[v2,08/17] soc: qcom: ipa: GSI transactions

diff --git a/drivers/net/ipa/gsi_trans.c b/drivers/net/ipa/gsi_trans.c
new file mode 100644
index 000000000000..267e33093554
--- /dev/null
+++ b/drivers/net/ipa/gsi_trans.c
@@ -0,0 +1,624 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+/* Copyright (c) 2012-2018, The Linux Foundation. All rights reserved.
+ * Copyright (C) 2019 Linaro Ltd.
+ */
+
+#include <linux/types.h>
+#include <linux/bits.h>
+#include <linux/bitfield.h>
+#include <linux/refcount.h>
+#include <linux/scatterlist.h>
+
+#include "gsi.h"
+#include "gsi_private.h"
+#include "gsi_trans.h"
+#include "ipa_gsi.h"
+#include "ipa_data.h"
+#include "ipa_cmd.h"
+
+/**
+ * DOC: GSI Transactions
+ *
+ * A GSI transaction abstracts the behavior of a GSI channel by representing
+ * everything about a related group of data transfers in a single structure.
+ * Most details of interaction with the GSI hardware are managed by the GSI
+ * transaction core, allowing users to simply describe transfers to be
+ * performed.  When a transaction has completed a callback function
+ * (dependent on the type of endpoint associated with the channel) allows
+ * cleanup of resources associated with the transaction.
+ *
+ * To perform a data transfer (or a related set of them), a user of the GSI
+ * transaction interface allocates a transaction, indicating the number of
+ * TREs required (one per data transfer).  If sufficient TREs are available,
+ * they are reserved for use in the transaction and the allocation succeeds.
+ * This way exhaustion of the available TREs in a channel ring is detected
+ * as early as possible.  All resources required to complete a transaction
+ * are allocated at transaction allocation time.
+ *
+ * Transfers performed as part of a transaction are represented in an array
+ * of Linux scatterlist structures.  This array is allocated with the
+ * transaction, and its entries must be initialized using standard
+ * scatterlist functions (such as sg_init_one() or skb_to_sgvec()).
+ *
+ * Once a transaction's scatterlist structures have been initialized, the
+ * transaction is committed.  The GSI transaction layer is responsible for
+ * DMA mapping (and unmapping) memory described in the transaction's
+ * scatterlist array.  The only way committing a transaction fails is if
+ * this DMA mapping step returns an error.  Otherwise, ownership of the
+ * entire transaction is transferred to the GSI transaction core.  The GSI
+ * transaction code formats the content of the scatterlist array into the
+ * channel ring buffer and informs the hardware that new TREs are available
+ * to process.
+ *
+ * The last TRE in each transaction is marked to interrupt the AP when the
+ * GSI hardware has completed it.  Because transfers described by TREs are
+ * performed strictly in order, signaling the completion of just the last
+ * TRE in the transaction is sufficient to indicate the full transaction
+ * is complete.
+ *
+ * When a transaction is complete, ipa_gsi_trans_complete() is called by the
+ * GSI code into the IPA layer, allowing it to perform any final cleanup
+ * required before the transaction is freed.
+ */
+
+/* gsi_tre->flags mask values (in CPU byte order) */
+#define GSI_TRE_FLAGS_CHAIN_FMASK	GENMASK(0, 0)
+#define GSI_TRE_FLAGS_IEOB_FMASK	GENMASK(8, 8)
+#define GSI_TRE_FLAGS_IEOT_FMASK	GENMASK(9, 9)
+#define GSI_TRE_FLAGS_BEI_FMASK		GENMASK(10, 10)
+#define GSI_TRE_FLAGS_TYPE_FMASK	GENMASK(23, 16)
+
+/* Hardware values representing a transfer element type */
+enum gsi_tre_type {
+	GSI_RE_XFER	= 0x2,
+	GSI_RE_IMMD_CMD	= 0x3,
+	GSI_RE_NOP	= 0x4,
+};
+
+/* Map a given ring entry index to the transaction associated with it */
+static void gsi_channel_trans_map(struct gsi_channel *channel, u32 index,
+				  struct gsi_trans *trans)
+{
+	/* Note: index *must* be used modulo the ring count here */
+	channel->trans_info.map[index % channel->tre_ring.count] = trans;
+}
+
+/* Return the transaction mapped to a given ring entry */
+struct gsi_trans *
+gsi_channel_trans_mapped(struct gsi_channel *channel, u32 index)
+{
+	/* Note: index *must* be used modulo the ring count here */
+	return channel->trans_info.map[index % channel->tre_ring.count];
+}
+
+/* Return the oldest completed transaction for a channel (or null) */
+struct gsi_trans *gsi_channel_trans_complete(struct gsi_channel *channel)
+{
+	return list_first_entry_or_null(&channel->trans_info.complete,
+					struct gsi_trans, links);
+}
+
+/* Move a transaction from the allocated list to the pending list */
+static void gsi_trans_move_pending(struct gsi_trans *trans)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+
+	spin_lock_bh(&trans_info->spinlock);
+
+	list_move_tail(&trans->links, &trans_info->pending);
+
+	spin_unlock_bh(&trans_info->spinlock);
+}
+
+/* Move a transaction and all of its predecessors from the pending list
+ * to the completed list.
+ */
+void gsi_trans_move_complete(struct gsi_trans *trans)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+	struct list_head list;
+
+	spin_lock_bh(&trans_info->spinlock);
+
+	/* Move this transaction and all predecessors to completed list */
+	list_cut_position(&list, &trans_info->pending, &trans->links);
+	list_splice_tail(&list, &trans_info->complete);
+
+	spin_unlock_bh(&trans_info->spinlock);
+}
+
+/* Move a transaction from the completed list to the polled list */
+void gsi_trans_move_polled(struct gsi_trans *trans)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+
+	spin_lock_bh(&trans_info->spinlock);
+
+	list_move_tail(&trans->links, &trans_info->polled);
+
+	spin_unlock_bh(&trans_info->spinlock);
+}
+
+/* Return the last (most recent) transaction allocated on a channel */
+struct gsi_trans *gsi_channel_trans_last(struct gsi *gsi, u32 channel_id)
+{
+	struct gsi_trans_info *trans_info;
+	struct gsi_trans *trans;
+	struct list_head *list;
+
+	trans_info = &gsi->channel[channel_id].trans_info;
+
+	spin_lock_bh(&trans_info->spinlock);
+
+	/* Find the last list to which a transaction was added */
+	if (!list_empty(&trans_info->alloc))
+		list = &trans_info->alloc;
+	else if (!list_empty(&trans_info->pending))
+		list = &trans_info->pending;
+	else if (!list_empty(&trans_info->complete))
+		list = &trans_info->complete;
+	else if (!list_empty(&trans_info->polled))
+		list = &trans_info->polled;
+	else
+		list = NULL;
+
+	if (list) {
+		/* The last entry on this list is the last one allocated.
+		 * Grab a reference so it can be waited for.
+		 */
+		trans = list_last_entry(list, struct gsi_trans, links);
+		refcount_inc(&trans->refcount);
+	} else {
+		trans = NULL;
+	}
+
+	spin_unlock_bh(&trans_info->spinlock);
+
+	return trans;
+}
+
+/* Reserve some number of TREs on a channel.  Returns true if successful */
+static bool
+gsi_trans_tre_reserve(struct gsi_trans_info *trans_info, u32 tre_count)
+{
+	int avail = atomic_read(&trans_info->tre_avail);
+	int new;
+
+	do {
+		new = avail - (int)tre_count;
+		if (unlikely(new < 0))
+			return false;
+	} while (!atomic_try_cmpxchg(&trans_info->tre_avail, &avail, new));
+
+	return true;
+}
+
+/* Release previously-reserved TRE entries to a channel */
+static void
+gsi_trans_tre_release(struct gsi_trans_info *trans_info, u32 tre_count)
+{
+	atomic_add(tre_count, &trans_info->tre_avail);
+}
+
+/* Allocate a GSI transaction on a channel */
+struct gsi_trans *
+gsi_channel_trans_alloc(struct gsi *gsi, u32 channel_id, u32 tre_count)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+	struct gsi_trans_info *trans_info;
+	struct gsi_trans *trans;
+	u32 which;
+
+	/* Caller should know the limit is gsi_channel_trans_max() */
+	if (WARN_ON(tre_count > channel->data->tlv_count))
+		return NULL;
+
+	trans_info = &channel->trans_info;
+
+	/* We reserve the TREs now, but consume them at commit time.
+	 * If there aren't enough available, we're done.
+	 */
+	if (!gsi_trans_tre_reserve(trans_info, tre_count))
+		return NULL;
+
+	/* Allocate the transaction and initialize it */
+	which = trans_info->pool_free++ % trans_info->pool_count;
+	trans = &trans_info->pool[which];
+
+	trans->gsi = gsi;
+	trans->channel_id = channel_id;
+	refcount_set(&trans->refcount, 1);
+	trans->tre_count = tre_count;
+	init_completion(&trans->completion);
+
+	/* We're reusing, so make sure all fields are reinitialized */
+	trans->dev = gsi->dev;
+	trans->result = 0;	/* Success assumed unless overwritten */
+	trans->data = NULL;
+
+	/* Allocate the scatter/gather entries it will use.  If what's
+	 * needed would cross the end-of-pool boundary, allocate them
+	 * from the beginning of the pool.
+	 */
+	if (tre_count > trans_info->sg_pool_count - trans_info->sg_pool_free)
+		trans_info->sg_pool_free = 0;
+	trans->sgl = &trans_info->sg_pool[trans_info->sg_pool_free];
+	trans->sgc = tre_count;
+	trans_info->sg_pool_free += tre_count;
+
+	spin_lock_bh(&trans_info->spinlock);
+
+	list_add_tail(&trans->links, &trans_info->alloc);
+
+	spin_unlock_bh(&trans_info->spinlock);
+
+	return trans;
+}
+
+/* Free a previously-allocated transaction (used only in case of error) */
+void gsi_trans_free(struct gsi_trans *trans)
+{
+	struct gsi_trans_info *trans_info;
+
+	if (!refcount_dec_and_test(&trans->refcount))
+		return;
+
+	trans_info = &trans->gsi->channel[trans->channel_id].trans_info;
+
+	spin_lock_bh(&trans_info->spinlock);
+
+	list_del(&trans->links);
+
+	spin_unlock_bh(&trans_info->spinlock);
+
+	gsi_trans_tre_release(trans_info, trans->tre_count);
+}
+
+/* Compute the length/opcode value to use for a TRE */
+static __le16 gsi_tre_len_opcode(enum ipa_cmd_opcode opcode, u32 len)
+{
+	return opcode == IPA_CMD_NONE ? cpu_to_le16((u16)len)
+				      : cpu_to_le16((u16)opcode);
+}
+
+/* Compute the flags value to use for a given TRE */
+static __le32 gsi_tre_flags(bool last_tre, bool bei, enum ipa_cmd_opcode opcode)
+{
+	enum gsi_tre_type tre_type;
+	u32 tre_flags;
+
+	tre_type = opcode == IPA_CMD_NONE ? GSI_RE_XFER : GSI_RE_IMMD_CMD;
+	tre_flags = u32_encode_bits(tre_type, GSI_TRE_FLAGS_TYPE_FMASK);
+
+	/* Last TRE contains interrupt flags */
+	if (last_tre) {
+		/* All transactions end in a transfer completion interrupt */
+		tre_flags |= GSI_TRE_FLAGS_IEOT_FMASK;
+		/* Don't interrupt when outbound commands are acknowledged */
+		if (bei)
+			tre_flags |= GSI_TRE_FLAGS_BEI_FMASK;
+	} else {	/* All others indicate there's more to come */
+		tre_flags |= GSI_TRE_FLAGS_CHAIN_FMASK;
+	}
+
+	return cpu_to_le32(tre_flags);
+}
+
+static void gsi_trans_tre_fill(struct gsi_tre *dest_tre, dma_addr_t addr,
+			       u32 len, bool last_tre, bool bei,
+			       enum ipa_cmd_opcode opcode)
+{
+	struct gsi_tre tre;
+
+	tre.addr = cpu_to_le64(addr);
+	tre.len_opcode = gsi_tre_len_opcode(opcode, len);
+	tre.reserved = 0;
+	tre.flags = gsi_tre_flags(last_tre, bei, opcode);
+
+	/* ARM64 can write 16 bytes as a unit with a single instruction.
+	 * Doing the assignment this way is an attempt to make that happen.
+	 */
+	*dest_tre = tre;
+}
+
+/* Issue a command to read a single byte from a channel */
+int gsi_trans_read_byte(struct gsi *gsi, u32 channel_id, dma_addr_t addr)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+	struct gsi_trans_info *trans_info;
+	struct gsi_ring *tre_ring;
+	struct gsi_tre *dest_tre;
+	struct gsi_ring *ring;
+
+	trans_info = &channel->trans_info;
+
+	/* First reserve the TRE, if possible */
+	if (!gsi_trans_tre_reserve(trans_info, 1))
+		return -EBUSY;
+
+	/* Now allocate the next TRE, fill it, and tell the hardware */
+	tre_ring = &channel->tre_ring;
+	ring = &gsi->evt_ring[channel->evt_ring_id].ring;
+
+	dest_tre = gsi_ring_virt(tre_ring, tre_ring->index);
+	gsi_trans_tre_fill(dest_tre, addr, 1, true, false, IPA_CMD_NONE);
+
+	tre_ring->index++;
+	gsi_channel_doorbell(channel);
+
+	return 0;
+}
+
+/* Mark a gsi_trans_read_byte() request done */
+void gsi_trans_read_byte_done(struct gsi *gsi, u32 channel_id)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+
+	gsi_trans_tre_release(&channel->trans_info, 1);
+}
+
+/**
+ * __gsi_trans_commit() - Common GSI transaction commit code
+ * @trans:	Transaction to commit
+ * @opcode:	Immediate command opcode, or IPA_CMD_NONE
+ * @ring_db:	Whether to tell the hardware about these queued transfers
+ *
+ * @Return:	0 if successful, or a negative error code
+ *
+ * Maps the transactions's scatterlist array for DMA, and returns -ENOMEM
+ * if that fails.  Formats channel ring TRE entries based on the content of
+ * the scatterlist.  Maps a transaction pointer to the last ring entry used
+ * for the transaction, so it can be recovered when it completes.  Moves
+ * the transaction to the pending list.  Finally, updates the channel ring
+ * pointer and optionally rings the doorbell.
+ */
+static int __gsi_trans_commit(struct gsi_trans *trans,
+			      enum ipa_cmd_opcode opcode, bool ring_db)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	struct gsi_ring *tre_ring = &channel->tre_ring;
+	enum dma_data_direction direction;
+	bool bei = channel->toward_ipa;
+	struct gsi_tre *dest_tre;
+	struct scatterlist *sg;
+	struct gsi_ring *ring;
+	u32 byte_count = 0;
+	u32 avail;
+	int ret;
+	u32 i;
+
+	direction = channel->toward_ipa ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+	ret = dma_map_sg(trans->dev, trans->sgl, trans->sgc, direction);
+	if (!ret)
+		return -ENOMEM;
+
+	ring = &channel->gsi->evt_ring[channel->evt_ring_id].ring;
+
+	/* Consume the entries.  If we cross the end of the ring while
+	 * filling them we'll switch to the beginning to finish.
+	 */
+	avail = ring->count - tre_ring->index % tre_ring->count;
+	dest_tre = gsi_ring_virt(tre_ring, tre_ring->index);
+	for_each_sg(trans->sgl, sg, trans->sgc, i) {
+		bool last_tre = i == trans->tre_count - 1;
+		dma_addr_t addr = sg_dma_address(sg);
+		u32 len = sg_dma_len(sg);
+
+		byte_count += len;
+		if (!avail--)
+			dest_tre = gsi_ring_virt(tre_ring, 0);
+
+		gsi_trans_tre_fill(dest_tre, addr, len, last_tre, bei, opcode);
+		dest_tre++;
+	}
+	tre_ring->index += trans->tre_count;
+
+	if (channel->toward_ipa) {
+		/* We record TX bytes when they are sent */
+		trans->len = byte_count;
+		trans->trans_count = channel->trans_count;
+		trans->byte_count = channel->byte_count;
+		channel->trans_count++;
+		channel->byte_count += byte_count;
+	}
+
+	/* Associate the last TRE with the transaction */
+	gsi_channel_trans_map(channel, tre_ring->index - 1, trans);
+
+	gsi_trans_move_pending(trans);
+
+	/* Ring doorbell if requested, or if all TREs are allocated */
+	if (ring_db || !atomic_read(&channel->trans_info.tre_avail)) {
+		/* Report what we're handing off to hardware for TX channels */
+		if (channel->toward_ipa)
+			gsi_channel_tx_queued(channel);
+		gsi_channel_doorbell(channel);
+	}
+
+	return 0;
+}
+
+/* Commit a GSI transaction */
+int gsi_trans_commit(struct gsi_trans *trans, bool ring_db)
+{
+	return __gsi_trans_commit(trans, IPA_CMD_NONE, ring_db);
+}
+
+/* Commit a GSI command transaction and wait for it to complete */
+int gsi_trans_commit_command(struct gsi_trans *trans,
+			     enum ipa_cmd_opcode opcode)
+{
+	int ret;
+
+	refcount_inc(&trans->refcount);
+
+	ret = __gsi_trans_commit(trans, opcode, true);
+	if (ret)
+		goto out_free_trans;
+
+	wait_for_completion(&trans->completion);
+
+out_free_trans:
+	gsi_trans_free(trans);
+
+	return ret;
+}
+
+/* Commit a GSI command transaction, wait for it to complete, with timeout */
+int gsi_trans_commit_command_timeout(struct gsi_trans *trans,
+				     enum ipa_cmd_opcode opcode,
+				     unsigned long timeout)
+{
+	unsigned long timeout_jiffies = msecs_to_jiffies(timeout);
+	unsigned long remaining;
+	int ret;
+
+	refcount_inc(&trans->refcount);
+
+	ret = __gsi_trans_commit(trans, opcode, true);
+	if (ret)
+		goto out_free_trans;
+
+	remaining = wait_for_completion_timeout(&trans->completion,
+						timeout_jiffies);
+out_free_trans:
+	gsi_trans_free(trans);
+
+	return ret ? ret : remaining ? 0 : -ETIMEDOUT;
+}
+
+/* Return a channel's next completed transaction (or NULL) */
+void gsi_trans_complete(struct gsi_trans *trans)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	enum dma_data_direction direction;
+
+	direction = channel->toward_ipa ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+
+	dma_unmap_sg(trans->dev, trans->sgl, trans->sgc, direction);
+
+	ipa_gsi_trans_complete(trans);
+
+	complete(&trans->completion);
+
+	gsi_trans_free(trans);
+}
+
+/* Cancel a channel's pending transactions */
+void gsi_channel_trans_cancel_pending(struct gsi_channel *channel)
+{
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+	u32 evt_ring_id = channel->evt_ring_id;
+	struct gsi *gsi = channel->gsi;
+	struct gsi_trans *trans;
+	struct gsi_ring *ring;
+
+	ring = &gsi->evt_ring[evt_ring_id].ring;
+
+	spin_lock_bh(&trans_info->spinlock);
+
+	list_for_each_entry(trans, &trans_info->pending, links)
+		trans->result = -ECANCELED;
+
+	list_splice_tail_init(&trans_info->pending, &trans_info->complete);
+
+	spin_unlock_bh(&trans_info->spinlock);
+
+	/* Schedule NAPI polling to complete the cancelled transactions */
+	napi_schedule(&channel->napi);
+}
+
+/* Initialize a channel's GSI transaction info */
+int gsi_channel_trans_init(struct gsi_channel *channel)
+{
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+	u32 tre_count = channel->data->tre_count;
+
+	trans_info->map = kcalloc(tre_count, sizeof(*trans_info->map),
+				  GFP_KERNEL);
+	if (!trans_info->map)
+		return -ENOMEM;
+
+	/* We will never need more transactions than there are TRE
+	 * entries in the transfer ring.  For that reason, we can
+	 * preallocate an array of (at least) that many transactions,
+	 * and use a single free index to determine the next one
+	 * available for allocation.
+	 */
+	trans_info->pool_count = tre_count;
+	trans_info->pool = kcalloc(trans_info->pool_count,
+				   sizeof(*trans_info->pool), GFP_KERNEL);
+	if (!trans_info->pool)
+		goto err_free_map;
+	/* If we get extra memory from the allocator, use it */
+	trans_info->pool_count =
+		ksize(trans_info->pool) / sizeof(*trans_info->pool);
+	trans_info->pool_free = 0;
+
+	/* While transactions are allocated one at a time, a transaction
+	 * can have multiple TREs.  The number of TRE entries in a single
+	 * transaction is limited by the number of TLV FIFO entries the
+	 * channel has.  We reserve TREs when a transaction is allocated,
+	 * but we don't actually use/fill them until the transaction is
+	 * committed.
+	 *
+	 * A transaction uses a scatterlist array to represent the data
+	 * transfers implemented by the transaction.  Each scatterlist
+	 * element is used to fill a single TRE when the transaction is
+	 * committed.  As a result, we need the same number of scatterlist
+	 * elements as there are TREs in the transfer ring, and we can
+	 * preallocate them in a pool.
+	 *
+	 * If we allocate a few (tlv_count - 1) extra entries in our pool,
+	 * we can always satisfy requests without ever worrying about
+	 * straddling the end of the array.  If there aren't enough
+	 * entries starting at the free index, we just allocate free
+	 * entries from the beginning of the pool.
+	 */
+	trans_info->sg_pool_count = tre_count + channel->data->tlv_count - 1;
+	trans_info->sg_pool = kcalloc(trans_info->sg_pool_count,
+				      sizeof(*trans_info->sg_pool), GFP_KERNEL);
+	if (!trans_info->sg_pool)
+		goto err_free_pool;
+	/* Use any extra memory we get from the allocator */
+	trans_info->sg_pool_count =
+		ksize(trans_info->sg_pool) / sizeof(*trans_info->sg_pool);
+	trans_info->sg_pool_free = 0;
+
+	/* The tre_avail field limits the number of outstanding transactions.
+	 * In theory we should be able use all of the TREs in the ring.  But
+	 * in practice, doing that caused the hardware to report running out
+	 * of event ring slots for writing completion information.  So give
+	 * the poor hardware a break, and allow one less than the maximum.
+	 */
+	atomic_set(&trans_info->tre_avail, tre_count - 1);
+
+	spin_lock_init(&trans_info->spinlock);
+	INIT_LIST_HEAD(&trans_info->alloc);
+	INIT_LIST_HEAD(&trans_info->pending);
+	INIT_LIST_HEAD(&trans_info->complete);
+	INIT_LIST_HEAD(&trans_info->polled);
+
+	return 0;
+
+err_free_pool:
+	kfree(trans_info->pool);
+err_free_map:
+	kfree(trans_info->map);
+
+	return -ENOMEM;
+}
+
+/* Inverse of gsi_channel_trans_init() */
+void gsi_channel_trans_exit(struct gsi_channel *channel)
+{
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+
+	kfree(trans_info->sg_pool);
+	kfree(trans_info->pool);
+	kfree(trans_info->map);
+}
diff --git a/drivers/net/ipa/gsi_trans.h b/drivers/net/ipa/gsi_trans.h
new file mode 100644
index 000000000000..2d5a199e4396
--- /dev/null
+++ b/drivers/net/ipa/gsi_trans.h
@@ -0,0 +1,116 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/* Copyright (c) 2012-2018, The Linux Foundation. All rights reserved.
+ * Copyright (C) 2019 Linaro Ltd.
+ */
+#ifndef _GSI_TRANS_H_
+#define _GSI_TRANS_H_
+
+#include <linux/types.h>
+#include <linux/refcount.h>
+#include <linux/completion.h>
+
+struct scatterlist;
+struct device;
+
+struct gsi;
+struct gsi_trans;
+enum ipa_cmd_opcode;
+
+struct gsi_trans {
+	struct list_head links;		/* gsi_channel lists */
+
+	struct gsi *gsi;
+	u32 channel_id;
+
+	u32 tre_count;			/* # TREs requested */
+	u32 len;			/* total # bytes in sgl */
+	struct scatterlist *sgl;
+	u32 sgc;			/* # entries in sgl[] */
+
+	struct completion completion;
+	refcount_t refcount;
+
+	/* fields above are internal only */
+
+	struct device *dev;		/* Use this for DMA mapping */
+	long result;			/* RX count, 0, or error code */
+
+	u64 byte_count;			/* channel byte_count when committed */
+	u64 trans_count;		/* channel trans_count when committed */
+
+	void *data;
+};
+
+/**
+ * gsi_channel_trans_alloc() - Allocate a GSI transaction on a channel
+ * @gsi:	GSI pointer
+ * @channel_id:	Channel the transaction is associated with
+ * @tre_count:	Number of elements in the transaction
+ *
+ * @Return:	A GSI transaction structure, or a null pointer if all
+ *		available transactions are in use
+ */
+struct gsi_trans *gsi_channel_trans_alloc(struct gsi *gsi, u32 channel_id,
+					  u32 tre_count);
+
+/**
+ * gsi_trans_free() - Free a previously-allocated GSI transaction
+ * @trans:	Transaction to be freed
+ *
+ * Note: this should only be used in error paths, before the transaction is
+ * committed or in the event committing the transaction produces an error.
+ * Successfully committing a transaction passes ownership of the structure
+ * to the core transaction code.
+ */
+void gsi_trans_free(struct gsi_trans *trans);
+
+/**
+ * gsi_trans_commit() - Commit a GSI transaction
+ * @trans:	Transaction to commit
+ * @ring_db:	Whether to tell the hardware about these queued transfers
+ * @callback:	Function called when transaction has completed.
+ */
+int gsi_trans_commit(struct gsi_trans *trans, bool ring_db);
+
+/**
+ * gsi_trans_commit_command() - Commit a GSI command transaction and wait
+ *				wait for it to complete
+ * @trans:	Transaction to commit
+ */
+int gsi_trans_commit_command(struct gsi_trans *trans,
+			     enum ipa_cmd_opcode opcode);
+
+/**
+ * gsi_trans_commit_command_timeout() - Commit a GSI command transaction,
+ *					wait for it to complete, with timeout
+ * @trans:	Transaction to commit
+ * @ring_db:	Whether to tell the hardware about these queued transfers
+ * @timeout:	Timeout period (in milliseconds)
+ */
+int gsi_trans_commit_command_timeout(struct gsi_trans *trans,
+				     enum ipa_cmd_opcode opcode,
+				     unsigned long timeout);
+
+/**
+ * gsi_trans_read_byte() - Issue a single byte read TRE on a channel
+ * @gsi:	GSI pointer
+ * @channel_id:	Channel on which to read a byte
+ * @addr:	DMA address into which to transfer the one byte
+ *
+ * This is not a transaction operation at all.  It's defined here because
+ * it needs to be done in coordination with other transaction activity.
+ */
+int gsi_trans_read_byte(struct gsi *gsi, u32 channel_id, dma_addr_t addr);
+
+/**
+ * gsi_trans_read_byte_done() - Clean up after a single byte read TRE
+ * @gsi:	GSI pointer
+ * @channel_id:	Channel on which byte was read
+ *
+ * This function needs to be called to signal that the work related
+ * to reading a byte initiated by gsi_trans_read_byte() is complete.
+ */
+void gsi_trans_read_byte_done(struct gsi *gsi, u32 channel_id);
+
+#endif /* _GSI_TRANS_H_ */