[PATCH net-next 02/12] net: dsa: qca8K: Move queuing for request frame into the core

[Luke Howard <lukeh@padl.com>]

From: Andrew Lunn <andrew@lunn.ch>

Combine the queuing of the request and waiting for the completion into
one core helper. Add the function dsa_rmu_request() to perform this.

Access to statistics is not a strict request/reply, so the
dsa_rmu_wait_for_completion needs to be kept.

It is also no possible to combine dsa_rmu_request() and
dsa_rmu_wait_for_completion() since we need to avoid the race of
sending the request, receiving a reply, and the completion has not
been reinitialised because the schedule at decided to do other things.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
 drivers/net/dsa/qca/qca8k-8xxx.c | 32 ++++++++++----------------------
 include/net/dsa.h                |  2 ++
 net/dsa/dsa.c                    | 31 +++++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 22 deletions(-)

diff --git a/drivers/net/dsa/qca/qca8k-8xxx.c b/drivers/net/dsa/qca/qca8k-8xxx.c
index fe6fb69b6f92f..4da6094552f1e 100644
--- a/drivers/net/dsa/qca/qca8k-8xxx.c
+++ b/drivers/net/dsa/qca/qca8k-8xxx.c
@@ -337,10 +337,8 @@ static int qca8k_read_eth(struct qca8k_priv *priv, u32 reg, u32 *val, int len)
 	qca8k_mdio_header_fill_seq_num(skb, mgmt_eth_data->seq);
 	mgmt_eth_data->ack = false;
 
-	dev_queue_xmit(skb);
-
-	ret = dsa_inband_wait_for_completion(&mgmt_eth_data->inband,
-					     QCA8K_ETHERNET_TIMEOUT);
+	ret = dsa_inband_request(&mgmt_eth_data->inband, skb,
+				 QCA8K_ETHERNET_TIMEOUT);
 
 	*val = mgmt_eth_data->data[0];
 	if (len > QCA_HDR_MGMT_DATA1_LEN)
@@ -387,10 +385,8 @@ static int qca8k_write_eth(struct qca8k_priv *priv, u32 reg, u32 *val, int len)
 	qca8k_mdio_header_fill_seq_num(skb, mgmt_eth_data->seq);
 	mgmt_eth_data->ack = false;
 
-	dev_queue_xmit(skb);
-
-	ret = dsa_inband_wait_for_completion(&mgmt_eth_data->inband,
-					     QCA8K_ETHERNET_TIMEOUT);
+	ret = dsa_inband_request(&mgmt_eth_data->inband, skb,
+				 QCA8K_ETHERNET_TIMEOUT);
 
 	ack = mgmt_eth_data->ack;
 
@@ -595,10 +591,8 @@ qca8k_phy_eth_busy_wait(struct qca8k_mgmt_eth_data *mgmt_eth_data,
 	qca8k_mdio_header_fill_seq_num(skb, mgmt_eth_data->seq);
 	mgmt_eth_data->ack = false;
 
-	dev_queue_xmit(skb);
-
-	ret = dsa_inband_wait_for_completion(&mgmt_eth_data->inband,
-					     QCA8K_ETHERNET_TIMEOUT);
+	ret = dsa_inband_request(&mgmt_eth_data->inband, skb,
+				 QCA8K_ETHERNET_TIMEOUT);
 
 	ack = mgmt_eth_data->ack;
 
@@ -695,10 +689,8 @@ qca8k_phy_eth_command(struct qca8k_priv *priv, bool read, int phy,
 	qca8k_mdio_header_fill_seq_num(write_skb, mgmt_eth_data->seq);
 	mgmt_eth_data->ack = false;
 
-	dev_queue_xmit(write_skb);
-
-	ret = dsa_inband_wait_for_completion(&mgmt_eth_data->inband,
-					     QCA8K_ETHERNET_TIMEOUT);
+	ret = dsa_inband_request(&mgmt_eth_data->inband, write_skb,
+				 QCA8K_ETHERNET_TIMEOUT);
 
 	ack = mgmt_eth_data->ack;
 
@@ -730,10 +722,8 @@ qca8k_phy_eth_command(struct qca8k_priv *priv, bool read, int phy,
 		qca8k_mdio_header_fill_seq_num(read_skb, mgmt_eth_data->seq);
 		mgmt_eth_data->ack = false;
 
-		dev_queue_xmit(read_skb);
-
-		ret = dsa_inband_wait_for_completion(&mgmt_eth_data->inband,
-						     QCA8K_ETHERNET_TIMEOUT);
+		ret = dsa_inband_request(&mgmt_eth_data->inband, read_skb,
+					 QCA8K_ETHERNET_TIMEOUT);
 
 		ack = mgmt_eth_data->ack;
 
@@ -757,8 +747,6 @@ qca8k_phy_eth_command(struct qca8k_priv *priv, bool read, int phy,
 	qca8k_mdio_header_fill_seq_num(clear_skb, mgmt_eth_data->seq);
 	mgmt_eth_data->ack = false;
 
-	dev_queue_xmit(clear_skb);
-
 	dsa_inband_wait_for_completion(&mgmt_eth_data->inband,
 				       QCA8K_ETHERNET_TIMEOUT);
 
diff --git a/include/net/dsa.h b/include/net/dsa.h
index 9b0c109b3058a..6b5aeb99ec3bb 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -1357,6 +1357,8 @@ struct dsa_inband {
 
 void dsa_inband_init(struct dsa_inband *inband);
 void dsa_inband_complete(struct dsa_inband *inband);
+int dsa_inband_request(struct dsa_inband *inband, struct sk_buff *skb,
+		       int timeout_ms);
 int dsa_inband_wait_for_completion(struct dsa_inband *inband, int timeout_ms);
 
 /* Keep inline for faster access in hot path */
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index dc4e5cdb2f5b2..534e391fac7b5 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -1856,6 +1856,37 @@ int dsa_inband_wait_for_completion(struct dsa_inband *inband, int timeout_ms)
 }
 EXPORT_SYMBOL_GPL(dsa_inband_wait_for_completion);
 
+/* dsa_inband_request - send an inband request frame and wait for the reply.
+ * @inband: inband state for the switch
+ * @skb: request frame; ownership is transferred to this function
+ * @insert_seqno: optional callback to stamp the sequence number into @skb
+ * @resp: buffer to receive the reply payload, or NULL if none is expected
+ * @resp_len: size of @resp in bytes
+ * @timeout_ms: how long to wait for the reply, in milliseconds
+ *
+ * Serialise against other inband operations, transmit @skb and wait for the
+ * matching reply handed back via dsa_inband_complete().
+ *
+ * Return the number of response bytes copied into @resp (0 when no response
+ * is expected) on success, or a negative errno (-EOPNOTSUPP if the conduit
+ * is down, -ETIMEDOUT if no reply arrived, or an error from the completer).
+ *
+ * Cannot use dsa_inband_wait_for_completion() since the completion needs to
+ * be reinitialised before the skb is queued, to avoid races.
+ */
+int dsa_inband_request(struct dsa_inband *inband, struct sk_buff *skb,
+		       int timeout_ms)
+{
+	unsigned long jiffies = msecs_to_jiffies(timeout_ms);
+
+	reinit_completion(&inband->completion);
+
+	dev_queue_xmit(skb);
+
+	return wait_for_completion_timeout(&inband->completion, jiffies);
+}
+EXPORT_SYMBOL_GPL(dsa_inband_request);
+
 static const struct dsa_stubs __dsa_stubs = {
 	.conduit_hwtstamp_validate = __dsa_conduit_hwtstamp_validate,
 };

-- 
2.43.0