net: ipa: signal when tag transfer completes

There are times, such as when the modem crashes, when we issue
commands to clear the IPA hardware pipeline.  These commands include
a data transfer command that delivers a small packet directly to the
default (AP<-LAN RX) endpoint.

The places that do this wait for the transactions that contain these
commands to complete, but the pipeline can't be assumed clear until
the sent packet has been *received*.

The small transfer will be delivered with a status structure, and
that status will indicate its tag is valid.  This is the only place
we send a tagged packet, so we use the tag to determine when the
pipeline clear packet has arrived.

Add a completion to the IPA structure to to be used to signal
the receipt of a pipeline clear packet.  Create a new function
ipa_cmd_pipeline_clear_wait() that will wait for that completion.

Reinitialize the completion whenever pipeline clear commands are
added to a transaction.  Extend ipa_endpoint_status_tag() to check
whether a packet whose status contains a valid tag was sent from the
AP->command TX endpoint, and if so, signal the new IPA completion.

Have all callers of ipa_cmd_pipeline_clear_add() wait for the
pipeline clear indication after the transaction that clears the
pipeline has completed.
Signed-off-by: Alex Elder <elder@linaro.org>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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;

drivers/net/ipa/ipa_cmd.c

@@ -573,6 +573,9 @@ void ipa_cmd_pipeline_clear_add(struct gsi_trans *trans)
 	struct ipa *ipa = container_of(trans->gsi, struct ipa, gsi);
 	struct ipa_endpoint *endpoint;
 
+	/* 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);
 
@@ -596,6 +599,11 @@ u32 ipa_cmd_pipeline_clear_count(void)
 	return 4;
 }
 
+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_pipeline_clear_count();
@@ -605,6 +613,7 @@ void ipa_cmd_pipeline_clear(struct ipa *ipa)
 	if (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);

drivers/net/ipa/ipa_cmd.h

@@ -170,8 +170,15 @@ void ipa_cmd_pipeline_clear_add(struct gsi_trans *trans);
  */
 u32 ipa_cmd_pipeline_clear_count(void);
 
+/**
+ * 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_pipeline_clear(struct ipa *ipa);
 

drivers/net/ipa/ipa_endpoint.c

@@ -436,6 +436,8 @@ int ipa_endpoint_modem_exception_reset_all(struct ipa *ipa)
 	/* XXX This should have a 1 second timeout */
 	gsi_trans_commit_wait(trans);
 
+	ipa_cmd_pipeline_clear_wait(ipa);
+
 	return 0;
 }
 
@@ -1178,7 +1180,30 @@ static bool ipa_endpoint_status_skip(struct ipa_endpoint *endpoint,
 static bool ipa_endpoint_status_tag(struct ipa_endpoint *endpoint,
 				    const struct ipa_status *status)
 {
-	return !!le16_get_bits(status->mask, IPA_STATUS_MASK_TAG_VALID_FMASK);
+	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 */

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)