Merge branch 'ipa-transaction-IDs'

Alex Elder says:

====================
net: ipa: start using transaction IDs

A previous group of patches added ID fields to track the state of
transactions:
  https://lore.kernel.org/netdev/20220831224017.377745-1-elder@linaro.org

This series starts using those IDs instead of the lists used
previously.  Most of this series involves reworking the function
that determines which transaction is the "last", which determines
when a channel has been quiesed.  The last patch is mainly used to
prove that the new index method of tracking transaction state is
equivalent to the previous use of lists.
====================

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

3 files changed, 79 insertions, 58 deletions

diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index 9e307eebd33f9..16df699009a86 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -710,43 +710,32 @@ static void gsi_evt_ring_program(struct gsi *gsi, u32 evt_ring_id)
 static struct gsi_trans *gsi_channel_trans_last(struct gsi_channel *channel)
 {
 	struct gsi_trans_info *trans_info = &channel->trans_info;
-	const struct list_head *list;
+	u32 pending_id = trans_info->pending_id;
 	struct gsi_trans *trans;
-
-	spin_lock_bh(&trans_info->spinlock);
-
-	/* There is a small chance a TX transaction got allocated just
-	 * before we disabled transmits, so check for that.
-	 */
-	if (channel->toward_ipa) {
-		list = &trans_info->alloc;
-		if (!list_empty(list))
-			goto done;
-		list = &trans_info->committed;
-		if (!list_empty(list))
-			goto done;
-		list = &trans_info->pending;
-		if (!list_empty(list))
-			goto done;
+	u16 trans_id;
+
+	if (channel->toward_ipa && pending_id != trans_info->free_id) {
+		/* There is a small chance a TX transaction got allocated
+		 * just before we disabled transmits, so check for that.
+		 * The last allocated, committed, or pending transaction
+		 * precedes the first free transaction.
+		 */
+		trans_id = trans_info->free_id - 1;
+	} else if (trans_info->polled_id != pending_id) {
+		/* Otherwise (TX or RX) we want to wait for anything that
+		 * has completed, or has been polled but not released yet.
+		 *
+		 * The last completed or polled transaction precedes the
+		 * first pending transaction.
+		 */
+		trans_id = pending_id - 1;
+	} else {
+		return NULL;
 	}
 
-	/* Otherwise (TX or RX) we want to wait for anything that
-	 * has completed, or has been polled but not released yet.
-	 */
-	list = &trans_info->complete;
-	if (!list_empty(list))
-		goto done;
-	list = &trans_info->polled;
-	if (list_empty(list))
-		list = NULL;
-done:
-	trans = list ? list_last_entry(list, struct gsi_trans, links) : NULL;
-
 	/* Caller will wait for this, so take a reference */
-	if (trans)
-		refcount_inc(&trans->refcount);
-
-	spin_unlock_bh(&trans_info->spinlock);
+	trans = &trans_info->trans[trans_id % channel->tre_count];
+	refcount_inc(&trans->refcount);
 
 	return trans;
 }
diff --git a/drivers/net/ipa/gsi_private.h b/drivers/net/ipa/gsi_private.h
index 0b2516fa21b5d..51bbc7a40dc2d 100644
--- a/drivers/net/ipa/gsi_private.h
+++ b/drivers/net/ipa/gsi_private.h
@@ -17,6 +17,20 @@ struct gsi_channel;
 #define GSI_RING_ELEMENT_SIZE	16	/* bytes; must be a power of 2 */
 
 /**
+ * list_last_entry_or_null - get the last element from a list
+ * @ptr:	the list head to take the element from.
+ * @type:	the type of the struct this is embedded in.
+ * @member:	the name of the list_head within the struct.
+ *
+ * Note that if the list is empty, it returns NULL.
+ */
+#define list_last_entry_or_null(ptr, type, member) ({ \
+	struct list_head *head__ = (ptr); \
+	struct list_head *pos__ = READ_ONCE(head__->prev); \
+	pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
+})
+
+/**
  * gsi_trans_move_complete() - Mark a GSI transaction completed
  * @trans:	Transaction to commit
  */
diff --git a/drivers/net/ipa/gsi_trans.c b/drivers/net/ipa/gsi_trans.c
index 4eef1480c2005..05ab4d052c68b 100644
--- a/drivers/net/ipa/gsi_trans.c
+++ b/drivers/net/ipa/gsi_trans.c
@@ -237,8 +237,24 @@ gsi_channel_trans_mapped(struct gsi_channel *channel, u32 index)
 /* 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);
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+	u16 trans_id = trans_info->completed_id;
+	struct gsi_trans *trans;
+
+	trans = list_first_entry_or_null(&trans_info->complete,
+					 struct gsi_trans, links);
+
+	if (!trans) {
+		WARN_ON(trans_id != trans_info->pending_id);
+		return NULL;
+	}
+
+	if (!WARN_ON(trans_id == trans_info->pending_id)) {
+		trans_id %= channel->tre_count;
+		WARN_ON(trans != &trans_info->trans[trans_id]);
+	}
+
+	return trans;
 }
 
 /* Move a transaction from the allocated list to the committed list */
@@ -309,23 +325,15 @@ 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 */
@@ -413,11 +421,8 @@ struct gsi_trans *gsi_channel_trans_alloc(struct gsi *gsi, u32 channel_id,
 /* 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 */
@@ -433,9 +438,6 @@ 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)
@@ -456,14 +458,6 @@ void gsi_trans_free(struct gsi_trans *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.
 	 */
@@ -712,6 +706,8 @@ void gsi_channel_trans_cancel_pending(struct gsi_channel *channel)
 {
 	struct gsi_trans_info *trans_info = &channel->trans_info;
 	struct gsi_trans *trans;
+	struct gsi_trans *first;
+	struct gsi_trans *last;
 	bool cancelled;
 
 	/* channel->gsi->mutex is held by caller */
@@ -723,11 +719,33 @@ void gsi_channel_trans_cancel_pending(struct gsi_channel *channel)
 
 	list_splice_tail_init(&trans_info->pending, &trans_info->complete);
 
+	first = list_first_entry_or_null(&trans_info->complete,
+					 struct gsi_trans, links);
+	last = list_last_entry_or_null(&trans_info->complete,
+				       struct gsi_trans, links);
+
 	spin_unlock_bh(&trans_info->spinlock);
 
+	/* All pending transactions are now completed */
+	WARN_ON(cancelled != (trans_info->pending_id !=
+				trans_info->committed_id));
+
+	trans_info->pending_id = trans_info->committed_id;
+
 	/* Schedule NAPI polling to complete the cancelled transactions */
-	if (cancelled)
+	if (cancelled) {
+		u16 trans_id;
+
 		napi_schedule(&channel->napi);
+
+		trans_id = trans_info->completed_id;
+		trans = &trans_info->trans[trans_id % channel->tre_count];
+		WARN_ON(trans != first);
+
+		trans_id = trans_info->pending_id - 1;
+		trans = &trans_info->trans[trans_id % channel->tre_count];
+		WARN_ON(trans != last);
+	}
 }
 
 /* Issue a command to read a single byte from a channel */