Merge branch 'net-ipa-hardware-pipeline-cleanup-fixes'

Alex Elder says:

====================
net: ipa: hardware pipeline cleanup fixes

There is a procedure currently referred to as a "tag process" that
is performed to clear the IPA hardware pipeline--either at the time
of a modem crash, or when suspending modem GSI channels.

One thing done in this procedure is issuing a command that sends a
data packet originating from the AP->command TX endpoint, destined
for the AP<-LAN RX (default) endpoint.  And although we currently
wait for the send to complete, we do *not* wait for the packet to be
received.  But the pipeline can't be assumed clear until we have
actually received this packet.

This series addresses this by detecting when the pipeline-clearing
packet has been received, and using a completion to allow a waiter
to know when that has happened.  This uses the IPA status capability
(which sends an extra status buffer for certain packets).  It also
uses the ability to supply a "tag" with a packet, which will be
delivered with the packet's status buffer.  We tag the data packet
that's sent to clear the pipeline, and use the receipt of a status
buffer associated with a tagged packet to determine when that packet
has arrived.

"Tag status" just desribes one aspect of this procedure, so some
symbols are renamed to be more like "pipeline clear" so they better
describe the larger purpose.  Finally, two functions used in this
code don't use their arguments, so those arguments are removed.
====================

Link: https://lore.kernel.org/r/20210126185703.29087-1-elder@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

5 files changed, 109 insertions, 42 deletions

diff --git a/drivers/net/ipa/ipa.h b/drivers/net/ipa/ipa.h
index c6c6a7f6909c..802077631371 100644
--- a/drivers/net/ipa/ipa.h
+++ b/drivers/net/ipa/ipa.h
@@ -43,6 +43,7 @@ enum ipa_flag {
  * @flags:		Boolean state flags
  * @version:		IPA hardware version
  * @pdev:		Platform device
+ * @completion:		Used to signal pipeline clear transfer complete
  * @smp2p:		SMP2P information
  * @clock:		IPA clocking information
  * @table_addr:		DMA address of filter/route table content
@@ -82,6 +83,7 @@ struct ipa {
 	DECLARE_BITMAP(flags, IPA_FLAG_COUNT);
 	enum ipa_version version;
 	struct platform_device *pdev;
+	struct completion completion;
 	struct notifier_block nb;
 	void *notifier;
 	struct ipa_smp2p *smp2p;
diff --git a/drivers/net/ipa/ipa_cmd.c b/drivers/net/ipa/ipa_cmd.c
index 002e51448510..97b50fee6008 100644
--- a/drivers/net/ipa/ipa_cmd.c
+++ b/drivers/net/ipa/ipa_cmd.c
@@ -529,7 +529,7 @@ void ipa_cmd_dma_shared_mem_add(struct gsi_trans *trans, u32 offset, u16 size,
 			  direction, opcode);
 }
 
-static void ipa_cmd_ip_tag_status_add(struct gsi_trans *trans, u64 tag)
+static void ipa_cmd_ip_tag_status_add(struct gsi_trans *trans)
 {
 	struct ipa *ipa = container_of(trans->gsi, struct ipa, gsi);
 	enum ipa_cmd_opcode opcode = IPA_CMD_IP_PACKET_TAG_STATUS;
@@ -543,14 +543,14 @@ static void ipa_cmd_ip_tag_status_add(struct gsi_trans *trans, u64 tag)
 	cmd_payload = ipa_cmd_payload_alloc(ipa, &payload_addr);
 	payload = &cmd_payload->ip_packet_tag_status;
 
-	payload->tag = u64_encode_bits(tag, IP_PACKET_TAG_STATUS_TAG_FMASK);
+	payload->tag = le64_encode_bits(0, IP_PACKET_TAG_STATUS_TAG_FMASK);
 
 	gsi_trans_cmd_add(trans, payload, sizeof(*payload), payload_addr,
 			  direction, opcode);
 }
 
 /* Issue a small command TX data transfer */
-static void ipa_cmd_transfer_add(struct gsi_trans *trans, u16 size)
+static void ipa_cmd_transfer_add(struct gsi_trans *trans)
 {
 	struct ipa *ipa = container_of(trans->gsi, struct ipa, gsi);
 	enum dma_data_direction direction = DMA_TO_DEVICE;
@@ -558,8 +558,6 @@ static void ipa_cmd_transfer_add(struct gsi_trans *trans, u16 size)
 	union ipa_cmd_payload *payload;
 	dma_addr_t payload_addr;
 
-	/* assert(size <= sizeof(*payload)); */
-
 	/* Just transfer a zero-filled payload structure */
 	payload = ipa_cmd_payload_alloc(ipa, &payload_addr);
 
@@ -567,34 +565,53 @@ static void ipa_cmd_transfer_add(struct gsi_trans *trans, u16 size)
 			  direction, opcode);
 }
 
-void ipa_cmd_tag_process_add(struct gsi_trans *trans)
+/* Add immediate commands to a transaction to clear the hardware pipeline */
+void ipa_cmd_pipeline_clear_add(struct gsi_trans *trans)
 {
 	struct ipa *ipa = container_of(trans->gsi, struct ipa, gsi);
 	struct ipa_endpoint *endpoint;
 
-	endpoint = ipa->name_map[IPA_ENDPOINT_AP_LAN_RX];
+	/* This will complete when the transfer is received */
+	reinit_completion(&ipa->completion);
 
+	/* Issue a no-op register write command (mask 0 means no write) */
 	ipa_cmd_register_write_add(trans, 0, 0, 0, true);
+
+	/* Send a data packet through the IPA pipeline.  The packet_init
+	 * command says to send the next packet directly to the exception
+	 * endpoint without any other IPA processing.  The tag_status
+	 * command requests that status be generated on completion of
+	 * that transfer, and that it will be tagged with a value.
+	 * Finally, the transfer command sends a small packet of data
+	 * (instead of a command) using the command endpoint.
+	 */
+	endpoint = ipa->name_map[IPA_ENDPOINT_AP_LAN_RX];
 	ipa_cmd_ip_packet_init_add(trans, endpoint->endpoint_id);
-	ipa_cmd_ip_tag_status_add(trans, 0xcba987654321);
-	ipa_cmd_transfer_add(trans, 4);
+	ipa_cmd_ip_tag_status_add(trans);
+	ipa_cmd_transfer_add(trans);
 }
 
-/* Returns the number of commands required for the tag process */
-u32 ipa_cmd_tag_process_count(void)
+/* Returns the number of commands required to clear the pipeline */
+u32 ipa_cmd_pipeline_clear_count(void)
 {
 	return 4;
 }
 
-void ipa_cmd_tag_process(struct ipa *ipa)
+void ipa_cmd_pipeline_clear_wait(struct ipa *ipa)
+{
+	wait_for_completion(&ipa->completion);
+}
+
+void ipa_cmd_pipeline_clear(struct ipa *ipa)
 {
-	u32 count = ipa_cmd_tag_process_count();
+	u32 count = ipa_cmd_pipeline_clear_count();
 	struct gsi_trans *trans;
 
 	trans = ipa_cmd_trans_alloc(ipa, count);
 	if (trans) {
-		ipa_cmd_tag_process_add(trans);
+		ipa_cmd_pipeline_clear_add(trans);
 		gsi_trans_commit_wait(trans);
+		ipa_cmd_pipeline_clear_wait(ipa);
 	} else {
 		dev_err(&ipa->pdev->dev,
 			"error allocating %u entry tag transaction\n", count);
diff --git a/drivers/net/ipa/ipa_cmd.h b/drivers/net/ipa/ipa_cmd.h
index 4ed09c486abc..6dd3d35cf315 100644
--- a/drivers/net/ipa/ipa_cmd.h
+++ b/drivers/net/ipa/ipa_cmd.h
@@ -157,26 +157,30 @@ void ipa_cmd_dma_shared_mem_add(struct gsi_trans *trans, u32 offset,
 				u16 size, dma_addr_t addr, bool toward_ipa);
 
 /**
- * ipa_cmd_tag_process_add() - Add IPA tag process commands to a transaction
+ * ipa_cmd_pipeline_clear_add() - Add pipeline clear commands to a transaction
  * @trans:	GSI transaction
  */
-void ipa_cmd_tag_process_add(struct gsi_trans *trans);
+void ipa_cmd_pipeline_clear_add(struct gsi_trans *trans);
 
 /**
- * ipa_cmd_tag_process_add_count() - Number of commands in a tag process
+ * ipa_cmd_pipeline_clear_count() - # commands required to clear pipeline
  *
  * Return:	The number of elements to allocate in a transaction
- *		to hold tag process commands
+ *		to hold commands to clear the pipeline
  */
-u32 ipa_cmd_tag_process_count(void);
+u32 ipa_cmd_pipeline_clear_count(void);
 
 /**
- * ipa_cmd_tag_process() - Perform a tag process
- *
- * @Return:	The number of elements to allocate in a transaction
- *		to hold tag process commands
+ * ipa_cmd_pipeline_clear_wait() - Wait pipeline clear to complete
+ * @ipa:	- IPA pointer
+ */
+void ipa_cmd_pipeline_clear_wait(struct ipa *ipa);
+
+/**
+ * ipa_cmd_pipeline_clear() - Clear the hardware pipeline
+ * @ipa:	- IPA pointer
  */
-void ipa_cmd_tag_process(struct ipa *ipa);
+void ipa_cmd_pipeline_clear(struct ipa *ipa);
 
 /**
  * ipa_cmd_trans_alloc() - Allocate a transaction for the command TX endpoint
diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index 688a3dd40510..8313220d41e7 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -69,8 +69,11 @@ struct ipa_status {
 };
 
 /* Field masks for struct ipa_status structure fields */
+#define IPA_STATUS_MASK_TAG_VALID_FMASK		GENMASK(4, 4)
+#define IPA_STATUS_SRC_IDX_FMASK		GENMASK(4, 0)
 #define IPA_STATUS_DST_IDX_FMASK		GENMASK(4, 0)
 #define IPA_STATUS_FLAGS1_RT_RULE_ID_FMASK	GENMASK(31, 22)
+#define IPA_STATUS_FLAGS2_TAG_FMASK		GENMASK_ULL(63, 16)
 
 #ifdef IPA_VALIDATE
 
@@ -399,7 +402,7 @@ int ipa_endpoint_modem_exception_reset_all(struct ipa *ipa)
 	 * That won't happen, and we could be more precise, but this is fine
 	 * for now.  We need to end the transaction with a "tag process."
 	 */
-	count = hweight32(initialized) + ipa_cmd_tag_process_count();
+	count = hweight32(initialized) + ipa_cmd_pipeline_clear_count();
 	trans = ipa_cmd_trans_alloc(ipa, count);
 	if (!trans) {
 		dev_err(&ipa->pdev->dev,
@@ -428,11 +431,13 @@ int ipa_endpoint_modem_exception_reset_all(struct ipa *ipa)
 		ipa_cmd_register_write_add(trans, offset, 0, ~0, false);
 	}
 
-	ipa_cmd_tag_process_add(trans);
+	ipa_cmd_pipeline_clear_add(trans);
 
 	/* XXX This should have a 1 second timeout */
 	gsi_trans_commit_wait(trans);
 
+	ipa_cmd_pipeline_clear_wait(ipa);
+
 	return 0;
 }
 
@@ -1172,11 +1177,45 @@ static bool ipa_endpoint_status_skip(struct ipa_endpoint *endpoint,
 	return false;	/* Don't skip this packet, process it */
 }
 
+static bool ipa_endpoint_status_tag(struct ipa_endpoint *endpoint,
+				    const struct ipa_status *status)
+{
+	struct ipa_endpoint *command_endpoint;
+	struct ipa *ipa = endpoint->ipa;
+	u32 endpoint_id;
+
+	if (!le16_get_bits(status->mask, IPA_STATUS_MASK_TAG_VALID_FMASK))
+		return false;	/* No valid tag */
+
+	/* The status contains a valid tag.  We know the packet was sent to
+	 * this endpoint (already verified by ipa_endpoint_status_skip()).
+	 * If the packet came from the AP->command TX endpoint we know
+	 * this packet was sent as part of the pipeline clear process.
+	 */
+	endpoint_id = u8_get_bits(status->endp_src_idx,
+				  IPA_STATUS_SRC_IDX_FMASK);
+	command_endpoint = ipa->name_map[IPA_ENDPOINT_AP_COMMAND_TX];
+	if (endpoint_id == command_endpoint->endpoint_id) {
+		complete(&ipa->completion);
+	} else {
+		dev_err(&ipa->pdev->dev,
+			"unexpected tagged packet from endpoint %u\n",
+			endpoint_id);
+	}
+
+	return true;
+}
+
 /* Return whether the status indicates the packet should be dropped */
-static bool ipa_status_drop_packet(const struct ipa_status *status)
+static bool ipa_endpoint_status_drop(struct ipa_endpoint *endpoint,
+				     const struct ipa_status *status)
 {
 	u32 val;
 
+	/* If the status indicates a tagged transfer, we'll drop the packet */
+	if (ipa_endpoint_status_tag(endpoint, status))
+		return true;
+
 	/* Deaggregation exceptions we drop; all other types we consume */
 	if (status->exception)
 		return status->exception == IPA_STATUS_EXCEPTION_DEAGGR;
@@ -1213,12 +1252,11 @@ static void ipa_endpoint_status_parse(struct ipa_endpoint *endpoint,
 			continue;
 		}
 
-		/* Compute the amount of buffer space consumed by the
-		 * packet, including the status element.  If the hardware
-		 * is configured to pad packet data to an aligned boundary,
-		 * account for that.  And if checksum offload is is enabled
-		 * a trailer containing computed checksum information will
-		 * be appended.
+		/* Compute the amount of buffer space consumed by the packet,
+		 * including the status element.  If the hardware is configured
+		 * to pad packet data to an aligned boundary, account for that.
+		 * And if checksum offload is enabled a trailer containing
+		 * computed checksum information will be appended.
 		 */
 		align = endpoint->data->rx.pad_align ? : 1;
 		len = le16_to_cpu(status->pkt_len);
@@ -1226,16 +1264,21 @@ static void ipa_endpoint_status_parse(struct ipa_endpoint *endpoint,
 		if (endpoint->data->checksum)
 			len += sizeof(struct rmnet_map_dl_csum_trailer);
 
-		/* Charge the new packet with a proportional fraction of
-		 * the unused space in the original receive buffer.
-		 * XXX Charge a proportion of the *whole* receive buffer?
-		 */
-		if (!ipa_status_drop_packet(status)) {
-			u32 extra = unused * len / total_len;
-			void *data2 = data + sizeof(*status);
-			u32 len2 = le16_to_cpu(status->pkt_len);
+		if (!ipa_endpoint_status_drop(endpoint, status)) {
+			void *data2;
+			u32 extra;
+			u32 len2;
 
 			/* Client receives only packet data (no status) */
+			data2 = data + sizeof(*status);
+			len2 = le16_to_cpu(status->pkt_len);
+
+			/* Have the true size reflect the extra unused space in
+			 * the original receive buffer.  Distribute the "cost"
+			 * proportionately across all aggregated packets in the
+			 * buffer.
+			 */
+			extra = DIV_ROUND_CLOSEST(unused * len, total_len);
 			ipa_endpoint_skb_copy(endpoint, data2, len2, extra);
 		}
 
@@ -1564,7 +1607,7 @@ void ipa_endpoint_suspend(struct ipa *ipa)
 	if (ipa->modem_netdev)
 		ipa_modem_suspend(ipa->modem_netdev);
 
-	ipa_cmd_tag_process(ipa);
+	ipa_cmd_pipeline_clear(ipa);
 
 	ipa_endpoint_suspend_one(ipa->name_map[IPA_ENDPOINT_AP_LAN_RX]);
 	ipa_endpoint_suspend_one(ipa->name_map[IPA_ENDPOINT_AP_COMMAND_TX]);
diff --git a/drivers/net/ipa/ipa_main.c b/drivers/net/ipa/ipa_main.c
index ab0fd5cb4927..c10e7340b031 100644
--- a/drivers/net/ipa/ipa_main.c
+++ b/drivers/net/ipa/ipa_main.c
@@ -831,6 +831,7 @@ static int ipa_probe(struct platform_device *pdev)
 	dev_set_drvdata(dev, ipa);
 	ipa->clock = clock;
 	ipa->version = data->version;
+	init_completion(&ipa->completion);
 
 	ret = ipa_reg_init(ipa);
 	if (ret)