[PATCH net-next v2 2/5] net: ipa: rearrange transaction initialization

From: Alex Elder <elder@linaro.org>
To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
	pabeni@redhat.com
Cc: mka@chromium.org, evgreen@chromium.org,
	bjorn.andersson@linaro.org, quic_cpratapa@quicinc.com,
	quic_avuyyuru@quicinc.com, quic_jponduru@quicinc.com,
	quic_subashab@quicinc.com, elder@kernel.org,
	netdev@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH net-next v2 2/5] net: ipa: rearrange transaction initialization
Date: Tue, 19 Jul 2022 13:10:17 -0500	[thread overview]
Message-ID: <20220719181020.372697-3-elder@linaro.org> (raw)
In-Reply-To: <20220719181020.372697-1-elder@linaro.org>

The transaction map is really associated with the transaction pool;
move its definition earlier in the gsi_trans_info structure.

Rearrange initialization in gsi_channel_trans_init() so it
sets the tre_avail value first, then initializes the transaction
pool, and finally allocating the transaction map.

Update comments.

Signed-off-by: Alex Elder <elder@linaro.org>
---
v2: Fixed the misspelling of "outstanding" in two spots.

 drivers/net/ipa/gsi.h       |  3 +-
 drivers/net/ipa/gsi_trans.c | 60 +++++++++++++++++++------------------
 2 files changed, 33 insertions(+), 30 deletions(-)

diff --git a/drivers/net/ipa/gsi.h b/drivers/net/ipa/gsi.h
index 1c8941911069d..c197df64e69a2 100644
--- a/drivers/net/ipa/gsi.h
+++ b/drivers/net/ipa/gsi.h
@@ -82,9 +82,10 @@ struct gsi_trans_pool {
 struct gsi_trans_info {
 	atomic_t tre_avail;		/* TREs available for allocation */
 	struct gsi_trans_pool pool;	/* transaction pool */
+	struct gsi_trans **map;		/* TRE -> transaction map */
+
 	struct gsi_trans_pool sg_pool;	/* scatterlist pool */
 	struct gsi_trans_pool cmd_pool;	/* command payload DMA pool */
-	struct gsi_trans **map;		/* TRE -> transaction map */
 
 	spinlock_t spinlock;		/* protects updates to the lists */
 	struct list_head alloc;		/* allocated, not committed */
diff --git a/drivers/net/ipa/gsi_trans.c b/drivers/net/ipa/gsi_trans.c
index 45572ebb76e95..3f52932e9e413 100644
--- a/drivers/net/ipa/gsi_trans.c
+++ b/drivers/net/ipa/gsi_trans.c
@@ -709,6 +709,7 @@ void gsi_trans_read_byte_done(struct gsi *gsi, u32 channel_id)
 int gsi_channel_trans_init(struct gsi *gsi, u32 channel_id)
 {
 	struct gsi_channel *channel = &gsi->channel[channel_id];
+	u32 tre_count = channel->tre_count;
 	struct gsi_trans_info *trans_info;
 	u32 tre_max;
 	int ret;
@@ -716,30 +717,40 @@ int gsi_channel_trans_init(struct gsi *gsi, u32 channel_id)
 	/* Ensure the size of a channel element is what's expected */
 	BUILD_BUG_ON(sizeof(struct gsi_tre) != GSI_RING_ELEMENT_SIZE);
 
-	/* The map array is used to determine what transaction is associated
-	 * with a TRE that the hardware reports has completed.  We need one
-	 * map entry per TRE.
-	 */
 	trans_info = &channel->trans_info;
-	trans_info->map = kcalloc(channel->tre_count, sizeof(*trans_info->map),
-				  GFP_KERNEL);
-	if (!trans_info->map)
-		return -ENOMEM;
 
-	/* We can't use more TREs than there are available in the ring.
+	/* The tre_avail field is what ultimately limits the number of
+	 * outstanding transactions and their resources.  A transaction
+	 * allocation succeeds only if the TREs available are sufficient
+	 * for what the transaction might need.
+	 */
+	tre_max = gsi_channel_tre_max(channel->gsi, channel_id);
+	atomic_set(&trans_info->tre_avail, tre_max);
+
+	/* We can't use more TREs than the number available in the ring.
 	 * This limits the number of transactions that can be outstanding.
 	 * Worst case is one TRE per transaction (but we actually limit
-	 * it to something a little less than that).  We allocate resources
-	 * for transactions (including transaction structures) based on
-	 * this maximum number.
+	 * it to something a little less than that).  By allocating a
+	 * power-of-two number of transactions we can use an index
+	 * modulo that number to determine the next one that's free.
+	 * Transactions are allocated one at a time.
 	 */
-	tre_max = gsi_channel_tre_max(channel->gsi, channel_id);
-
-	/* Transactions are allocated one at a time. */
 	ret = gsi_trans_pool_init(&trans_info->pool, sizeof(struct gsi_trans),
 				  tre_max, 1);
 	if (ret)
-		goto err_kfree;
+		return -ENOMEM;
+
+	/* A completion event contains a pointer to the TRE that caused
+	 * the event (which will be the last one used by the transaction).
+	 * Each entry in this map records the transaction associated
+	 * with a corresponding completed TRE.
+	 */
+	trans_info->map = kcalloc(tre_count, sizeof(*trans_info->map),
+				  GFP_KERNEL);
+	if (!trans_info->map) {
+		ret = -ENOMEM;
+		goto err_trans_free;
+	}
 
 	/* A transaction uses a scatterlist array to represent the data
 	 * transfers implemented by the transaction.  Each scatterlist
@@ -751,16 +762,7 @@ int gsi_channel_trans_init(struct gsi *gsi, u32 channel_id)
 				  sizeof(struct scatterlist),
 				  tre_max, channel->trans_tre_max);
 	if (ret)
-		goto err_trans_pool_exit;
-
-	/* Finally, the tre_avail field is what ultimately limits the number
-	 * of outstanding transactions and their resources.  A transaction
-	 * allocation succeeds only if the TREs available are sufficient for
-	 * what the transaction might need.  Transaction resource pools are
-	 * sized based on the maximum number of outstanding TREs, so there
-	 * will always be resources available if there are TREs available.
-	 */
-	atomic_set(&trans_info->tre_avail, tre_max);
+		goto err_map_free;
 
 	spin_lock_init(&trans_info->spinlock);
 	INIT_LIST_HEAD(&trans_info->alloc);
@@ -771,10 +773,10 @@ int gsi_channel_trans_init(struct gsi *gsi, u32 channel_id)
 
 	return 0;
 
-err_trans_pool_exit:
-	gsi_trans_pool_exit(&trans_info->pool);
-err_kfree:
+err_map_free:
 	kfree(trans_info->map);
+err_trans_free:
+	gsi_trans_pool_exit(&trans_info->pool);
 
 	dev_err(gsi->dev, "error %d initializing channel %u transactions\n",
 		ret, channel_id);
-- 
2.34.1

