+		queue_work(system_highpri_wq, &dev->pre_tbtt_work);
+		return;
+	}
+
+	time = (tbtt - PRE_TBTT_USEC) * 1000ull;
+	hrtimer_start(&dev->pre_tbtt_timer, time, HRTIMER_MODE_REL);
+}
+
+static void mt76x02u_restart_pre_tbtt_timer(struct mt76x02_dev *dev)
+{
+	u32 tbtt, dw0, dw1;
+	u64 tsf, time;
+
+	/* Get remaining TBTT in usec */
+	tbtt = mt76_get_field(dev, MT_TBTT_TIMER, MT_TBTT_TIMER_VAL);
+	tbtt *= 32;
+
+	dw0 = mt76_rr(dev, MT_TSF_TIMER_DW0);
+	dw1 = mt76_rr(dev, MT_TSF_TIMER_DW1);
+	tsf = (u64)dw0 << 32 | dw1;
+	dev_dbg(dev->mt76.dev, "TSF: %llu us TBTT %u us\n", tsf, tbtt);
+
+	/* Convert beacon interval in TU (1024 usec) to nsec */
+	time = ((1000000000ull * dev->beacon_int) >> 10);
+
+	/* Adjust time to trigger hrtimer 8ms before TBTT */
+	if (tbtt < PRE_TBTT_USEC)
+		time -= (PRE_TBTT_USEC - tbtt) * 1000ull;
+	else
+		time += (tbtt - PRE_TBTT_USEC) * 1000ull;
+
+	hrtimer_start(&dev->pre_tbtt_timer, time, HRTIMER_MODE_REL);
+}
+
+static void mt76x02u_pre_tbtt_work(struct work_struct *work)
+{
+	struct mt76x02_dev *dev =
+		container_of(work, struct mt76x02_dev, pre_tbtt_work);
+
+	if (!dev->beacon_mask)
+		return;
+	mt76x02u_restart_pre_tbtt_timer(dev);
+}
+
+static enum hrtimer_restart mt76x02u_pre_tbtt_interrupt(struct hrtimer *timer)
+{
+	struct mt76x02_dev *dev =
+	    container_of(timer, struct mt76x02_dev, pre_tbtt_timer);
+
+	queue_work(system_highpri_wq, &dev->pre_tbtt_work);
+
+	return HRTIMER_NORESTART;
+}
+
 void mt76x02u_init_beacon_config(struct mt76x02_dev *dev)
 {
+	hrtimer_init(&dev->pre_tbtt_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	dev->pre_tbtt_timer.function = mt76x02u_pre_tbtt_interrupt;
+	INIT_WORK(&dev->pre_tbtt_work, mt76x02u_pre_tbtt_work);
+
 	mt76x02_init_beacon_config(dev);
 }
 EXPORT_SYMBOL_GPL(mt76x02u_init_beacon_config);