rt2x00: rt2800usb: rework txstatus code

Currently we read tx status register after each urb data transfer. As
callback procedure also trigger reading, that causing we have many
"threads" of reading status. To prevent that introduce TX_STATUS_READING
flags, and check if we are already in process of sequential reading
TX_STA_FIFO, before requesting new reads.

Change timer to hrtimer, that make TX_STA_FIFO overruns less possible.
Use 200 us for initial timeout, and then reschedule in 100 us period,
this values probably have to be tuned.

Make changes on txdone work. Schedule it from
rt2800usb_tx_sta_fifo_read_completed() callback when first valid status
show up. Check in callback if tx status timeout happens, and schedule
work on that condition too. That make possible to remove tx status
timeout from generic watchdog. I moved that to rt2800usb.

Loop in txdone work, that should prevent situation when we queue work,
which is already processed, and after finish work is not rescheduled
again.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 90 insertions, 30 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2800usb.c b/drivers/net/wireless/rt2x00/rt2800usb.c
index 4eaa6280f367..eacf94b2f382 100644
--- a/drivers/net/wireless/rt2x00/rt2800usb.c
+++ b/drivers/net/wireless/rt2x00/rt2800usb.c
@@ -114,45 +114,103 @@ static bool rt2800usb_txstatus_pending(struct rt2x00_dev *rt2x00dev)
 	return false;
 }
 
+static inline bool rt2800usb_entry_txstatus_timeout(struct queue_entry *entry)
+{
+	bool tout;
+
+	if (!test_bit(ENTRY_DATA_STATUS_PENDING, &entry->flags))
+		return false;
+
+	tout = time_after(jiffies, entry->last_action + msecs_to_jiffies(100));
+	if (unlikely(tout))
+		WARNING(entry->queue->rt2x00dev,
+			"TX status timeout for entry %d in queue %d\n",
+			entry->entry_idx, entry->queue->qid);
+	return tout;
+
+}
+
+static bool rt2800usb_txstatus_timeout(struct rt2x00_dev *rt2x00dev)
+{
+	struct data_queue *queue;
+	struct queue_entry *entry;
+
+	tx_queue_for_each(rt2x00dev, queue) {
+		entry = rt2x00queue_get_entry(queue, Q_INDEX_DONE);
+		if (rt2800usb_entry_txstatus_timeout(entry))
+			return true;
+	}
+	return false;
+}
+
 static bool rt2800usb_tx_sta_fifo_read_completed(struct rt2x00_dev *rt2x00dev,
 						 int urb_status, u32 tx_status)
 {
+	bool valid;
+
 	if (urb_status) {
-		WARNING(rt2x00dev, "rt2x00usb_register_read_async failed: %d\n", urb_status);
-		return false;
+		WARNING(rt2x00dev, "TX status read failed %d\n", urb_status);
+
+		goto stop_reading;
 	}
 
-	/* try to read all TX_STA_FIFO entries before scheduling txdone_work */
-	if (rt2x00_get_field32(tx_status, TX_STA_FIFO_VALID)) {
-		if (!kfifo_put(&rt2x00dev->txstatus_fifo, &tx_status)) {
-			WARNING(rt2x00dev, "TX status FIFO overrun, "
-				"drop tx status report.\n");
-			queue_work(rt2x00dev->workqueue, &rt2x00dev->txdone_work);
-		} else
-			return true;
-	} else if (!kfifo_is_empty(&rt2x00dev->txstatus_fifo)) {
+	valid = rt2x00_get_field32(tx_status, TX_STA_FIFO_VALID);
+	if (valid) {
+		if (!kfifo_put(&rt2x00dev->txstatus_fifo, &tx_status))
+			WARNING(rt2x00dev, "TX status FIFO overrun\n");
+
 		queue_work(rt2x00dev->workqueue, &rt2x00dev->txdone_work);
+
+		/* Reschedule urb to read TX status again instantly */
+		return true;
 	} else if (rt2800usb_txstatus_pending(rt2x00dev)) {
-		mod_timer(&rt2x00dev->txstatus_timer, jiffies + msecs_to_jiffies(2));
+		/* Read register after 250 us */
+		hrtimer_start(&rt2x00dev->txstatus_timer, ktime_set(0, 250000),
+			      HRTIMER_MODE_REL);
+		return false;
 	}
 
-	return false;
+stop_reading:
+	clear_bit(TX_STATUS_READING, &rt2x00dev->flags);
+	/*
+	 * There is small race window above, between txstatus pending check and
+	 * clear_bit someone could do rt2x00usb_interrupt_txdone, so recheck
+	 * here again if status reading is needed.
+	 */
+	if (rt2800usb_txstatus_pending(rt2x00dev) &&
+	    test_and_set_bit(TX_STATUS_READING, &rt2x00dev->flags))
+		return true;
+	else
+		return false;
+}
+
+static void rt2800usb_async_read_tx_status(struct rt2x00_dev *rt2x00dev)
+{
+
+	if (test_and_set_bit(TX_STATUS_READING, &rt2x00dev->flags))
+		return;
+
+	/* Read TX_STA_FIFO register after 500 us */
+	hrtimer_start(&rt2x00dev->txstatus_timer, ktime_set(0, 500000),
+		      HRTIMER_MODE_REL);
 }
 
 static void rt2800usb_tx_dma_done(struct queue_entry *entry)
 {
 	struct rt2x00_dev *rt2x00dev = entry->queue->rt2x00dev;
 
-	rt2x00usb_register_read_async(rt2x00dev, TX_STA_FIFO,
-				      rt2800usb_tx_sta_fifo_read_completed);
+	rt2800usb_async_read_tx_status(rt2x00dev);
 }
 
-static void rt2800usb_tx_sta_fifo_timeout(unsigned long data)
+static enum hrtimer_restart rt2800usb_tx_sta_fifo_timeout(struct hrtimer *timer)
 {
-	struct rt2x00_dev *rt2x00dev = (struct rt2x00_dev *)data;
+	struct rt2x00_dev *rt2x00dev =
+	    container_of(timer, struct rt2x00_dev, txstatus_timer);
 
 	rt2x00usb_register_read_async(rt2x00dev, TX_STA_FIFO,
 				      rt2800usb_tx_sta_fifo_read_completed);
+
+	return HRTIMER_NORESTART;
 }
 
 /*
@@ -540,7 +598,7 @@ static void rt2800usb_txdone_nostatus(struct rt2x00_dev *rt2x00dev)
 
 			if (test_bit(ENTRY_DATA_IO_FAILED, &entry->flags))
 				rt2x00lib_txdone_noinfo(entry, TXDONE_FAILURE);
-			else if (rt2x00queue_status_timeout(entry))
+			else if (rt2800usb_entry_txstatus_timeout(entry))
 				rt2x00lib_txdone_noinfo(entry, TXDONE_UNKNOWN);
 			else
 				break;
@@ -553,17 +611,21 @@ static void rt2800usb_work_txdone(struct work_struct *work)
 	struct rt2x00_dev *rt2x00dev =
 	    container_of(work, struct rt2x00_dev, txdone_work);
 
-	rt2800usb_txdone(rt2x00dev);
+	while (!kfifo_is_empty(&rt2x00dev->txstatus_fifo) ||
+	       rt2800usb_txstatus_timeout(rt2x00dev)) {
 
-	rt2800usb_txdone_nostatus(rt2x00dev);
+		rt2800usb_txdone(rt2x00dev);
 
-	/*
-	 * The hw may delay sending the packet after DMA complete
-	 * if the medium is busy, thus the TX_STA_FIFO entry is
-	 * also delayed -> use a timer to retrieve it.
-	 */
-	if (rt2800usb_txstatus_pending(rt2x00dev))
-		mod_timer(&rt2x00dev->txstatus_timer, jiffies + msecs_to_jiffies(2));
+		rt2800usb_txdone_nostatus(rt2x00dev);
+
+		/*
+		 * The hw may delay sending the packet after DMA complete
+		 * if the medium is busy, thus the TX_STA_FIFO entry is
+		 * also delayed -> use a timer to retrieve it.
+		 */
+		if (rt2800usb_txstatus_pending(rt2x00dev))
+			rt2800usb_async_read_tx_status(rt2x00dev);
+	}
 }
 
 /*
@@ -705,9 +767,7 @@ static int rt2800usb_probe_hw(struct rt2x00_dev *rt2x00dev)
 	__set_bit(REQUIRE_TXSTATUS_FIFO, &rt2x00dev->cap_flags);
 	__set_bit(REQUIRE_PS_AUTOWAKE, &rt2x00dev->cap_flags);
 
-	setup_timer(&rt2x00dev->txstatus_timer,
-		    rt2800usb_tx_sta_fifo_timeout,
-		    (unsigned long) rt2x00dev);
+	rt2x00dev->txstatus_timer.function = rt2800usb_tx_sta_fifo_timeout,
 
 	/*
 	 * Set the rssi offset.