IB/ipath: User mode send DMA

A new file which allows the IBA7220 send DMA engine to be used from
userland.  The routines here are not linked in yet, that will happen in
a follow-on patch...
Signed-off-by: Arthur Jones <arthur.jones@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_user_sdma.c

+/*
+ * Copyright (c) 2007, 2008 QLogic Corporation. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include <linux/mm.h>
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/dmapool.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/highmem.h>
+#include <linux/io.h>
+#include <linux/uio.h>
+#include <linux/rbtree.h>
+#include <linux/spinlock.h>
+#include <linux/delay.h>
+
+#include "ipath_kernel.h"
+#include "ipath_user_sdma.h"
+
+/* minimum size of header */
+#define IPATH_USER_SDMA_MIN_HEADER_LENGTH	64
+/* expected size of headers (for dma_pool) */
+#define IPATH_USER_SDMA_EXP_HEADER_LENGTH	64
+/* length mask in PBC (lower 11 bits) */
+#define IPATH_PBC_LENGTH_MASK			((1 << 11) - 1)
+
+struct ipath_user_sdma_pkt {
+	u8 naddr;		/* dimension of addr (1..3) ... */
+	u32 counter;		/* sdma pkts queued counter for this entry */
+	u64 added;		/* global descq number of entries */
+
+	struct {
+		u32 offset;			/* offset for kvaddr, addr */
+		u32 length;			/* length in page */
+		u8  put_page;			/* should we put_page? */
+		u8  dma_mapped;			/* is page dma_mapped? */
+		struct page *page;		/* may be NULL (coherent mem) */
+		void *kvaddr;			/* FIXME: only for pio hack */
+		dma_addr_t addr;
+	} addr[4];   /* max pages, any more and we coalesce */
+	struct list_head list;	/* list element */
+};
+
+struct ipath_user_sdma_queue {
+	/*
+	 * pkts sent to dma engine are queued on this
+	 * list head.  the type of the elements of this
+	 * list are struct ipath_user_sdma_pkt...
+	 */
+	struct list_head sent;
+
+	/* headers with expected length are allocated from here... */
+	char header_cache_name[64];
+	struct dma_pool *header_cache;
+
+	/* packets are allocated from the slab cache... */
+	char pkt_slab_name[64];
+	struct kmem_cache *pkt_slab;
+
+	/* as packets go on the queued queue, they are counted... */
+	u32 counter;
+	u32 sent_counter;
+
+	/* dma page table */
+	struct rb_root dma_pages_root;
+
+	/* protect everything above... */
+	struct mutex lock;
+};
+
+struct ipath_user_sdma_queue *
+ipath_user_sdma_queue_create(struct device *dev, int unit, int port, int sport)
+{
+	struct ipath_user_sdma_queue *pq =
+		kmalloc(sizeof(struct ipath_user_sdma_queue), GFP_KERNEL);
+
+	if (!pq)
+		goto done;
+
+	pq->counter = 0;
+	pq->sent_counter = 0;
+	INIT_LIST_HEAD(&pq->sent);
+
+	mutex_init(&pq->lock);
+
+	snprintf(pq->pkt_slab_name, sizeof(pq->pkt_slab_name),
+		 "ipath-user-sdma-pkts-%u-%02u.%02u", unit, port, sport);
+	pq->pkt_slab = kmem_cache_create(pq->pkt_slab_name,
+					 sizeof(struct ipath_user_sdma_pkt),
+					 0, 0, NULL);
+
+	if (!pq->pkt_slab)
+		goto err_kfree;
+
+	snprintf(pq->header_cache_name, sizeof(pq->header_cache_name),
+		 "ipath-user-sdma-headers-%u-%02u.%02u", unit, port, sport);
+	pq->header_cache = dma_pool_create(pq->header_cache_name,
+					   dev,
+					   IPATH_USER_SDMA_EXP_HEADER_LENGTH,
+					   4, 0);
+	if (!pq->header_cache)
+		goto err_slab;
+
+	pq->dma_pages_root = RB_ROOT;
+
+	goto done;
+
+err_slab:
+	kmem_cache_destroy(pq->pkt_slab);
+err_kfree:
+	kfree(pq);
+	pq = NULL;
+
+done:
+	return pq;
+}
+
+static void ipath_user_sdma_init_frag(struct ipath_user_sdma_pkt *pkt,
+				      int i, size_t offset, size_t len,
+				      int put_page, int dma_mapped,
+				      struct page *page,
+				      void *kvaddr, dma_addr_t dma_addr)
+{
+	pkt->addr[i].offset = offset;
+	pkt->addr[i].length = len;
+	pkt->addr[i].put_page = put_page;
+	pkt->addr[i].dma_mapped = dma_mapped;
+	pkt->addr[i].page = page;
+	pkt->addr[i].kvaddr = kvaddr;
+	pkt->addr[i].addr = dma_addr;
+}
+
+static void ipath_user_sdma_init_header(struct ipath_user_sdma_pkt *pkt,
+					u32 counter, size_t offset,
+					size_t len, int dma_mapped,
+					struct page *page,
+					void *kvaddr, dma_addr_t dma_addr)
+{
+	pkt->naddr = 1;
+	pkt->counter = counter;
+	ipath_user_sdma_init_frag(pkt, 0, offset, len, 0, dma_mapped, page,
+				  kvaddr, dma_addr);
+}
+
+/* we've too many pages in the iovec, coalesce to a single page */
+static int ipath_user_sdma_coalesce(const struct ipath_devdata *dd,
+				    struct ipath_user_sdma_pkt *pkt,
+				    const struct iovec *iov,
+				    unsigned long niov) {
+	int ret = 0;
+	struct page *page = alloc_page(GFP_KERNEL);
+	void *mpage_save;
+	char *mpage;
+	int i;
+	int len = 0;
+	dma_addr_t dma_addr;
+
+	if (!page) {
+		ret = -ENOMEM;
+		goto done;
+	}
+
+	mpage = kmap(page);
+	mpage_save = mpage;
+	for (i = 0; i < niov; i++) {
+		int cfur;
+
+		cfur = copy_from_user(mpage,
+				      iov[i].iov_base, iov[i].iov_len);
+		if (cfur) {
+			ret = -EFAULT;
+			goto free_unmap;
+		}
+
+		mpage += iov[i].iov_len;
+		len += iov[i].iov_len;
+	}
+
+	dma_addr = dma_map_page(&dd->pcidev->dev, page, 0, len,
+				DMA_TO_DEVICE);
+	if (dma_mapping_error(dma_addr)) {
+		ret = -ENOMEM;
+		goto free_unmap;
+	}
+
+	ipath_user_sdma_init_frag(pkt, 1, 0, len, 0, 1, page, mpage_save,
+				  dma_addr);
+	pkt->naddr = 2;
+
+	goto done;
+
+free_unmap:
+	kunmap(page);
+	__free_page(page);
+done:
+	return ret;
+}
+
+/* how many pages in this iovec element? */
+static int ipath_user_sdma_num_pages(const struct iovec *iov)
+{
+	const unsigned long addr  = (unsigned long) iov->iov_base;
+	const unsigned long  len  = iov->iov_len;
+	const unsigned long spage = addr & PAGE_MASK;
+	const unsigned long epage = (addr + len - 1) & PAGE_MASK;
+
+	return 1 + ((epage - spage) >> PAGE_SHIFT);
+}
+
+/* truncate length to page boundry */
+static int ipath_user_sdma_page_length(unsigned long addr, unsigned long len)
+{
+	const unsigned long offset = addr & ~PAGE_MASK;
+
+	return ((offset + len) > PAGE_SIZE) ? (PAGE_SIZE - offset) : len;
+}
+
+static void ipath_user_sdma_free_pkt_frag(struct device *dev,
+					  struct ipath_user_sdma_queue *pq,
+					  struct ipath_user_sdma_pkt *pkt,
+					  int frag)
+{
+	const int i = frag;
+
+	if (pkt->addr[i].page) {
+		if (pkt->addr[i].dma_mapped)
+			dma_unmap_page(dev,
+				       pkt->addr[i].addr,
+				       pkt->addr[i].length,
+				       DMA_TO_DEVICE);
+
+		if (pkt->addr[i].kvaddr)
+			kunmap(pkt->addr[i].page);
+
+		if (pkt->addr[i].put_page)
+			put_page(pkt->addr[i].page);
+		else
+			__free_page(pkt->addr[i].page);
+	} else if (pkt->addr[i].kvaddr)
+		/* free coherent mem from cache... */
+		dma_pool_free(pq->header_cache,
+			      pkt->addr[i].kvaddr, pkt->addr[i].addr);
+}
+
+/* return number of pages pinned... */
+static int ipath_user_sdma_pin_pages(const struct ipath_devdata *dd,
+				     struct ipath_user_sdma_pkt *pkt,
+				     unsigned long addr, int tlen, int npages)
+{
+	struct page *pages[2];
+	int j;
+	int ret;
+
+	ret = get_user_pages(current, current->mm, addr,
+			     npages, 0, 1, pages, NULL);
+
+	if (ret != npages) {
+		int i;
+
+		for (i = 0; i < ret; i++)
+			put_page(pages[i]);
+
+		ret = -ENOMEM;
+		goto done;
+	}
+
+	for (j = 0; j < npages; j++) {
+		/* map the pages... */
+		const int flen =
+			ipath_user_sdma_page_length(addr, tlen);
+		dma_addr_t dma_addr =
+			dma_map_page(&dd->pcidev->dev,
+				     pages[j], 0, flen, DMA_TO_DEVICE);
+		unsigned long fofs = addr & ~PAGE_MASK;
+
+		if (dma_mapping_error(dma_addr)) {
+			ret = -ENOMEM;
+			goto done;
+		}
+
+		ipath_user_sdma_init_frag(pkt, pkt->naddr, fofs, flen, 1, 1,
+					  pages[j], kmap(pages[j]),
+					  dma_addr);
+
+		pkt->naddr++;
+		addr += flen;
+		tlen -= flen;
+	}
+
+done:
+	return ret;
+}
+
+static int ipath_user_sdma_pin_pkt(const struct ipath_devdata *dd,
+				   struct ipath_user_sdma_queue *pq,
+				   struct ipath_user_sdma_pkt *pkt,
+				   const struct iovec *iov,
+				   unsigned long niov)
+{
+	int ret = 0;
+	unsigned long idx;
+
+	for (idx = 0; idx < niov; idx++) {
+		const int npages = ipath_user_sdma_num_pages(iov + idx);
+		const unsigned long addr = (unsigned long) iov[idx].iov_base;
+
+		ret = ipath_user_sdma_pin_pages(dd, pkt,
+						addr, iov[idx].iov_len,
+						npages);
+		if (ret < 0)
+			goto free_pkt;
+	}
+
+	goto done;
+
+free_pkt:
+	for (idx = 0; idx < pkt->naddr; idx++)
+		ipath_user_sdma_free_pkt_frag(&dd->pcidev->dev, pq, pkt, idx);
+
+done:
+	return ret;
+}
+
+static int ipath_user_sdma_init_payload(const struct ipath_devdata *dd,
+					struct ipath_user_sdma_queue *pq,
+					struct ipath_user_sdma_pkt *pkt,
+					const struct iovec *iov,
+					unsigned long niov, int npages)
+{
+	int ret = 0;
+
+	if (npages >= ARRAY_SIZE(pkt->addr))
+		ret = ipath_user_sdma_coalesce(dd, pkt, iov, niov);
+	else
+		ret = ipath_user_sdma_pin_pkt(dd, pq, pkt, iov, niov);
+
+	return ret;
+}
+
+/* free a packet list -- return counter value of last packet */
+static void ipath_user_sdma_free_pkt_list(struct device *dev,
+					  struct ipath_user_sdma_queue *pq,
+					  struct list_head *list)
+{
+	struct ipath_user_sdma_pkt *pkt, *pkt_next;
+
+	list_for_each_entry_safe(pkt, pkt_next, list, list) {
+		int i;
+
+		for (i = 0; i < pkt->naddr; i++)
+			ipath_user_sdma_free_pkt_frag(dev, pq, pkt, i);
+
+		kmem_cache_free(pq->pkt_slab, pkt);
+	}
+}
+
+/*
+ * copy headers, coalesce etc -- pq->lock must be held
+ *
+ * we queue all the packets to list, returning the
+ * number of bytes total.  list must be empty initially,
+ * as, if there is an error we clean it...
+ */
+static int ipath_user_sdma_queue_pkts(const struct ipath_devdata *dd,
+				      struct ipath_user_sdma_queue *pq,
+				      struct list_head *list,
+				      const struct iovec *iov,
+				      unsigned long niov,
+				      int maxpkts)
+{
+	unsigned long idx = 0;
+	int ret = 0;
+	int npkts = 0;
+	struct page *page = NULL;
+	__le32 *pbc;
+	dma_addr_t dma_addr;
+	struct ipath_user_sdma_pkt *pkt = NULL;
+	size_t len;
+	size_t nw;
+	u32 counter = pq->counter;
+	int dma_mapped = 0;
+
+	while (idx < niov && npkts < maxpkts) {
+		const unsigned long addr = (unsigned long) iov[idx].iov_base;
+		const unsigned long idx_save = idx;
+		unsigned pktnw;
+		unsigned pktnwc;
+		int nfrags = 0;
+		int npages = 0;
+		int cfur;
+
+		dma_mapped = 0;
+		len = iov[idx].iov_len;
+		nw = len >> 2;
+		page = NULL;
+
+		pkt = kmem_cache_alloc(pq->pkt_slab, GFP_KERNEL);
+		if (!pkt) {
+			ret = -ENOMEM;
+			goto free_list;
+		}
+
+		if (len < IPATH_USER_SDMA_MIN_HEADER_LENGTH ||
+		    len > PAGE_SIZE || len & 3 || addr & 3) {
+			ret = -EINVAL;
+			goto free_pkt;
+		}
+
+		if (len == IPATH_USER_SDMA_EXP_HEADER_LENGTH)
+			pbc = dma_pool_alloc(pq->header_cache, GFP_KERNEL,
+					     &dma_addr);
+		else
+			pbc = NULL;
+
+		if (!pbc) {
+			page = alloc_page(GFP_KERNEL);
+			if (!page) {
+				ret = -ENOMEM;
+				goto free_pkt;
+			}
+			pbc = kmap(page);
+		}
+
+		cfur = copy_from_user(pbc, iov[idx].iov_base, len);
+		if (cfur) {
+			ret = -EFAULT;
+			goto free_pbc;
+		}
+
+		/*
+		 * this assignment is a bit strange.  it's because the
+		 * the pbc counts the number of 32 bit words in the full
+		 * packet _except_ the first word of the pbc itself...
+		 */
+		pktnwc = nw - 1;
+
+		/*
+		 * pktnw computation yields the number of 32 bit words
+		 * that the caller has indicated in the PBC.  note that
+		 * this is one less than the total number of words that
+		 * goes to the send DMA engine as the first 32 bit word
+		 * of the PBC itself is not counted.  Armed with this count,
+		 * we can verify that the packet is consistent with the
+		 * iovec lengths.
+		 */
+		pktnw = le32_to_cpu(*pbc) & IPATH_PBC_LENGTH_MASK;
+		if (pktnw < pktnwc || pktnw > pktnwc + (PAGE_SIZE >> 2)) {
+			ret = -EINVAL;
+			goto free_pbc;
+		}
+
+
+		idx++;
+		while (pktnwc < pktnw && idx < niov) {
+			const size_t slen = iov[idx].iov_len;
+			const unsigned long faddr =
+				(unsigned long) iov[idx].iov_base;
+
+			if (slen & 3 || faddr & 3 || !slen ||
+			    slen > PAGE_SIZE) {
+				ret = -EINVAL;
+				goto free_pbc;
+			}
+
+			npages++;
+			if ((faddr & PAGE_MASK) !=
+			    ((faddr + slen - 1) & PAGE_MASK))
+				npages++;
+
+			pktnwc += slen >> 2;
+			idx++;
+			nfrags++;
+		}
+
+		if (pktnwc != pktnw) {
+			ret = -EINVAL;
+			goto free_pbc;
+		}
+
+		if (page) {
+			dma_addr = dma_map_page(&dd->pcidev->dev,
+						page, 0, len, DMA_TO_DEVICE);
+			if (dma_mapping_error(dma_addr)) {
+				ret = -ENOMEM;
+				goto free_pbc;
+			}
+
+			dma_mapped = 1;
+		}
+
+		ipath_user_sdma_init_header(pkt, counter, 0, len, dma_mapped,
+					    page, pbc, dma_addr);
+
+		if (nfrags) {
+			ret = ipath_user_sdma_init_payload(dd, pq, pkt,
+							   iov + idx_save + 1,
+							   nfrags, npages);
+			if (ret < 0)
+				goto free_pbc_dma;
+		}
+
+		counter++;
+		npkts++;
+
+		list_add_tail(&pkt->list, list);
+	}
+
+	ret = idx;
+	goto done;
+
+free_pbc_dma:
+	if (dma_mapped)
+		dma_unmap_page(&dd->pcidev->dev, dma_addr, len, DMA_TO_DEVICE);
+free_pbc:
+	if (page) {
+		kunmap(page);
+		__free_page(page);
+	} else
+		dma_pool_free(pq->header_cache, pbc, dma_addr);
+free_pkt:
+	kmem_cache_free(pq->pkt_slab, pkt);
+free_list:
+	ipath_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, list);
+done:
+	return ret;
+}
+
+static void ipath_user_sdma_set_complete_counter(struct ipath_user_sdma_queue *pq,
+						 u32 c)
+{
+	pq->sent_counter = c;
+}
+
+/* try to clean out queue -- needs pq->lock */
+static int ipath_user_sdma_queue_clean(const struct ipath_devdata *dd,
+				       struct ipath_user_sdma_queue *pq)
+{
+	struct list_head free_list;
+	struct ipath_user_sdma_pkt *pkt;
+	struct ipath_user_sdma_pkt *pkt_prev;
+	int ret = 0;
+
+	INIT_LIST_HEAD(&free_list);
+
+	list_for_each_entry_safe(pkt, pkt_prev, &pq->sent, list) {
+		s64 descd = dd->ipath_sdma_descq_removed - pkt->added;
+
+		if (descd < 0)
+			break;
+
+		list_move_tail(&pkt->list, &free_list);
+
+		/* one more packet cleaned */
+		ret++;
+	}
+
+	if (!list_empty(&free_list)) {
+		u32 counter;
+
+		pkt = list_entry(free_list.prev,
+				 struct ipath_user_sdma_pkt, list);
+		counter = pkt->counter;
+
+		ipath_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &free_list);
+		ipath_user_sdma_set_complete_counter(pq, counter);
+	}
+
+	return ret;
+}
+
+void ipath_user_sdma_queue_destroy(struct ipath_user_sdma_queue *pq)
+{
+	if (!pq)
+		return;
+
+	kmem_cache_destroy(pq->pkt_slab);
+	dma_pool_destroy(pq->header_cache);
+	kfree(pq);
+}
+
+/* clean descriptor queue, returns > 0 if some elements cleaned */
+static int ipath_user_sdma_hwqueue_clean(struct ipath_devdata *dd)
+{
+	int ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dd->ipath_sdma_lock, flags);
+	ret = ipath_sdma_make_progress(dd);
+	spin_unlock_irqrestore(&dd->ipath_sdma_lock, flags);
+
+	return ret;
+}
+
+/* we're in close, drain packets so that we can cleanup successfully... */
+void ipath_user_sdma_queue_drain(struct ipath_devdata *dd,
+				 struct ipath_user_sdma_queue *pq)
+{
+	int i;
+
+	if (!pq)
+		return;
+
+	for (i = 0; i < 100; i++) {
+		mutex_lock(&pq->lock);
+		if (list_empty(&pq->sent)) {
+			mutex_unlock(&pq->lock);
+			break;
+		}
+		ipath_user_sdma_hwqueue_clean(dd);
+		ipath_user_sdma_queue_clean(dd, pq);
+		mutex_unlock(&pq->lock);
+		msleep(10);
+	}
+
+	if (!list_empty(&pq->sent)) {
+		struct list_head free_list;
+
+		printk(KERN_INFO "drain: lists not empty: forcing!\n");
+		INIT_LIST_HEAD(&free_list);
+		mutex_lock(&pq->lock);
+		list_splice_init(&pq->sent, &free_list);
+		ipath_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &free_list);
+		mutex_unlock(&pq->lock);
+	}
+}
+
+static inline __le64 ipath_sdma_make_desc0(struct ipath_devdata *dd,
+					   u64 addr, u64 dwlen, u64 dwoffset)
+{
+	return cpu_to_le64(/* SDmaPhyAddr[31:0] */
+			   ((addr & 0xfffffffcULL) << 32) |
+			   /* SDmaGeneration[1:0] */
+			   ((dd->ipath_sdma_generation & 3ULL) << 30) |
+			   /* SDmaDwordCount[10:0] */
+			   ((dwlen & 0x7ffULL) << 16) |
+			   /* SDmaBufOffset[12:2] */
+			   (dwoffset & 0x7ffULL));
+}
+
+static inline __le64 ipath_sdma_make_first_desc0(__le64 descq)
+{
+	return descq | __constant_cpu_to_le64(1ULL << 12);
+}
+
+static inline __le64 ipath_sdma_make_last_desc0(__le64 descq)
+{
+					      /* last */  /* dma head */
+	return descq | __constant_cpu_to_le64(1ULL << 11 | 1ULL << 13);
+}
+
+static inline __le64 ipath_sdma_make_desc1(u64 addr)
+{
+	/* SDmaPhyAddr[47:32] */
+	return cpu_to_le64(addr >> 32);
+}
+
+static void ipath_user_sdma_send_frag(struct ipath_devdata *dd,
+				      struct ipath_user_sdma_pkt *pkt, int idx,
+				      unsigned ofs, u16 tail)
+{
+	const u64 addr = (u64) pkt->addr[idx].addr +
+		(u64) pkt->addr[idx].offset;
+	const u64 dwlen = (u64) pkt->addr[idx].length / 4;
+	__le64 *descqp;
+	__le64 descq0;
+
+	descqp = &dd->ipath_sdma_descq[tail].qw[0];
+
+	descq0 = ipath_sdma_make_desc0(dd, addr, dwlen, ofs);
+	if (idx == 0)
+		descq0 = ipath_sdma_make_first_desc0(descq0);
+	if (idx == pkt->naddr - 1)
+		descq0 = ipath_sdma_make_last_desc0(descq0);
+
+	descqp[0] = descq0;
+	descqp[1] = ipath_sdma_make_desc1(addr);
+}
+
+/* pq->lock must be held, get packets on the wire... */
+static int ipath_user_sdma_push_pkts(struct ipath_devdata *dd,
+				     struct ipath_user_sdma_queue *pq,
+				     struct list_head *pktlist)
+{
+	int ret = 0;
+	unsigned long flags;
+	u16 tail;
+
+	if (list_empty(pktlist))
+		return 0;
+
+	if (unlikely(!(dd->ipath_flags & IPATH_LINKACTIVE)))
+		return -ECOMM;
+
+	spin_lock_irqsave(&dd->ipath_sdma_lock, flags);
+
+	if (unlikely(dd->ipath_sdma_status & IPATH_SDMA_ABORT_MASK)) {
+		ret = -ECOMM;
+		goto unlock;
+	}
+
+	tail = dd->ipath_sdma_descq_tail;
+	while (!list_empty(pktlist)) {
+		struct ipath_user_sdma_pkt *pkt =
+			list_entry(pktlist->next, struct ipath_user_sdma_pkt,
+				   list);
+		int i;
+		unsigned ofs = 0;
+		u16 dtail = tail;
+
+		if (pkt->naddr > ipath_sdma_descq_freecnt(dd))
+			goto unlock_check_tail;
+
+		for (i = 0; i < pkt->naddr; i++) {
+			ipath_user_sdma_send_frag(dd, pkt, i, ofs, tail);
+			ofs += pkt->addr[i].length >> 2;
+
+			if (++tail == dd->ipath_sdma_descq_cnt) {
+				tail = 0;
+				++dd->ipath_sdma_generation;
+			}
+		}
+
+		if ((ofs<<2) > dd->ipath_ibmaxlen) {
+			ipath_dbg("packet size %X > ibmax %X, fail\n",
+				ofs<<2, dd->ipath_ibmaxlen);
+			ret = -EMSGSIZE;
+			goto unlock;
+		}
+
+		/*
+		 * if the packet is >= 2KB mtu equivalent, we have to use
+		 * the large buffers, and have to mark each descriptor as
+		 * part of a large buffer packet.
+		 */
+		if (ofs >= IPATH_SMALLBUF_DWORDS) {
+			for (i = 0; i < pkt->naddr; i++) {
+				dd->ipath_sdma_descq[dtail].qw[0] |=
+					__constant_cpu_to_le64(1ULL << 14);
+				if (++dtail == dd->ipath_sdma_descq_cnt)
+					dtail = 0;
+			}
+		}
+
+		dd->ipath_sdma_descq_added += pkt->naddr;
+		pkt->added = dd->ipath_sdma_descq_added;
+		list_move_tail(&pkt->list, &pq->sent);
+		ret++;
+	}
+
+unlock_check_tail:
+	/* advance the tail on the chip if necessary */
+	if (dd->ipath_sdma_descq_tail != tail) {
+		wmb();
+		ipath_write_kreg(dd, dd->ipath_kregs->kr_senddmatail, tail);
+		dd->ipath_sdma_descq_tail = tail;
+	}
+
+unlock:
+	spin_unlock_irqrestore(&dd->ipath_sdma_lock, flags);
+
+	return ret;
+}
+
+int ipath_user_sdma_writev(struct ipath_devdata *dd,
+			   struct ipath_user_sdma_queue *pq,
+			   const struct iovec *iov,
+			   unsigned long dim)
+{
+	int ret = 0;
+	struct list_head list;
+	int npkts = 0;
+
+	INIT_LIST_HEAD(&list);
+
+	mutex_lock(&pq->lock);
+
+	if (dd->ipath_sdma_descq_added != dd->ipath_sdma_descq_removed) {
+		ipath_user_sdma_hwqueue_clean(dd);
+		ipath_user_sdma_queue_clean(dd, pq);
+	}
+
+	while (dim) {
+		const int mxp = 8;
+
+		down_write(&current->mm->mmap_sem);
+		ret = ipath_user_sdma_queue_pkts(dd, pq, &list, iov, dim, mxp);
+		up_write(&current->mm->mmap_sem);
+
+		if (ret <= 0)
+			goto done_unlock;
+		else {
+			dim -= ret;
+			iov += ret;
+		}
+
+		/* force packets onto the sdma hw queue... */
+		if (!list_empty(&list)) {
+			/*
+			 * lazily clean hw queue.  the 4 is a guess of about
+			 * how many sdma descriptors a packet will take (it
+			 * doesn't have to be perfect).
+			 */
+			if (ipath_sdma_descq_freecnt(dd) < ret * 4) {
+				ipath_user_sdma_hwqueue_clean(dd);
+				ipath_user_sdma_queue_clean(dd, pq);
+			}
+
+			ret = ipath_user_sdma_push_pkts(dd, pq, &list);
+			if (ret < 0)
+				goto done_unlock;
+			else {
+				npkts += ret;
+				pq->counter += ret;
+
+				if (!list_empty(&list))
+					goto done_unlock;
+			}
+		}
+	}
+
+done_unlock:
+	if (!list_empty(&list))
+		ipath_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &list);
+	mutex_unlock(&pq->lock);
+
+	return (ret < 0) ? ret : npkts;
+}
+
+int ipath_user_sdma_make_progress(struct ipath_devdata *dd,
+				  struct ipath_user_sdma_queue *pq)
+{
+	int ret = 0;
+
+	mutex_lock(&pq->lock);
+	ipath_user_sdma_hwqueue_clean(dd);
+	ret = ipath_user_sdma_queue_clean(dd, pq);
+	mutex_unlock(&pq->lock);
+
+	return ret;
+}
+
+u32 ipath_user_sdma_complete_counter(const struct ipath_user_sdma_queue *pq)
+{
+	return pq->sent_counter;
+}
+
+u32 ipath_user_sdma_inflight_counter(struct ipath_user_sdma_queue *pq)
+{
+	return pq->counter;
+}
+