Merge branch 'net-ipa-transaction-state-IDs'

Alex Elder says:

====================
net: ipa: use IDs to track transaction state

This series is the first of three groups of changes that simplify
the way the IPA driver tracks the state of its transactions.

Each GSI channel has a fixed number of transactions allocated at
initialization time.  The number allocated matches the number of
TREs in the transfer ring associated with the channel.  This is
because the transfer ring limits the number of transfers that can
ever be underway, and in the worst case, each transaction represents
a single TRE.

Transactions go through various states during their lifetime.
Currently a set of lists keeps track of which transactions are in
each state.  Initially, all transactions are free.  An allocated
transaction is placed on the allocated list.  Once an allocated
transaction is committed, it is moved from the allocated to the
committed list.  When a committed transaction is sent to hardware
(via a doorbell) it is moved to the pending list.  When hardware
signals that some work has completed, transactions are moved to the
completed list.  Finally, when a completed transaction is polled
it's moved to the polled list before being removed when it becomes
free.

Changing a transaction's state thus normally involves manipulating
two lists, and to prevent corruption a spinlock is held while the
lists are updated.

Transactions move through their states in a well-defined sequence
though, and they do so strictly in order.  So transaction 0 is
always allocated before transaction 1; transaction 0 is always
committed before transaction 1; and so on, through completion,
polling, and becoming free.  Because of this, it's sufficient to
just keep track of which transaction is the first in each state.
The rest of the transactions in a given state can be derived from
the first transaction in an "adjacent" state.  As a result, we can
track the state of all transactions with a set of indexes, and can
update these without the need for a spinlock.

This first group of patches just defines the set of indexes that
will be used for this new way of tracking transaction state.  Two
more groups of patches will follow.  I've broken the 17 patches into
these three groups to facilitate review.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 84 insertions, 14 deletions

diff --git a/drivers/net/ipa/gsi.h b/drivers/net/ipa/gsi.h
index 23de5f67374c..13468704c400 100644
--- a/drivers/net/ipa/gsi.h
+++ b/drivers/net/ipa/gsi.h
@@ -82,7 +82,14 @@ struct gsi_trans_pool {
 
 struct gsi_trans_info {
 	atomic_t tre_avail;		/* TREs available for allocation */
-	struct gsi_trans_pool pool;	/* transaction pool */
+
+	u16 free_id;			/* first free trans in array */
+	u16 allocated_id;		/* first allocated transaction */
+	u16 committed_id;		/* first committed transaction */
+	u16 pending_id;			/* first pending transaction */
+	u16 completed_id;		/* first completed transaction */
+	u16 polled_id;			/* first polled transaction */
+	struct gsi_trans *trans;	/* transaction array */
 	struct gsi_trans **map;		/* TRE -> transaction map */
 
 	struct gsi_trans_pool sg_pool;	/* scatterlist pool */
diff --git a/drivers/net/ipa/gsi_trans.c b/drivers/net/ipa/gsi_trans.c
index 18e7e8c405be..4eef1480c200 100644
--- a/drivers/net/ipa/gsi_trans.c
+++ b/drivers/net/ipa/gsi_trans.c
@@ -252,6 +252,9 @@ static void gsi_trans_move_committed(struct gsi_trans *trans)
 	list_move_tail(&trans->links, &trans_info->committed);
 
 	spin_unlock_bh(&trans_info->spinlock);
+
+	/* This allocated transaction is now committed */
+	trans_info->allocated_id++;
 }
 
 /* Move transactions from the committed list to the pending list */
@@ -259,7 +262,9 @@ 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;
+	u16 trans_index = trans - &trans_info->trans[0];
 	struct list_head list;
+	u16 delta;
 
 	spin_lock_bh(&trans_info->spinlock);
 
@@ -268,6 +273,10 @@ static void gsi_trans_move_pending(struct gsi_trans *trans)
 	list_splice_tail(&list, &trans_info->pending);
 
 	spin_unlock_bh(&trans_info->spinlock);
+
+	/* These committed transactions are now pending */
+	delta = trans_index - trans_info->committed_id + 1;
+	trans_info->committed_id += delta % channel->tre_count;
 }
 
 /* Move a transaction and all of its predecessors from the pending list
@@ -277,7 +286,9 @@ 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;
+	u16 trans_index = trans - trans_info->trans;
 	struct list_head list;
+	u16 delta;
 
 	spin_lock_bh(&trans_info->spinlock);
 
@@ -286,6 +297,11 @@ void gsi_trans_move_complete(struct gsi_trans *trans)
 	list_splice_tail(&list, &trans_info->complete);
 
 	spin_unlock_bh(&trans_info->spinlock);
+
+	/* These pending transactions are now completed */
+	delta = trans_index - trans_info->pending_id + 1;
+	delta %= channel->tre_count;
+	trans_info->pending_id += delta;
 }
 
 /* Move a transaction from the completed list to the polled list */
@@ -293,12 +309,23 @@ 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;
+	u16 trans_index;
 
 	spin_lock_bh(&trans_info->spinlock);
 
 	list_move_tail(&trans->links, &trans_info->polled);
 
+	trans = list_first_entry(&trans_info->polled,
+				 struct gsi_trans, links);
+
 	spin_unlock_bh(&trans_info->spinlock);
+
+	/* This completed transaction is now polled */
+	trans_info->completed_id++;
+
+	WARN_ON(trans_info->polled_id == trans_info->completed_id);
+	trans_index = trans_info->polled_id % channel->tre_count;
+	WARN_ON(trans != &trans_info->trans[trans_index]);
 }
 
 /* Reserve some number of TREs on a channel.  Returns true if successful */
@@ -343,20 +370,22 @@ struct gsi_trans *gsi_channel_trans_alloc(struct gsi *gsi, u32 channel_id,
 	struct gsi_channel *channel = &gsi->channel[channel_id];
 	struct gsi_trans_info *trans_info;
 	struct gsi_trans *trans;
+	u16 trans_index;
 
 	if (WARN_ON(tre_count > channel->trans_tre_max))
 		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 we can't reserve the TREs for the transaction, we're done */
 	if (!gsi_trans_tre_reserve(trans_info, tre_count))
 		return NULL;
 
-	/* Allocate and initialize non-zero fields in the transaction */
-	trans = gsi_trans_pool_alloc(&trans_info->pool, 1);
+	trans_index = trans_info->free_id % channel->tre_count;
+	trans = &trans_info->trans[trans_index];
+	memset(trans, 0, sizeof(*trans));
+
+	/* Initialize non-zero fields in the transaction */
 	trans->gsi = gsi;
 	trans->channel_id = channel_id;
 	trans->rsvd_count = tre_count;
@@ -367,6 +396,10 @@ struct gsi_trans *gsi_channel_trans_alloc(struct gsi *gsi, u32 channel_id,
 	sg_init_marker(trans->sgl, tre_count);
 
 	trans->direction = direction;
+	refcount_set(&trans->refcount, 1);
+
+	/* This free transaction will now be allocated */
+	trans_info->free_id++;
 
 	spin_lock_bh(&trans_info->spinlock);
 
@@ -374,16 +407,17 @@ struct gsi_trans *gsi_channel_trans_alloc(struct gsi *gsi, u32 channel_id,
 
 	spin_unlock_bh(&trans_info->spinlock);
 
-	refcount_set(&trans->refcount, 1);
-
 	return trans;
 }
 
 /* Free a previously-allocated transaction */
 void gsi_trans_free(struct gsi_trans *trans)
 {
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
 	refcount_t *refcount = &trans->refcount;
 	struct gsi_trans_info *trans_info;
+	struct gsi_trans *polled;
+	u16 trans_index;
 	bool last;
 
 	/* We must hold the lock to release the last reference */
@@ -399,13 +433,36 @@ void gsi_trans_free(struct gsi_trans *trans)
 	if (last)
 		list_del(&trans->links);
 
+	polled = list_first_entry_or_null(&trans_info->polled,
+					  struct gsi_trans, links);
+
 	spin_unlock_bh(&trans_info->spinlock);
 
 	if (!last)
 		return;
 
-	if (trans->used_count)
+	/* Unused transactions are allocated but never committed, pending,
+	 * completed, or polled.
+	 */
+	if (!trans->used_count) {
+		trans_info->allocated_id++;
+		trans_info->committed_id++;
+		trans_info->pending_id++;
+		trans_info->completed_id++;
+	} else {
 		ipa_gsi_trans_release(trans);
+	}
+
+	/* This transaction is now free */
+	trans_info->polled_id++;
+
+	if (polled) {
+		trans_index = trans_info->polled_id % channel->tre_count;
+		WARN_ON(polled != &trans_info->trans[trans_index]);
+	} else {
+		WARN_ON(trans_info->polled_id !=
+			trans_info->completed_id);
+	}
 
 	/* Releasing the reserved TREs implicitly frees the sgl[] and
 	 * (if present) info[] arrays, plus the transaction itself.
@@ -736,10 +793,16 @@ int gsi_channel_trans_init(struct gsi *gsi, u32 channel_id)
 	 * modulo that number to determine the next one that's free.
 	 * Transactions are allocated one at a time.
 	 */
-	ret = gsi_trans_pool_init(&trans_info->pool, sizeof(struct gsi_trans),
-				  tre_max, 1);
-	if (ret)
+	trans_info->trans = kcalloc(tre_count, sizeof(*trans_info->trans),
+				    GFP_KERNEL);
+	if (!trans_info->trans)
 		return -ENOMEM;
+	trans_info->free_id = 0;	/* all modulo channel->tre_count */
+	trans_info->allocated_id = 0;
+	trans_info->committed_id = 0;
+	trans_info->pending_id = 0;
+	trans_info->completed_id = 0;
+	trans_info->polled_id = 0;
 
 	/* A completion event contains a pointer to the TRE that caused
 	 * the event (which will be the last one used by the transaction).
@@ -777,7 +840,7 @@ int gsi_channel_trans_init(struct gsi *gsi, u32 channel_id)
 err_map_free:
 	kfree(trans_info->map);
 err_trans_free:
-	gsi_trans_pool_exit(&trans_info->pool);
+	kfree(trans_info->trans);
 
 	dev_err(gsi->dev, "error %d initializing channel %u transactions\n",
 		ret, channel_id);
@@ -791,6 +854,6 @@ void gsi_channel_trans_exit(struct gsi_channel *channel)
 	struct gsi_trans_info *trans_info = &channel->trans_info;
 
 	gsi_trans_pool_exit(&trans_info->sg_pool);
-	gsi_trans_pool_exit(&trans_info->pool);
+	kfree(trans_info->trans);
 	kfree(trans_info->map);
 }