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From:   Mathew King <mathewk@chromium.org>
To:     linux-kernel@vger.kernel.org
Cc:     Jett Rink <jettrink@chromium.org>,
        Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Guenter Roeck <groeck@chromium.org>,
        Mathew King <mathewk@chromium.org>
Subject: [PATCH 1/2] platform/chrome: skip old cros_ec responses
Date:   Wed,  8 Apr 2020 12:16:37 -0600
Message-Id: <20200408181638.184559-1-mathewk@chromium.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Jett Rink <jettrink@chromium.org>

The ISHTP layer can give us old responses that we already gave up on. We
do not want to interpret these old responses as the current response we
are waiting for.

Signed-off-by: Jett Rink <jettrink@chromium.org>
Signed-off-by: Mathew King <mathewk@chromium.org>
---
 drivers/platform/chrome/cros_ec_ishtp.c | 32 ++++++++++++++++++-------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_ishtp.c b/drivers/platform/chrome/cros_ec_ishtp.c
index 93a71e93a2f1..6f90deb5cf55 100644
--- a/drivers/platform/chrome/cros_ec_ishtp.c
+++ b/drivers/platform/chrome/cros_ec_ishtp.c
@@ -48,7 +48,8 @@ static const guid_t cros_ish_guid =
 struct header {
 	u8 channel;
 	u8 status;
-	u8 reserved[2];
+	u8 id;
+	u8 reserved;
 } __packed;
 
 struct cros_ish_out_msg {
@@ -90,6 +91,7 @@ static DECLARE_RWSEM(init_lock);
  * data exceeds this value, we log an error.
  * @size: Actual size of data received from firmware.
  * @error: 0 for success, negative error code for a failure in process_recv().
+ * @expected_id: Expected id for response that we are waiting on.
  * @received: Set to true on receiving a valid firmware	response to host command
  * @wait_queue: Wait queue for host to wait for firmware response.
  */
@@ -98,6 +100,7 @@ struct response_info {
 	size_t max_size;
 	size_t size;
 	int error;
+	u8 expected_id;
 	bool received;
 	wait_queue_head_t wait_queue;
 };
@@ -162,6 +165,7 @@ static int ish_send(struct ishtp_cl_data *client_data,
 		    u8 *out_msg, size_t out_size,
 		    u8 *in_msg, size_t in_size)
 {
+	static u8 current_id;
 	int rv;
 	struct header *out_hdr = (struct header *)out_msg;
 	struct ishtp_cl *cros_ish_cl = client_data->cros_ish_cl;
@@ -174,8 +178,11 @@ static int ish_send(struct ishtp_cl_data *client_data,
 	client_data->response.data = in_msg;
 	client_data->response.max_size = in_size;
 	client_data->response.error = 0;
+	client_data->response.expected_id = ++current_id;
 	client_data->response.received = false;
 
+	out_hdr->id = client_data->response.expected_id;
+
 	rv = ishtp_cl_send(cros_ish_cl, out_msg, out_size);
 	if (rv) {
 		dev_err(cl_data_to_dev(client_data),
@@ -249,17 +256,23 @@ static void process_recv(struct ishtp_cl *cros_ish_cl,
 
 	switch (in_msg->hdr.channel) {
 	case CROS_EC_COMMAND:
-		/* Sanity check */
-		if (!client_data->response.data) {
+		if (client_data->response.received) {
 			dev_err(dev,
-				"Receiving buffer is null. Should be allocated by calling function\n");
-			client_data->response.error = -EINVAL;
-			goto error_wake_up;
+				"Previous firmware message not yet processed\n");
+			goto end_error;
 		}
 
-		if (client_data->response.received) {
+		if (client_data->response.expected_id != in_msg->hdr.id) {
 			dev_err(dev,
-				"Previous firmware message not yet processed\n");
+				"Dropping old response id %d\n",
+				in_msg->hdr.id);
+			goto end_error;
+		}
+
+		/* Sanity check */
+		if (!client_data->response.data) {
+			dev_err(dev,
+				"Receiving buffer is null. Should be allocated by calling function\n");
 			client_data->response.error = -EINVAL;
 			goto error_wake_up;
 		}
@@ -289,9 +302,10 @@ static void process_recv(struct ishtp_cl *cros_ish_cl,
 		memcpy(client_data->response.data,
 		       rb_in_proc->buffer.data, data_len);
 
+error_wake_up:
 		/* Set flag before waking up the caller */
 		client_data->response.received = true;
-error_wake_up:
+
 		/* Wake the calling thread */
 		wake_up_interruptible(&client_data->response.wait_queue);
 
-- 
2.26.0.292.g33ef6b2f38-goog