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>

drivers/dma/ioat/dma.h

@@ -23,6 +23,7 @@
 
 #include <linux/dmaengine.h>
 #include "hw.h"
+#include "registers.h"
 #include <linux/init.h>
 #include <linux/dmapool.h>
 #include <linux/cache.h>
@@ -33,7 +34,6 @@
 
 #define IOAT_LOW_COMPLETION_MASK	0xffffffc0
 #define IOAT_DMA_DCA_ANY_CPU		~0
-#define IOAT_WATCHDOG_PERIOD		(2 * HZ)
 
 #define to_ioatdma_device(dev) container_of(dev, struct ioatdma_device, common)
 #define to_ioat_desc(lh) container_of(lh, struct ioat_desc_sw, node)
@@ -42,9 +42,6 @@
 
 #define chan_num(ch) ((int)((ch)->reg_base - (ch)->device->reg_base) / 0x80)
 
-#define RESET_DELAY  msecs_to_jiffies(100)
-#define WATCHDOG_DELAY  round_jiffies(msecs_to_jiffies(2000))
-
 /*
  * workaround for IOAT ver.3.0 null descriptor issue
  * (channel returns error when size is 0)
@@ -72,7 +69,6 @@ struct ioatdma_device {
 	struct pci_pool *completion_pool;
 	struct dma_device common;
 	u8 version;
-	struct delayed_work work;
 	struct msix_entry msix_entries[4];
 	struct ioat_chan_common *idx[4];
 	struct dca_provider *dca;
@@ -81,24 +77,21 @@ struct ioatdma_device {
 };
 
 struct ioat_chan_common {
+	struct dma_chan common;
 	void __iomem *reg_base;
-
 	unsigned long last_completion;
-	unsigned long last_completion_time;
-
 	spinlock_t cleanup_lock;
 	dma_cookie_t completed_cookie;
-	unsigned long watchdog_completion;
-	int watchdog_tcp_cookie;
-	u32 watchdog_last_tcp_cookie;
-	struct delayed_work work;
-
+	unsigned long state;
+	#define IOAT_COMPLETION_PENDING 0
+	#define IOAT_COMPLETION_ACK 1
+	#define IOAT_RESET_PENDING 2
+	struct timer_list timer;
+	#define COMPLETION_TIMEOUT msecs_to_jiffies(100)
+	#define RESET_DELAY msecs_to_jiffies(100)
 	struct ioatdma_device *device;
-	struct dma_chan common;
-
 	dma_addr_t completion_dma;
 	u64 *completion;
-	unsigned long last_compl_desc_addr_hw;
 	struct tasklet_struct cleanup_task;
 };
 
@@ -148,7 +141,6 @@ ioat_is_complete(struct dma_chan *c, dma_cookie_t cookie,
 
 	last_used = c->cookie;
 	last_complete = chan->completed_cookie;
-	chan->watchdog_tcp_cookie = cookie;
 
 	if (done)
 		*done = last_complete;
@@ -215,6 +207,85 @@ ioat_chan_by_index(struct ioatdma_device *device, int index)
 	return device->idx[index];
 }
 
+static inline u64 ioat_chansts(struct ioat_chan_common *chan)
+{
+	u8 ver = chan->device->version;
+	u64 status;
+	u32 status_lo;
+
+	/* We need to read the low address first as this causes the
+	 * chipset to latch the upper bits for the subsequent read
+	 */
+	status_lo = readl(chan->reg_base + IOAT_CHANSTS_OFFSET_LOW(ver));
+	status = readl(chan->reg_base + IOAT_CHANSTS_OFFSET_HIGH(ver));
+	status <<= 32;
+	status |= status_lo;
+
+	return status;
+}
+
+static inline void ioat_start(struct ioat_chan_common *chan)
+{
+	u8 ver = chan->device->version;
+
+	writeb(IOAT_CHANCMD_START, chan->reg_base + IOAT_CHANCMD_OFFSET(ver));
+}
+
+static inline u64 ioat_chansts_to_addr(u64 status)
+{
+	return status & IOAT_CHANSTS_COMPLETED_DESCRIPTOR_ADDR;
+}
+
+static inline u32 ioat_chanerr(struct ioat_chan_common *chan)
+{
+	return readl(chan->reg_base + IOAT_CHANERR_OFFSET);
+}
+
+static inline void ioat_suspend(struct ioat_chan_common *chan)
+{
+	u8 ver = chan->device->version;
+
+	writeb(IOAT_CHANCMD_SUSPEND, chan->reg_base + IOAT_CHANCMD_OFFSET(ver));
+}
+
+static inline void ioat_set_chainaddr(struct ioat_dma_chan *ioat, u64 addr)
+{
+	struct ioat_chan_common *chan = &ioat->base;
+
+	writel(addr & 0x00000000FFFFFFFF,
+	       chan->reg_base + IOAT1_CHAINADDR_OFFSET_LOW);
+	writel(addr >> 32,
+	       chan->reg_base + IOAT1_CHAINADDR_OFFSET_HIGH);
+}
+
+static inline bool is_ioat_active(unsigned long status)
+{
+	return ((status & IOAT_CHANSTS_STATUS) == IOAT_CHANSTS_ACTIVE);
+}
+
+static inline bool is_ioat_idle(unsigned long status)
+{
+	return ((status & IOAT_CHANSTS_STATUS) == IOAT_CHANSTS_DONE);
+}
+
+static inline bool is_ioat_halted(unsigned long status)
+{
+	return ((status & IOAT_CHANSTS_STATUS) == IOAT_CHANSTS_HALTED);
+}
+
+static inline bool is_ioat_suspended(unsigned long status)
+{
+	return ((status & IOAT_CHANSTS_STATUS) == IOAT_CHANSTS_SUSPENDED);
+}
+
+/* channel was fatally programmed */
+static inline bool is_ioat_bug(unsigned long err)
+{
+	return !!(err & (IOAT_CHANERR_SRC_ADDR_ERR|IOAT_CHANERR_DEST_ADDR_ERR|
+			 IOAT_CHANERR_NEXT_ADDR_ERR|IOAT_CHANERR_CONTROL_ERR|
+			 IOAT_CHANERR_LENGTH_ERR));
+}
+
 int __devinit ioat_probe(struct ioatdma_device *device);
 int __devinit ioat_register(struct ioatdma_device *device);
 int __devinit ioat1_dma_probe(struct ioatdma_device *dev, int dca);
@@ -224,8 +295,11 @@ struct dca_provider * __devinit ioat_dca_init(struct pci_dev *pdev,
 unsigned long ioat_get_current_completion(struct ioat_chan_common *chan);
 void ioat_init_channel(struct ioatdma_device *device,
 		       struct ioat_chan_common *chan, int idx,
-		       work_func_t work_fn, void (*tasklet)(unsigned long),
-		       unsigned long tasklet_data);
+		       void (*timer_fn)(unsigned long),
+		       void (*tasklet)(unsigned long),
+		       unsigned long ioat);
 void ioat_dma_unmap(struct ioat_chan_common *chan, enum dma_ctrl_flags flags,
 		    size_t len, struct ioat_dma_descriptor *hw);
+bool ioat_cleanup_preamble(struct ioat_chan_common *chan,
+			   unsigned long *phys_complete);
 #endif /* IOATDMA_H */

drivers/dma/ioat/dma_v2.h

@@ -127,6 +127,16 @@ ioat2_get_ring_ent(struct ioat2_dma_chan *ioat, u16 idx)
 	return ioat->ring[idx & ioat2_ring_mask(ioat)];
 }
 
+static inline void ioat2_set_chainaddr(struct ioat2_dma_chan *ioat, u64 addr)
+{
+	struct ioat_chan_common *chan = &ioat->base;
+
+	writel(addr & 0x00000000FFFFFFFF,
+	       chan->reg_base + IOAT2_CHAINADDR_OFFSET_LOW);
+	writel(addr >> 32,
+	       chan->reg_base + IOAT2_CHAINADDR_OFFSET_HIGH);
+}
+
 int __devinit ioat2_dma_probe(struct ioatdma_device *dev, int dca);
 int __devinit ioat3_dma_probe(struct ioatdma_device *dev, int dca);
 struct dca_provider * __devinit ioat2_dca_init(struct pci_dev *pdev, void __iomem *iobase);

drivers/dma/ioat/registers.h

@@ -101,11 +101,11 @@
 #define IOAT_CHANSTS_COMPLETED_DESCRIPTOR_ADDR	(~0x3fULL)
 #define IOAT_CHANSTS_SOFT_ERR			0x10ULL
 #define IOAT_CHANSTS_UNAFFILIATED_ERR		0x8ULL
-#define IOAT_CHANSTS_DMA_TRANSFER_STATUS	0x7ULL
-#define IOAT_CHANSTS_DMA_TRANSFER_STATUS_ACTIVE	0x0
-#define IOAT_CHANSTS_DMA_TRANSFER_STATUS_DONE	0x1
-#define IOAT_CHANSTS_DMA_TRANSFER_STATUS_SUSPENDED	0x2
-#define IOAT_CHANSTS_DMA_TRANSFER_STATUS_HALTED	0x3
+#define IOAT_CHANSTS_STATUS	0x7ULL
+#define IOAT_CHANSTS_ACTIVE	0x0
+#define IOAT_CHANSTS_DONE	0x1
+#define IOAT_CHANSTS_SUSPENDED	0x2
+#define IOAT_CHANSTS_HALTED	0x3
 
 
 
@@ -208,18 +208,18 @@
 #define IOAT_CDAR_OFFSET_HIGH			0x24
 
 #define IOAT_CHANERR_OFFSET			0x28	/* 32-bit Channel Error Register */
-#define IOAT_CHANERR_DMA_TRANSFER_SRC_ADDR_ERR	0x0001
-#define IOAT_CHANERR_DMA_TRANSFER_DEST_ADDR_ERR	0x0002
-#define IOAT_CHANERR_NEXT_DESCRIPTOR_ADDR_ERR	0x0004
-#define IOAT_CHANERR_NEXT_DESCRIPTOR_ALIGNMENT_ERR	0x0008
+#define IOAT_CHANERR_SRC_ADDR_ERR	0x0001
+#define IOAT_CHANERR_DEST_ADDR_ERR	0x0002
+#define IOAT_CHANERR_NEXT_ADDR_ERR	0x0004
+#define IOAT_CHANERR_NEXT_DESC_ALIGN_ERR	0x0008
 #define IOAT_CHANERR_CHAIN_ADDR_VALUE_ERR	0x0010
 #define IOAT_CHANERR_CHANCMD_ERR		0x0020
 #define IOAT_CHANERR_CHIPSET_UNCORRECTABLE_DATA_INTEGRITY_ERR	0x0040
 #define IOAT_CHANERR_DMA_UNCORRECTABLE_DATA_INTEGRITY_ERR	0x0080
 #define IOAT_CHANERR_READ_DATA_ERR		0x0100
 #define IOAT_CHANERR_WRITE_DATA_ERR		0x0200
-#define IOAT_CHANERR_DESCRIPTOR_CONTROL_ERR	0x0400
-#define IOAT_CHANERR_DESCRIPTOR_LENGTH_ERR	0x0800
+#define IOAT_CHANERR_CONTROL_ERR	0x0400
+#define IOAT_CHANERR_LENGTH_ERR	0x0800
 #define IOAT_CHANERR_COMPLETION_ADDR_ERR	0x1000
 #define IOAT_CHANERR_INT_CONFIGURATION_ERR	0x2000
 #define IOAT_CHANERR_SOFT_ERR			0x4000

drivers/idle/i7300_idle.c

@@ -126,9 +126,9 @@ static void i7300_idle_ioat_stop(void)
 		udelay(10);
 
 		sts = readq(ioat_chanbase + IOAT1_CHANSTS_OFFSET) &
-			IOAT_CHANSTS_DMA_TRANSFER_STATUS;
+			IOAT_CHANSTS_STATUS;
 
-		if (sts != IOAT_CHANSTS_DMA_TRANSFER_STATUS_ACTIVE)
+		if (sts != IOAT_CHANSTS_ACTIVE)
 			break;
 
 	}
@@ -160,9 +160,9 @@ static int __init i7300_idle_ioat_selftest(u8 *ctl,
 	udelay(1000);
 
 	chan_sts = readq(ioat_chanbase + IOAT1_CHANSTS_OFFSET) &
-			IOAT_CHANSTS_DMA_TRANSFER_STATUS;
+			IOAT_CHANSTS_STATUS;
 
-	if (chan_sts != IOAT_CHANSTS_DMA_TRANSFER_STATUS_DONE) {
+	if (chan_sts != IOAT_CHANSTS_DONE) {
 		/* Not complete, reset the channel */
 		writeb(IOAT_CHANCMD_RESET,
 		       ioat_chanbase + IOAT1_CHANCMD_OFFSET);
@@ -288,9 +288,9 @@ static void __exit i7300_idle_ioat_exit(void)
 		       ioat_chanbase + IOAT1_CHANCMD_OFFSET);
 
 		chan_sts = readq(ioat_chanbase + IOAT1_CHANSTS_OFFSET) &
-			IOAT_CHANSTS_DMA_TRANSFER_STATUS;
+			IOAT_CHANSTS_STATUS;
 
-		if (chan_sts != IOAT_CHANSTS_DMA_TRANSFER_STATUS_ACTIVE) {
+		if (chan_sts != IOAT_CHANSTS_ACTIVE) {
 			writew(0, ioat_chanbase + IOAT_CHANCTRL_OFFSET);
 			break;
 		}
@@ -298,14 +298,14 @@ static void __exit i7300_idle_ioat_exit(void)
 	}
 
 	chan_sts = readq(ioat_chanbase + IOAT1_CHANSTS_OFFSET) &
-			IOAT_CHANSTS_DMA_TRANSFER_STATUS;
+			IOAT_CHANSTS_STATUS;
 
 	/*
 	 * We tried to reset multiple times. If IO A/T channel is still active
 	 * flag an error and return without cleanup. Memory leak is better
 	 * than random corruption in that extreme error situation.
 	 */
-	if (chan_sts == IOAT_CHANSTS_DMA_TRANSFER_STATUS_ACTIVE) {
+	if (chan_sts == IOAT_CHANSTS_ACTIVE) {
 		printk(KERN_ERR I7300_PRINT "Unable to stop IO A/T channels."
 			" Not freeing resources\n");
 		return;