ioat: switch watchdog and reset handler from workqueue to timer

In order to support dynamic resizing of the descriptor ring or polling
for a descriptor in the presence of a hung channel the reset handler
needs to make progress while in a non-preemptible context.  The current
workqueue implementation precludes polling channel reset completion
under spin_lock().

This conversion also allows us to return to opportunistic cleanup in the
ioat2 case as the timer implementation guarantees at least one cleanup
after every descriptor is submitted.  This means the worst case
completion latency becomes the timer frequency (for exceptional
circumstances), but with the benefit of avoiding busy waiting when the
lock is contended.

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 138 insertions, 183 deletions

diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index 1aa2974..72e59a0 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -49,7 +49,7 @@ static void __ioat2_issue_pending(struct ioat2_dma_chan *ioat)
 	void * __iomem reg_base = ioat->base.reg_base;
 
 	ioat->pending = 0;
-	ioat->dmacount += ioat2_ring_pending(ioat);
+	ioat->dmacount += ioat2_ring_pending(ioat);;
 	ioat->issued = ioat->head;
 	/* make descriptor updates globally visible before notifying channel */
 	wmb();
@@ -92,7 +92,6 @@ static void ioat2_update_pending(struct ioat2_dma_chan *ioat)
 
 static void __ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
 {
-	void __iomem *reg_base = ioat->base.reg_base;
 	struct ioat_ring_ent *desc;
 	struct ioat_dma_descriptor *hw;
 	int idx;
@@ -118,10 +117,7 @@ static void __ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
 	hw->src_addr = 0;
 	hw->dst_addr = 0;
 	async_tx_ack(&desc->txd);
-	writel(((u64) desc->txd.phys) & 0x00000000FFFFFFFF,
-	       reg_base + IOAT2_CHAINADDR_OFFSET_LOW);
-	writel(((u64) desc->txd.phys) >> 32,
-	       reg_base + IOAT2_CHAINADDR_OFFSET_HIGH);
+	ioat2_set_chainaddr(ioat, desc->txd.phys);
 	dump_desc_dbg(ioat, desc);
 	__ioat2_issue_pending(ioat);
 }
@@ -133,177 +129,14 @@ static void ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
 	spin_unlock_bh(&ioat->ring_lock);
 }
 
-static void ioat2_cleanup(struct ioat2_dma_chan *ioat);
-
-/**
- * ioat2_reset_part2 - reinit the channel after a reset
- */
-static void ioat2_reset_part2(struct work_struct *work)
-{
-	struct ioat_chan_common *chan;
-	struct ioat2_dma_chan *ioat;
-
-	chan = container_of(work, struct ioat_chan_common, work.work);
-	ioat = container_of(chan, struct ioat2_dma_chan, base);
-
-	/* ensure that ->tail points to the stalled descriptor
-	 * (ioat->pending is set to 2 at this point so no new
-	 * descriptors will be issued while we perform this cleanup)
-	 */
-	ioat2_cleanup(ioat);
-
-	spin_lock_bh(&chan->cleanup_lock);
-	spin_lock_bh(&ioat->ring_lock);
-
-	/* set the tail to be re-issued */
-	ioat->issued = ioat->tail;
-	ioat->dmacount = 0;
-
-	dev_dbg(to_dev(&ioat->base),
-		"%s: head: %#x tail: %#x issued: %#x count: %#x\n",
-		__func__, ioat->head, ioat->tail, ioat->issued, ioat->dmacount);
-
-	if (ioat2_ring_pending(ioat)) {
-		struct ioat_ring_ent *desc;
-
-		desc = ioat2_get_ring_ent(ioat, ioat->tail);
-		writel(((u64) desc->txd.phys) & 0x00000000FFFFFFFF,
-		       chan->reg_base + IOAT2_CHAINADDR_OFFSET_LOW);
-		writel(((u64) desc->txd.phys) >> 32,
-		       chan->reg_base + IOAT2_CHAINADDR_OFFSET_HIGH);
-		__ioat2_issue_pending(ioat);
-	} else
-		__ioat2_start_null_desc(ioat);
-
-	spin_unlock_bh(&ioat->ring_lock);
-	spin_unlock_bh(&chan->cleanup_lock);
-
-	dev_info(to_dev(chan),
-		 "chan%d reset - %d descs waiting, %d total desc\n",
-		 chan_num(chan), ioat->dmacount, 1 << ioat->alloc_order);
-}
-
-/**
- * ioat2_reset_channel - restart a channel
- * @ioat: IOAT DMA channel handle
- */
-static void ioat2_reset_channel(struct ioat2_dma_chan *ioat)
+static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
 {
-	u32 chansts, chanerr;
 	struct ioat_chan_common *chan = &ioat->base;
-	u16 active;
-
-	spin_lock_bh(&ioat->ring_lock);
-	active = ioat2_ring_active(ioat);
-	spin_unlock_bh(&ioat->ring_lock);
-	if (!active)
-		return;
-
-	chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
-	chansts = *chan->completion & IOAT_CHANSTS_DMA_TRANSFER_STATUS;
-	if (chanerr) {
-		dev_err(to_dev(chan),
-			"chan%d, CHANSTS = 0x%08x CHANERR = 0x%04x, clearing\n",
-			chan_num(chan), chansts, chanerr);
-		writel(chanerr, chan->reg_base + IOAT_CHANERR_OFFSET);
-	}
-
-	spin_lock_bh(&ioat->ring_lock);
-	ioat->pending = 2;
-	writeb(IOAT_CHANCMD_RESET,
-	       chan->reg_base
-	       + IOAT_CHANCMD_OFFSET(chan->device->version));
-	spin_unlock_bh(&ioat->ring_lock);
-	schedule_delayed_work(&chan->work, RESET_DELAY);
-}
-
-/**
- * ioat2_chan_watchdog - watch for stuck channels
- */
-static void ioat2_chan_watchdog(struct work_struct *work)
-{
-	struct ioatdma_device *device =
-		container_of(work, struct ioatdma_device, work.work);
-	struct ioat2_dma_chan *ioat;
-	struct ioat_chan_common *chan;
-	u16 active;
-	int i;
-
-	dev_dbg(&device->pdev->dev, "%s\n", __func__);
-
-	for (i = 0; i < device->common.chancnt; i++) {
-		chan = ioat_chan_by_index(device, i);
-		ioat = container_of(chan, struct ioat2_dma_chan, base);
-
-		/*
-		 * for version 2.0 if there are descriptors yet to be processed
-		 * and the last completed hasn't changed since the last watchdog
-		 *      if they haven't hit the pending level
-		 *          issue the pending to push them through
-		 *      else
-		 *          try resetting the channel
-		 */
-		spin_lock_bh(&ioat->ring_lock);
-		active = ioat2_ring_active(ioat);
-		spin_unlock_bh(&ioat->ring_lock);
-
-		if (active &&
-		    chan->last_completion &&
-		    chan->last_completion == chan->watchdog_completion) {
-
-			if (ioat->pending == 1)
-				ioat2_issue_pending(&chan->common);
-			else {
-				ioat2_reset_channel(ioat);
-				chan->watchdog_completion = 0;
-			}
-		} else {
-			chan->last_compl_desc_addr_hw = 0;
-			chan->watchdog_completion = chan->last_completion;
-		}
-		chan->watchdog_last_tcp_cookie = chan->watchdog_tcp_cookie;
-	}
-	schedule_delayed_work(&device->work, WATCHDOG_DELAY);
-}
-
-/**
- * ioat2_cleanup - clean finished descriptors (advance tail pointer)
- * @chan: ioat channel to be cleaned up
- */
-static void ioat2_cleanup(struct ioat2_dma_chan *ioat)
-{
-	struct ioat_chan_common *chan = &ioat->base;
-	unsigned long phys_complete;
+	struct dma_async_tx_descriptor *tx;
 	struct ioat_ring_ent *desc;
 	bool seen_current = false;
 	u16 active;
 	int i;
-	struct dma_async_tx_descriptor *tx;
-
-	prefetch(chan->completion);
-
-	spin_lock_bh(&chan->cleanup_lock);
-	phys_complete = ioat_get_current_completion(chan);
-	if (phys_complete == chan->last_completion) {
-		spin_unlock_bh(&chan->cleanup_lock);
-		/*
-		 * perhaps we're stuck so hard that the watchdog can't go off?
-		 * try to catch it after WATCHDOG_DELAY seconds
-		 */
-		if (chan->device->version < IOAT_VER_3_0) {
-			unsigned long tmo;
-
-			tmo = chan->last_completion_time + HZ*WATCHDOG_DELAY;
-			if (time_after(jiffies, tmo)) {
-				ioat2_chan_watchdog(&(chan->device->work.work));
-				chan->last_completion_time = jiffies;
-			}
-		}
-		return;
-	}
-	chan->last_completion_time = jiffies;
-
-	spin_lock_bh(&ioat->ring_lock);
 
 	dev_dbg(to_dev(chan), "%s: head: %#x tail: %#x issued: %#x\n",
 		__func__, ioat->head, ioat->tail, ioat->issued);
@@ -329,10 +162,42 @@ static void ioat2_cleanup(struct ioat2_dma_chan *ioat)
 	}
 	ioat->tail += i;
 	BUG_ON(!seen_current); /* no active descs have written a completion? */
-	spin_unlock_bh(&ioat->ring_lock);
 
 	chan->last_completion = phys_complete;
+	if (ioat->head == ioat->tail) {
+		dev_dbg(to_dev(chan), "%s: cancel completion timeout\n",
+			__func__);
+		clear_bit(IOAT_COMPLETION_PENDING, &chan->state);
+	}
+}
+
+/**
+ * ioat2_cleanup - clean finished descriptors (advance tail pointer)
+ * @chan: ioat channel to be cleaned up
+ */
+static void ioat2_cleanup(struct ioat2_dma_chan *ioat)
+{
+	struct ioat_chan_common *chan = &ioat->base;
+	unsigned long phys_complete;
 
+	prefetch(chan->completion);
+
+	if (!spin_trylock_bh(&chan->cleanup_lock))
+		return;
+
+	if (!ioat_cleanup_preamble(chan, &phys_complete)) {
+		spin_unlock_bh(&chan->cleanup_lock);
+		return;
+	}
+
+	if (!spin_trylock_bh(&ioat->ring_lock)) {
+		spin_unlock_bh(&chan->cleanup_lock);
+		return;
+	}
+
+	__cleanup(ioat, phys_complete);
+
+	spin_unlock_bh(&ioat->ring_lock);
 	spin_unlock_bh(&chan->cleanup_lock);
 }
 
@@ -344,6 +209,90 @@ static void ioat2_cleanup_tasklet(unsigned long data)
 	writew(IOAT_CHANCTRL_RUN, ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
 }
 
+static void __restart_chan(struct ioat2_dma_chan *ioat)
+{
+	struct ioat_chan_common *chan = &ioat->base;
+
+	/* set the tail to be re-issued */
+	ioat->issued = ioat->tail;
+	ioat->dmacount = 0;
+	set_bit(IOAT_COMPLETION_PENDING, &chan->state);
+	mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+
+	dev_dbg(to_dev(chan),
+		"%s: head: %#x tail: %#x issued: %#x count: %#x\n",
+		__func__, ioat->head, ioat->tail, ioat->issued, ioat->dmacount);
+
+	if (ioat2_ring_pending(ioat)) {
+		struct ioat_ring_ent *desc;
+
+		desc = ioat2_get_ring_ent(ioat, ioat->tail);
+		ioat2_set_chainaddr(ioat, desc->txd.phys);
+		__ioat2_issue_pending(ioat);
+	} else
+		__ioat2_start_null_desc(ioat);
+}
+
+static void ioat2_restart_channel(struct ioat2_dma_chan *ioat)
+{
+	struct ioat_chan_common *chan = &ioat->base;
+	unsigned long phys_complete;
+	u32 status;
+
+	status = ioat_chansts(chan);
+	if (is_ioat_active(status) || is_ioat_idle(status))
+		ioat_suspend(chan);
+	while (is_ioat_active(status) || is_ioat_idle(status)) {
+		status = ioat_chansts(chan);
+		cpu_relax();
+	}
+
+	if (ioat_cleanup_preamble(chan, &phys_complete))
+		__cleanup(ioat, phys_complete);
+
+	__restart_chan(ioat);
+}
+
+static void ioat2_timer_event(unsigned long data)
+{
+	struct ioat2_dma_chan *ioat = (void *) data;
+	struct ioat_chan_common *chan = &ioat->base;
+
+	spin_lock_bh(&chan->cleanup_lock);
+	if (test_bit(IOAT_COMPLETION_PENDING, &chan->state)) {
+		unsigned long phys_complete;
+		u64 status;
+
+		spin_lock_bh(&ioat->ring_lock);
+		status = ioat_chansts(chan);
+
+		/* when halted due to errors check for channel
+		 * programming errors before advancing the completion state
+		 */
+		if (is_ioat_halted(status)) {
+			u32 chanerr;
+
+			chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
+			BUG_ON(is_ioat_bug(chanerr));
+		}
+
+		/* if we haven't made progress and we have already
+		 * acknowledged a pending completion once, then be more
+		 * forceful with a restart
+		 */
+		if (ioat_cleanup_preamble(chan, &phys_complete))
+			__cleanup(ioat, phys_complete);
+		else if (test_bit(IOAT_COMPLETION_ACK, &chan->state))
+			ioat2_restart_channel(ioat);
+		else {
+			set_bit(IOAT_COMPLETION_ACK, &chan->state);
+			mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+		}
+		spin_unlock_bh(&ioat->ring_lock);
+	}
+	spin_unlock_bh(&chan->cleanup_lock);
+}
+
 /**
  * ioat2_enumerate_channels - find and initialize the device's channels
  * @device: the device to be enumerated
@@ -381,7 +330,7 @@ static int ioat2_enumerate_channels(struct ioatdma_device *device)
 			break;
 
 		ioat_init_channel(device, &ioat->base, i,
-				  ioat2_reset_part2,
+				  ioat2_timer_event,
 				  ioat2_cleanup_tasklet,
 				  (unsigned long) ioat);
 		ioat->xfercap_log = xfercap_log;
@@ -395,6 +344,7 @@ static dma_cookie_t ioat2_tx_submit_unlock(struct dma_async_tx_descriptor *tx)
 {
 	struct dma_chan *c = tx->chan;
 	struct ioat2_dma_chan *ioat = to_ioat2_chan(c);
+	struct ioat_chan_common *chan = &ioat->base;
 	dma_cookie_t cookie = c->cookie;
 
 	cookie++;
@@ -404,6 +354,8 @@ static dma_cookie_t ioat2_tx_submit_unlock(struct dma_async_tx_descriptor *tx)
 	c->cookie = cookie;
 	dev_dbg(to_dev(&ioat->base), "%s: cookie: %d\n", __func__, cookie);
 
+	if (!test_and_set_bit(IOAT_COMPLETION_PENDING, &chan->state))
+		mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
 	ioat2_update_pending(ioat);
 	spin_unlock_bh(&ioat->ring_lock);
 
@@ -543,9 +495,18 @@ static int ioat2_alloc_and_lock(u16 *idx, struct ioat2_dma_chan *ioat, int num_d
 				ioat->issued);
 		spin_unlock_bh(&ioat->ring_lock);
 
-		/* do direct reclaim in the allocation failure case */
-		ioat2_cleanup(ioat);
-
+		/* progress reclaim in the allocation failure case we
+		 * may be called under bh_disabled so we need to trigger
+		 * the timer event directly
+		 */
+		spin_lock_bh(&chan->cleanup_lock);
+		if (jiffies > chan->timer.expires &&
+		    timer_pending(&chan->timer)) {
+			mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+			spin_unlock_bh(&chan->cleanup_lock);
+			ioat2_timer_event((unsigned long) ioat);
+		} else
+			spin_unlock_bh(&chan->cleanup_lock);
 		return -ENOMEM;
 	}
 
@@ -624,6 +585,7 @@ static void ioat2_free_chan_resources(struct dma_chan *c)
 		return;
 
 	tasklet_disable(&chan->cleanup_task);
+	del_timer_sync(&chan->timer);
 	ioat2_cleanup(ioat);
 
 	/* Delay 100ms after reset to allow internal DMA logic to quiesce
@@ -663,10 +625,6 @@ static void ioat2_free_chan_resources(struct dma_chan *c)
 	chan->completion_dma = 0;
 	ioat->pending = 0;
 	ioat->dmacount = 0;
-	chan->watchdog_completion = 0;
-	chan->last_compl_desc_addr_hw = 0;
-	chan->watchdog_tcp_cookie = 0;
-	chan->watchdog_last_tcp_cookie = 0;
 }
 
 static enum dma_status
@@ -716,9 +674,6 @@ int __devinit ioat2_dma_probe(struct ioatdma_device *device, int dca)
 	if (dca)
 		device->dca = ioat2_dca_init(pdev, device->reg_base);
 
-	INIT_DELAYED_WORK(&device->work, ioat2_chan_watchdog);
-	schedule_delayed_work(&device->work, WATCHDOG_DELAY);
-
 	return err;
 }