ntb: no sleep in ntb_async_tx_submit

Do not sleep in ntb_async_tx_submit, which could deadlock.
This reverts commit "8c874cc140d667f84ae4642bb5b5e0d6396d2ca4"

Fixes: 8c874cc140 ("NTB: Address out of DMA descriptor issue with NTB")
Reported-by: Jia-Ju Bai <baijiaju1990@163.com>
Signed-off-by: Allen Hubbe <Allen.Hubbe@dell.com>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

drivers/ntb/ntb_transport.c

@@ -177,14 +177,12 @@ struct ntb_transport_qp {
 	u64 rx_err_ver;
 	u64 rx_memcpy;
 	u64 rx_async;
-	u64 dma_rx_prep_err;
 	u64 tx_bytes;
 	u64 tx_pkts;
 	u64 tx_ring_full;
 	u64 tx_err_no_buf;
 	u64 tx_memcpy;
 	u64 tx_async;
-	u64 dma_tx_prep_err;
 };
 
 struct ntb_transport_mw {
@@ -254,8 +252,6 @@ enum {
 #define QP_TO_MW(nt, qp)	((qp) % nt->mw_count)
 #define NTB_QP_DEF_NUM_ENTRIES	100
 #define NTB_LINK_DOWN_TIMEOUT	10
-#define DMA_RETRIES		20
-#define DMA_OUT_RESOURCE_TO	msecs_to_jiffies(50)
 
 static void ntb_transport_rxc_db(unsigned long data);
 static const struct ntb_ctx_ops ntb_transport_ops;
@@ -516,12 +512,6 @@ static ssize_t debugfs_read(struct file *filp, char __user *ubuf, size_t count,
 	out_offset += snprintf(buf + out_offset, out_count - out_offset,
 			       "free tx - \t%u\n",
 			       ntb_transport_tx_free_entry(qp));
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
-			       "DMA tx prep err - \t%llu\n",
-			       qp->dma_tx_prep_err);
-	out_offset += snprintf(buf + out_offset, out_count - out_offset,
-			       "DMA rx prep err - \t%llu\n",
-			       qp->dma_rx_prep_err);
 
 	out_offset += snprintf(buf + out_offset, out_count - out_offset,
 			       "\n");
@@ -768,8 +758,6 @@ static void ntb_qp_link_down_reset(struct ntb_transport_qp *qp)
 	qp->tx_err_no_buf = 0;
 	qp->tx_memcpy = 0;
 	qp->tx_async = 0;
-	qp->dma_tx_prep_err = 0;
-	qp->dma_rx_prep_err = 0;
 }
 
 static void ntb_qp_link_cleanup(struct ntb_transport_qp *qp)
@@ -1317,7 +1305,6 @@ static int ntb_async_rx_submit(struct ntb_queue_entry *entry, void *offset)
 	struct dmaengine_unmap_data *unmap;
 	dma_cookie_t cookie;
 	void *buf = entry->buf;
-	int retries = 0;
 
 	len = entry->len;
 	device = chan->device;
@@ -1346,22 +1333,11 @@ static int ntb_async_rx_submit(struct ntb_queue_entry *entry, void *offset)
 
 	unmap->from_cnt = 1;
 
-	for (retries = 0; retries < DMA_RETRIES; retries++) {
-		txd = device->device_prep_dma_memcpy(chan,
-						     unmap->addr[1],
-						     unmap->addr[0], len,
-						     DMA_PREP_INTERRUPT);
-		if (txd)
-			break;
-
-		set_current_state(TASK_INTERRUPTIBLE);
-		schedule_timeout(DMA_OUT_RESOURCE_TO);
-	}
-
-	if (!txd) {
-		qp->dma_rx_prep_err++;
+	txd = device->device_prep_dma_memcpy(chan, unmap->addr[1],
+					     unmap->addr[0], len,
+					     DMA_PREP_INTERRUPT);
+	if (!txd)
 		goto err_get_unmap;
-	}
 
 	txd->callback_result = ntb_rx_copy_callback;
 	txd->callback_param = entry;
@@ -1606,7 +1582,6 @@ static int ntb_async_tx_submit(struct ntb_transport_qp *qp,
 	struct dmaengine_unmap_data *unmap;
 	dma_addr_t dest;
 	dma_cookie_t cookie;
-	int retries = 0;
 
 	device = chan->device;
 	dest = qp->tx_mw_phys + qp->tx_max_frame * entry->tx_index;
@@ -1628,21 +1603,10 @@ static int ntb_async_tx_submit(struct ntb_transport_qp *qp,
 
 	unmap->to_cnt = 1;
 
-	for (retries = 0; retries < DMA_RETRIES; retries++) {
-		txd = device->device_prep_dma_memcpy(chan, dest,
-						     unmap->addr[0], len,
-						     DMA_PREP_INTERRUPT);
-		if (txd)
-			break;
-
-		set_current_state(TASK_INTERRUPTIBLE);
-		schedule_timeout(DMA_OUT_RESOURCE_TO);
-	}
-
-	if (!txd) {
-		qp->dma_tx_prep_err++;
+	txd = device->device_prep_dma_memcpy(chan, dest, unmap->addr[0], len,
+					     DMA_PREP_INTERRUPT);
+	if (!txd)
 		goto err_get_unmap;
-	}
 
 	txd->callback_result = ntb_tx_copy_callback;
 	txd->callback_param = entry;