net: ipa: rename "tag status" symbols

There is a set of functions and symbols related to performing
"tag_process" immediate commands to clear the IPA pipeline.  The
name is related to one of the commands issued when doing this, but
it doesn't really convey the overall purpose of taking this action.

The purpose is to take some steps to "clear out" the hardware
pipeline, and to wait until that process completes, to ensure the
IPA hardware is in a well-defined state.

Rename these symbols to use "pipeline_clear" in their names instead.
Add some comments to explain a bit more about what's going on.

Signed-off-by: Alex Elder <elder@linaro.org>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 18 insertions, 8 deletions

diff --git a/drivers/net/ipa/ipa_cmd.c b/drivers/net/ipa/ipa_cmd.c
index 002e51448510..27630244512d 100644
--- a/drivers/net/ipa/ipa_cmd.c
+++ b/drivers/net/ipa/ipa_cmd.c
@@ -567,33 +567,43 @@ 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];
-
+	/* 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 contain the given tag 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);
 }
 
-/* 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(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);
 	} else {
 		dev_err(&ipa->pdev->dev,