drivers/infiniband/hw/qib/qib_user_sdma.c - kernel/mindspeed - Git at Google

 /*
  * Copyright (c) 2007, 2008, 2009 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 "qib.h"
 #include "qib_user_sdma.h"

 /* minimum size of header */
 #define QIB_USER_SDMA_MIN_HEADER_LENGTH 64
 /* expected size of headers (for dma_pool) */
 #define QIB_USER_SDMA_EXP_HEADER_LENGTH 64
 /* attempt to drain the queue for 5secs */
 #define QIB_USER_SDMA_DRAIN_TIMEOUT 500

 struct qib_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 qib_user_sdma_queue {
 	/*
 	 * pkts sent to dma engine are queued on this
 	 * list head.  the type of the elements of this
 	 * list are struct qib_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 qib_user_sdma_queue *
 qib_user_sdma_queue_create(struct device *dev, int unit, int ctxt, int sctxt)
 {
 	struct qib_user_sdma_queue *pq =
 		kmalloc(sizeof(struct qib_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),
 		 "qib-user-sdma-pkts-%u-%02u.%02u", unit, ctxt, sctxt);
 	pq->pkt_slab = kmem_cache_create(pq->pkt_slab_name,
 					 sizeof(struct qib_user_sdma_pkt),
 					 0, 0, NULL);

 	if (!pq->pkt_slab)
 		goto err_kfree;

 	snprintf(pq->header_cache_name, sizeof(pq->header_cache_name),
 		 "qib-user-sdma-headers-%u-%02u.%02u", unit, ctxt, sctxt);
 	pq->header_cache = dma_pool_create(pq->header_cache_name,
 					   dev,
 					   QIB_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 qib_user_sdma_init_frag(struct qib_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 qib_user_sdma_init_header(struct qib_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;
 	qib_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 qib_user_sdma_coalesce(const struct qib_devdata *dd,
 				  struct qib_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(&dd->pcidev->dev, dma_addr)) {
 		ret = -ENOMEM;
 		goto free_unmap;
 	}

 	qib_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 qib_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 boundary.
  */
 static int qib_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 qib_user_sdma_free_pkt_frag(struct device *dev,
 					struct qib_user_sdma_queue *pq,
 					struct qib_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 qib_user_sdma_pin_pages(const struct qib_devdata *dd,
 				   struct qib_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 = qib_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(&dd->pcidev->dev, dma_addr)) {
 			ret = -ENOMEM;
 			goto done;
 		}

 		qib_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 qib_user_sdma_pin_pkt(const struct qib_devdata *dd,
 				 struct qib_user_sdma_queue *pq,
 				 struct qib_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 = qib_user_sdma_num_pages(iov + idx);
 		const unsigned long addr = (unsigned long) iov[idx].iov_base;

 		ret = qib_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++)
 		qib_user_sdma_free_pkt_frag(&dd->pcidev->dev, pq, pkt, idx);

 done:
 	return ret;
 }

 static int qib_user_sdma_init_payload(const struct qib_devdata *dd,
 				      struct qib_user_sdma_queue *pq,
 				      struct qib_user_sdma_pkt *pkt,
 				      const struct iovec *iov,
 				      unsigned long niov, int npages)
 {
 	int ret = 0;

 	if (npages >= ARRAY_SIZE(pkt->addr))
 		ret = qib_user_sdma_coalesce(dd, pkt, iov, niov);
 	else
 		ret = qib_user_sdma_pin_pkt(dd, pq, pkt, iov, niov);

 	return ret;
 }

 /* free a packet list -- return counter value of last packet */
 static void qib_user_sdma_free_pkt_list(struct device *dev,
 					struct qib_user_sdma_queue *pq,
 					struct list_head *list)
 {
 	struct qib_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++)
 			qib_user_sdma_free_pkt_frag(dev, pq, pkt, i);

 		kmem_cache_free(pq->pkt_slab, pkt);
 	}
 	INIT_LIST_HEAD(list);
 }

 /*
  * 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 qib_user_sdma_queue_pkts(const struct qib_devdata *dd,
 				    struct qib_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 qib_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 < QIB_USER_SDMA_MIN_HEADER_LENGTH ||
 		    len > PAGE_SIZE || len & 3 || addr & 3) {
 			ret = -EINVAL;
 			goto free_pkt;
 		}

 		if (len == QIB_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) & QIB_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(&dd->pcidev->dev, dma_addr)) {
 				ret = -ENOMEM;
 				goto free_pbc;
 			}

 			dma_mapped = 1;
 		}

 		qib_user_sdma_init_header(pkt, counter, 0, len, dma_mapped,
 					  page, pbc, dma_addr);

 		if (nfrags) {
 			ret = qib_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:
 	qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, list);
 done:
 	return ret;
 }

 static void qib_user_sdma_set_complete_counter(struct qib_user_sdma_queue *pq,
 					       u32 c)
 {
 	pq->sent_counter = c;
 }

 /* try to clean out queue -- needs pq->lock */
 static int qib_user_sdma_queue_clean(struct qib_pportdata *ppd,
 				     struct qib_user_sdma_queue *pq)
 {
 	struct qib_devdata *dd = ppd->dd;
 	struct list_head free_list;
 	struct qib_user_sdma_pkt *pkt;
 	struct qib_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 = ppd->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 qib_user_sdma_pkt, list);
 		counter = pkt->counter;

 		qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &free_list);
 		qib_user_sdma_set_complete_counter(pq, counter);
 	}

 	return ret;
 }

 void qib_user_sdma_queue_destroy(struct qib_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 qib_user_sdma_hwqueue_clean(struct qib_pportdata *ppd)
 {
 	int ret;
 	unsigned long flags;

 	spin_lock_irqsave(&ppd->sdma_lock, flags);
 	ret = qib_sdma_make_progress(ppd);
 	spin_unlock_irqrestore(&ppd->sdma_lock, flags);

 	return ret;
 }

 /* we're in close, drain packets so that we can cleanup successfully... */
 void qib_user_sdma_queue_drain(struct qib_pportdata *ppd,
 			       struct qib_user_sdma_queue *pq)
 {
 	struct qib_devdata *dd = ppd->dd;
 	int i;

 	if (!pq)
 		return;

 	for (i = 0; i < QIB_USER_SDMA_DRAIN_TIMEOUT; i++) {
 		mutex_lock(&pq->lock);
 		if (list_empty(&pq->sent)) {
 			mutex_unlock(&pq->lock);
 			break;
 		}
 		qib_user_sdma_hwqueue_clean(ppd);
 		qib_user_sdma_queue_clean(ppd, pq);
 		mutex_unlock(&pq->lock);
 		msleep(10);
 	}

 	if (!list_empty(&pq->sent)) {
 		struct list_head free_list;

 		qib_dev_err(dd, "user sdma lists not empty: forcing!\n");
 		INIT_LIST_HEAD(&free_list);
 		mutex_lock(&pq->lock);
 		list_splice_init(&pq->sent, &free_list);
 		qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &free_list);
 		mutex_unlock(&pq->lock);
 	}
 }

 static inline __le64 qib_sdma_make_desc0(struct qib_pportdata *ppd,
 					 u64 addr, u64 dwlen, u64 dwoffset)
 {
 	u8 tmpgen;

 	tmpgen = ppd->sdma_generation;

 	return cpu_to_le64(/* SDmaPhyAddr[31:0] */
 			   ((addr & 0xfffffffcULL) << 32) |
 			   /* SDmaGeneration[1:0] */
 			   ((tmpgen & 3ULL) << 30) |
 			   /* SDmaDwordCount[10:0] */
 			   ((dwlen & 0x7ffULL) << 16) |
 			   /* SDmaBufOffset[12:2] */
 			   (dwoffset & 0x7ffULL));
 }

 static inline __le64 qib_sdma_make_first_desc0(__le64 descq)
 {
 	return descq | cpu_to_le64(1ULL << 12);
 }

 static inline __le64 qib_sdma_make_last_desc0(__le64 descq)
 {
 					      /* last */  /* dma head */
 	return descq | cpu_to_le64(1ULL << 11 | 1ULL << 13);
 }

 static inline __le64 qib_sdma_make_desc1(u64 addr)
 {
 	/* SDmaPhyAddr[47:32] */
 	return cpu_to_le64(addr >> 32);
 }

 static void qib_user_sdma_send_frag(struct qib_pportdata *ppd,
 				    struct qib_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 = &ppd->sdma_descq[tail].qw[0];

 	descq0 = qib_sdma_make_desc0(ppd, addr, dwlen, ofs);
 	if (idx == 0)
 		descq0 = qib_sdma_make_first_desc0(descq0);
 	if (idx == pkt->naddr - 1)
 		descq0 = qib_sdma_make_last_desc0(descq0);

 	descqp[0] = descq0;
 	descqp[1] = qib_sdma_make_desc1(addr);
 }

 /* pq->lock must be held, get packets on the wire... */
 static int qib_user_sdma_push_pkts(struct qib_pportdata *ppd,
 				   struct qib_user_sdma_queue *pq,
 				   struct list_head *pktlist)
 {
 	struct qib_devdata *dd = ppd->dd;
 	int ret = 0;
 	unsigned long flags;
 	u16 tail;
 	u8 generation;
 	u64 descq_added;

 	if (list_empty(pktlist))
 		return 0;

 	if (unlikely(!(ppd->lflags & QIBL_LINKACTIVE)))
 		return -ECOMM;

 	spin_lock_irqsave(&ppd->sdma_lock, flags);

 	/* keep a copy for restoring purposes in case of problems */
 	generation = ppd->sdma_generation;
 	descq_added = ppd->sdma_descq_added;

 	if (unlikely(!__qib_sdma_running(ppd))) {
 		ret = -ECOMM;
 		goto unlock;
 	}

 	tail = ppd->sdma_descq_tail;
 	while (!list_empty(pktlist)) {
 		struct qib_user_sdma_pkt *pkt =
 			list_entry(pktlist->next, struct qib_user_sdma_pkt,
 				   list);
 		int i;
 		unsigned ofs = 0;
 		u16 dtail = tail;

 		if (pkt->naddr > qib_sdma_descq_freecnt(ppd))
 			goto unlock_check_tail;

 		for (i = 0; i < pkt->naddr; i++) {
 			qib_user_sdma_send_frag(ppd, pkt, i, ofs, tail);
 			ofs += pkt->addr[i].length >> 2;

 			if (++tail == ppd->sdma_descq_cnt) {
 				tail = 0;
 				++ppd->sdma_generation;
 			}
 		}

 		if ((ofs << 2) > ppd->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 > dd->piosize2kmax_dwords) {
 			for (i = 0; i < pkt->naddr; i++) {
 				ppd->sdma_descq[dtail].qw[0] |=
 					cpu_to_le64(1ULL << 14);
 				if (++dtail == ppd->sdma_descq_cnt)
 					dtail = 0;
 			}
 		}

 		ppd->sdma_descq_added += pkt->naddr;
 		pkt->added = ppd->sdma_descq_added;
 		list_move_tail(&pkt->list, &pq->sent);
 		ret++;
 	}

 unlock_check_tail:
 	/* advance the tail on the chip if necessary */
 	if (ppd->sdma_descq_tail != tail)
 		dd->f_sdma_update_tail(ppd, tail);

 unlock:
 	if (unlikely(ret < 0)) {
 		ppd->sdma_generation = generation;
 		ppd->sdma_descq_added = descq_added;
 	}
 	spin_unlock_irqrestore(&ppd->sdma_lock, flags);

 	return ret;
 }

 int qib_user_sdma_writev(struct qib_ctxtdata *rcd,
 			 struct qib_user_sdma_queue *pq,
 			 const struct iovec *iov,
 			 unsigned long dim)
 {
 	struct qib_devdata *dd = rcd->dd;
 	struct qib_pportdata *ppd = rcd->ppd;
 	int ret = 0;
 	struct list_head list;
 	int npkts = 0;

 	INIT_LIST_HEAD(&list);

 	mutex_lock(&pq->lock);

 	/* why not -ECOMM like qib_user_sdma_push_pkts() below? */
 	if (!qib_sdma_running(ppd))
 		goto done_unlock;

 	if (ppd->sdma_descq_added != ppd->sdma_descq_removed) {
 		qib_user_sdma_hwqueue_clean(ppd);
 		qib_user_sdma_queue_clean(ppd, pq);
 	}

 	while (dim) {
 		const int mxp = 8;

 		down_write(&current->mm->mmap_sem);
 		ret = qib_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 (qib_sdma_descq_freecnt(ppd) < ret * 4) {
 				qib_user_sdma_hwqueue_clean(ppd);
 				qib_user_sdma_queue_clean(ppd, pq);
 			}

 			ret = qib_user_sdma_push_pkts(ppd, 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))
 		qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &list);
 	mutex_unlock(&pq->lock);

 	return (ret < 0) ? ret : npkts;
 }

 int qib_user_sdma_make_progress(struct qib_pportdata *ppd,
 				struct qib_user_sdma_queue *pq)
 {
 	int ret = 0;

 	mutex_lock(&pq->lock);
 	qib_user_sdma_hwqueue_clean(ppd);
 	ret = qib_user_sdma_queue_clean(ppd, pq);
 	mutex_unlock(&pq->lock);

 	return ret;
 }

 u32 qib_user_sdma_complete_counter(const struct qib_user_sdma_queue *pq)
 {
 	return pq ? pq->sent_counter : 0;
 }

 u32 qib_user_sdma_inflight_counter(struct qib_user_sdma_queue *pq)
 {
 	return pq ? pq->counter : 0;
 }
	/*
	* Copyright (c) 2007, 2008, 2009 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 "qib.h"
	#include "qib_user_sdma.h"

	/* minimum size of header */
	#define QIB_USER_SDMA_MIN_HEADER_LENGTH 64
	/* expected size of headers (for dma_pool) */
	#define QIB_USER_SDMA_EXP_HEADER_LENGTH 64
	/* attempt to drain the queue for 5secs */
	#define QIB_USER_SDMA_DRAIN_TIMEOUT 500

	struct qib_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 qib_user_sdma_queue {
	/*
	* pkts sent to dma engine are queued on this
	* list head. the type of the elements of this
	* list are struct qib_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 qib_user_sdma_queue *
	qib_user_sdma_queue_create(struct device *dev, int unit, int ctxt, int sctxt)
	{
	struct qib_user_sdma_queue *pq =
	kmalloc(sizeof(struct qib_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),
	"qib-user-sdma-pkts-%u-%02u.%02u", unit, ctxt, sctxt);
	pq->pkt_slab = kmem_cache_create(pq->pkt_slab_name,
	sizeof(struct qib_user_sdma_pkt),
	0, 0, NULL);

	if (!pq->pkt_slab)
	goto err_kfree;

	snprintf(pq->header_cache_name, sizeof(pq->header_cache_name),
	"qib-user-sdma-headers-%u-%02u.%02u", unit, ctxt, sctxt);
	pq->header_cache = dma_pool_create(pq->header_cache_name,
	dev,
	QIB_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 qib_user_sdma_init_frag(struct qib_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 qib_user_sdma_init_header(struct qib_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;
	qib_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 qib_user_sdma_coalesce(const struct qib_devdata *dd,
	struct qib_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(&dd->pcidev->dev, dma_addr)) {
	ret = -ENOMEM;
	goto free_unmap;
	}

	qib_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 qib_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 boundary.
	*/
	static int qib_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 qib_user_sdma_free_pkt_frag(struct device *dev,
	struct qib_user_sdma_queue *pq,
	struct qib_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 qib_user_sdma_pin_pages(const struct qib_devdata *dd,
	struct qib_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 = qib_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(&dd->pcidev->dev, dma_addr)) {
	ret = -ENOMEM;
	goto done;
	}

	qib_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 qib_user_sdma_pin_pkt(const struct qib_devdata *dd,
	struct qib_user_sdma_queue *pq,
	struct qib_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 = qib_user_sdma_num_pages(iov + idx);
	const unsigned long addr = (unsigned long) iov[idx].iov_base;

	ret = qib_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++)
	qib_user_sdma_free_pkt_frag(&dd->pcidev->dev, pq, pkt, idx);

	done:
	return ret;
	}

	static int qib_user_sdma_init_payload(const struct qib_devdata *dd,
	struct qib_user_sdma_queue *pq,
	struct qib_user_sdma_pkt *pkt,
	const struct iovec *iov,
	unsigned long niov, int npages)
	{
	int ret = 0;

	if (npages >= ARRAY_SIZE(pkt->addr))
	ret = qib_user_sdma_coalesce(dd, pkt, iov, niov);
	else
	ret = qib_user_sdma_pin_pkt(dd, pq, pkt, iov, niov);

	return ret;
	}

	/* free a packet list -- return counter value of last packet */
	static void qib_user_sdma_free_pkt_list(struct device *dev,
	struct qib_user_sdma_queue *pq,
	struct list_head *list)
	{
	struct qib_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++)
	qib_user_sdma_free_pkt_frag(dev, pq, pkt, i);

	kmem_cache_free(pq->pkt_slab, pkt);
	}
	INIT_LIST_HEAD(list);
	}

	/*
	* 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 qib_user_sdma_queue_pkts(const struct qib_devdata *dd,
	struct qib_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 qib_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 < QIB_USER_SDMA_MIN_HEADER_LENGTH \|\|
	len > PAGE_SIZE \|\| len & 3 \|\| addr & 3) {
	ret = -EINVAL;
	goto free_pkt;
	}

	if (len == QIB_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) & QIB_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(&dd->pcidev->dev, dma_addr)) {
	ret = -ENOMEM;
	goto free_pbc;
	}

	dma_mapped = 1;
	}

	qib_user_sdma_init_header(pkt, counter, 0, len, dma_mapped,
	page, pbc, dma_addr);

	if (nfrags) {
	ret = qib_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:
	qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, list);
	done:
	return ret;
	}

	static void qib_user_sdma_set_complete_counter(struct qib_user_sdma_queue *pq,
	u32 c)
	{
	pq->sent_counter = c;
	}

	/* try to clean out queue -- needs pq->lock */
	static int qib_user_sdma_queue_clean(struct qib_pportdata *ppd,
	struct qib_user_sdma_queue *pq)
	{
	struct qib_devdata *dd = ppd->dd;
	struct list_head free_list;
	struct qib_user_sdma_pkt *pkt;
	struct qib_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 = ppd->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 qib_user_sdma_pkt, list);
	counter = pkt->counter;

	qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &free_list);
	qib_user_sdma_set_complete_counter(pq, counter);
	}

	return ret;
	}

	void qib_user_sdma_queue_destroy(struct qib_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 qib_user_sdma_hwqueue_clean(struct qib_pportdata *ppd)
	{
	int ret;
	unsigned long flags;

	spin_lock_irqsave(&ppd->sdma_lock, flags);
	ret = qib_sdma_make_progress(ppd);
	spin_unlock_irqrestore(&ppd->sdma_lock, flags);

	return ret;
	}

	/* we're in close, drain packets so that we can cleanup successfully... */
	void qib_user_sdma_queue_drain(struct qib_pportdata *ppd,
	struct qib_user_sdma_queue *pq)
	{
	struct qib_devdata *dd = ppd->dd;
	int i;

	if (!pq)
	return;

	for (i = 0; i < QIB_USER_SDMA_DRAIN_TIMEOUT; i++) {
	mutex_lock(&pq->lock);
	if (list_empty(&pq->sent)) {
	mutex_unlock(&pq->lock);
	break;
	}
	qib_user_sdma_hwqueue_clean(ppd);
	qib_user_sdma_queue_clean(ppd, pq);
	mutex_unlock(&pq->lock);
	msleep(10);
	}

	if (!list_empty(&pq->sent)) {
	struct list_head free_list;

	qib_dev_err(dd, "user sdma lists not empty: forcing!\n");
	INIT_LIST_HEAD(&free_list);
	mutex_lock(&pq->lock);
	list_splice_init(&pq->sent, &free_list);
	qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &free_list);
	mutex_unlock(&pq->lock);
	}
	}

	static inline __le64 qib_sdma_make_desc0(struct qib_pportdata *ppd,
	u64 addr, u64 dwlen, u64 dwoffset)
	{
	u8 tmpgen;

	tmpgen = ppd->sdma_generation;

	return cpu_to_le64(/* SDmaPhyAddr[31:0] */
	((addr & 0xfffffffcULL) << 32) \|
	/* SDmaGeneration[1:0] */
	((tmpgen & 3ULL) << 30) \|
	/* SDmaDwordCount[10:0] */
	((dwlen & 0x7ffULL) << 16) \|
	/* SDmaBufOffset[12:2] */
	(dwoffset & 0x7ffULL));
	}

	static inline __le64 qib_sdma_make_first_desc0(__le64 descq)
	{
	return descq \| cpu_to_le64(1ULL << 12);
	}

	static inline __le64 qib_sdma_make_last_desc0(__le64 descq)
	{
	/* last / / dma head */
	return descq \| cpu_to_le64(1ULL << 11 \| 1ULL << 13);
	}

	static inline __le64 qib_sdma_make_desc1(u64 addr)
	{
	/* SDmaPhyAddr[47:32] */
	return cpu_to_le64(addr >> 32);
	}

	static void qib_user_sdma_send_frag(struct qib_pportdata *ppd,
	struct qib_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 = &ppd->sdma_descq[tail].qw[0];

	descq0 = qib_sdma_make_desc0(ppd, addr, dwlen, ofs);
	if (idx == 0)
	descq0 = qib_sdma_make_first_desc0(descq0);
	if (idx == pkt->naddr - 1)
	descq0 = qib_sdma_make_last_desc0(descq0);

	descqp[0] = descq0;
	descqp[1] = qib_sdma_make_desc1(addr);
	}

	/* pq->lock must be held, get packets on the wire... */
	static int qib_user_sdma_push_pkts(struct qib_pportdata *ppd,
	struct qib_user_sdma_queue *pq,
	struct list_head *pktlist)
	{
	struct qib_devdata *dd = ppd->dd;
	int ret = 0;
	unsigned long flags;
	u16 tail;
	u8 generation;
	u64 descq_added;

	if (list_empty(pktlist))
	return 0;

	if (unlikely(!(ppd->lflags & QIBL_LINKACTIVE)))
	return -ECOMM;

	spin_lock_irqsave(&ppd->sdma_lock, flags);

	/* keep a copy for restoring purposes in case of problems */
	generation = ppd->sdma_generation;
	descq_added = ppd->sdma_descq_added;

	if (unlikely(!__qib_sdma_running(ppd))) {
	ret = -ECOMM;
	goto unlock;
	}

	tail = ppd->sdma_descq_tail;
	while (!list_empty(pktlist)) {
	struct qib_user_sdma_pkt *pkt =
	list_entry(pktlist->next, struct qib_user_sdma_pkt,
	list);
	int i;
	unsigned ofs = 0;
	u16 dtail = tail;

	if (pkt->naddr > qib_sdma_descq_freecnt(ppd))
	goto unlock_check_tail;

	for (i = 0; i < pkt->naddr; i++) {
	qib_user_sdma_send_frag(ppd, pkt, i, ofs, tail);
	ofs += pkt->addr[i].length >> 2;

	if (++tail == ppd->sdma_descq_cnt) {
	tail = 0;
	++ppd->sdma_generation;
	}
	}

	if ((ofs << 2) > ppd->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 > dd->piosize2kmax_dwords) {
	for (i = 0; i < pkt->naddr; i++) {
	ppd->sdma_descq[dtail].qw[0] \|=
	cpu_to_le64(1ULL << 14);
	if (++dtail == ppd->sdma_descq_cnt)
	dtail = 0;
	}
	}

	ppd->sdma_descq_added += pkt->naddr;
	pkt->added = ppd->sdma_descq_added;
	list_move_tail(&pkt->list, &pq->sent);
	ret++;
	}

	unlock_check_tail:
	/* advance the tail on the chip if necessary */
	if (ppd->sdma_descq_tail != tail)
	dd->f_sdma_update_tail(ppd, tail);

	unlock:
	if (unlikely(ret < 0)) {
	ppd->sdma_generation = generation;
	ppd->sdma_descq_added = descq_added;
	}
	spin_unlock_irqrestore(&ppd->sdma_lock, flags);

	return ret;
	}

	int qib_user_sdma_writev(struct qib_ctxtdata *rcd,
	struct qib_user_sdma_queue *pq,
	const struct iovec *iov,
	unsigned long dim)
	{
	struct qib_devdata *dd = rcd->dd;
	struct qib_pportdata *ppd = rcd->ppd;
	int ret = 0;
	struct list_head list;
	int npkts = 0;

	INIT_LIST_HEAD(&list);

	mutex_lock(&pq->lock);

	/* why not -ECOMM like qib_user_sdma_push_pkts() below? */
	if (!qib_sdma_running(ppd))
	goto done_unlock;

	if (ppd->sdma_descq_added != ppd->sdma_descq_removed) {
	qib_user_sdma_hwqueue_clean(ppd);
	qib_user_sdma_queue_clean(ppd, pq);
	}

	while (dim) {
	const int mxp = 8;

	down_write(&current->mm->mmap_sem);
	ret = qib_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 (qib_sdma_descq_freecnt(ppd) < ret * 4) {
	qib_user_sdma_hwqueue_clean(ppd);
	qib_user_sdma_queue_clean(ppd, pq);
	}

	ret = qib_user_sdma_push_pkts(ppd, 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))
	qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &list);
	mutex_unlock(&pq->lock);

	return (ret < 0) ? ret : npkts;
	}

	int qib_user_sdma_make_progress(struct qib_pportdata *ppd,
	struct qib_user_sdma_queue *pq)
	{
	int ret = 0;

	mutex_lock(&pq->lock);
	qib_user_sdma_hwqueue_clean(ppd);
	ret = qib_user_sdma_queue_clean(ppd, pq);
	mutex_unlock(&pq->lock);

	return ret;
	}

	u32 qib_user_sdma_complete_counter(const struct qib_user_sdma_queue *pq)
	{
	return pq ? pq->sent_counter : 0;
	}

	u32 qib_user_sdma_inflight_counter(struct qib_user_sdma_queue *pq)
	{
	return pq ? pq->counter : 0;
	}