Subject: [PATCH net v2 3/3] net: ipa: prevent concurrent replenish

From: Alex Elder <[email-masked]>
Date: Wed, 12 Jan 2022 07:30:12 -0600

We have seen cases where an endpoint RX completion interrupt arrives
while replenishing for the endpoint is underway.  This causes another
instance of replenishing to begin as part of completing the receive
transaction.  If this occurs it can lead to transaction corruption.

Use a new flag to ensure only one replenish instance for an endpoint
executes at a time.

Fixes: 84f9bd12d46db ("soc: qcom: ipa: IPA endpoints")
Signed-off-by: Alex Elder <[email-masked]>
---
v2: Use test_and_set_bit() and clear_bit(), as Jakub suggested

 drivers/net/ipa/ipa_endpoint.c | 13 +++++++++++++
 drivers/net/ipa/ipa_endpoint.h |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index cddddcedaf72b..68291a3efd040 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -1088,15 +1088,27 @@ static void ipa_endpoint_replenish(struct ipa_endpoint *endpoint, bool add_one)
 		return;
 	}
 
+	/* If already active, just update the backlog */
+	if (test_and_set_bit(IPA_REPLENISH_ACTIVE, endpoint->replenish_flags)) {
+		if (add_one)
+			atomic_inc(&endpoint->replenish_backlog);
+		return;
+	}
+
 	while (atomic_dec_not_zero(&endpoint->replenish_backlog))
 		if (ipa_endpoint_replenish_one(endpoint))
 			goto try_again_later;
+
+	clear_bit(IPA_REPLENISH_ACTIVE, endpoint->replenish_flags);
+
 	if (add_one)
 		atomic_inc(&endpoint->replenish_backlog);
 
 	return;
 
 try_again_later:
+	clear_bit(IPA_REPLENISH_ACTIVE, endpoint->replenish_flags);
+
 	/* The last one didn't succeed, so fix the backlog */
 	delta = add_one ? 2 : 1;
 	backlog = atomic_add_return(delta, &endpoint->replenish_backlog);
@@ -1691,6 +1703,7 @@ static void ipa_endpoint_setup_one(struct ipa_endpoint *endpoint)
 		 * backlog is the same as the maximum outstanding TREs.
 		 */
 		clear_bit(IPA_REPLENISH_ENABLED, endpoint->replenish_flags);
+		clear_bit(IPA_REPLENISH_ACTIVE, endpoint->replenish_flags);
 		atomic_set(&endpoint->replenish_saved,
 			   gsi_channel_tre_max(gsi, endpoint->channel_id));
 		atomic_set(&endpoint->replenish_backlog, 0);
diff --git a/drivers/net/ipa/ipa_endpoint.h b/drivers/net/ipa/ipa_endpoint.h
index 07d5c20e5f000..0313cdc607de3 100644
--- a/drivers/net/ipa/ipa_endpoint.h
+++ b/drivers/net/ipa/ipa_endpoint.h
@@ -44,10 +44,12 @@ enum ipa_endpoint_name {
  * enum ipa_replenish_flag:	RX buffer replenish flags
  *
  * @IPA_REPLENISH_ENABLED:	Whether receive buffer replenishing is enabled
+ * @IPA_REPLENISH_ACTIVE:	Whether replenishing is underway
  * @IPA_REPLENISH_COUNT:	Number of defined replenish flags
  */
 enum ipa_replenish_flag {
 	IPA_REPLENISH_ENABLED,
+	IPA_REPLENISH_ACTIVE,
 	IPA_REPLENISH_COUNT,	/* Number of flags (must be last) */
 };
 
-- 
2.32.0