linux-kernel - [PATCH net 2/2] net: ipa: use tag process on modem crash

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Date:   Thu,  7 May 2020 14:14:04 -0500
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net
Cc:     evgreen@...omium.org.net, subashab@...eaurora.org,
        cpratapa@...eaurora.org, bjorn.andersson@...aro.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net 2/2] net: ipa: use tag process on modem crash

One part of recovering from a modem crash is performing a "tag
sequence" of several IPA immediate commands, to clear the hardware
pipeline.  The sequence ends with a data transfer request on the
command endpoint (which is not otherwise done).  Unfortunately,
attempting to do the data transfer led to a hang, so that request
plus two other commands were commented out.

The previous commit fixes the bug that was causing that hang.  And
with that bug fixed we can properly issue the tag sequence when the
modem crashes, to return the hardware to a known state.

Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ipa/ipa_cmd.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ipa/ipa_cmd.c b/drivers/net/ipa/ipa_cmd.c
index d226b858742d..cee417181f98 100644
--- a/drivers/net/ipa/ipa_cmd.c
+++ b/drivers/net/ipa/ipa_cmd.c
@@ -628,23 +628,15 @@ static void ipa_cmd_transfer_add(struct gsi_trans *trans, u16 size)
 
 void ipa_cmd_tag_process_add(struct gsi_trans *trans)
 {
-	ipa_cmd_register_write_add(trans, 0, 0, 0, true);
-#if 1
-	/* Reference these functions to avoid a compile error */
-	(void)ipa_cmd_ip_packet_init_add;
-	(void)ipa_cmd_ip_tag_status_add;
-	(void) ipa_cmd_transfer_add;
-#else
 	struct ipa *ipa = container_of(trans->gsi, struct ipa, gsi);
-	struct gsi_endpoint *endpoint;
+	struct ipa_endpoint *endpoint;
 
 	endpoint = ipa->name_map[IPA_ENDPOINT_AP_LAN_RX];
+
+	ipa_cmd_register_write_add(trans, 0, 0, 0, true);
 	ipa_cmd_ip_packet_init_add(trans, endpoint->endpoint_id);
-
 	ipa_cmd_ip_tag_status_add(trans, 0xcba987654321);
-
 	ipa_cmd_transfer_add(trans, 4);
-#endif
 }
 
 /* Returns the number of commands required for the tag process */
-- 
2.20.1