media: cec: abort if the current transmit was canceled

If a transmit-in-progress was canceled, then, once the transmit
is done, mark it as aborted and refrain from retrying the transmit.

To signal this situation the new transmit_in_progress_aborted field is
set to true.

The old implementation would just set adap->transmitting to NULL and
set adap->transmit_in_progress to false, but on the hardware level
the transmit was still ongoing. However, the framework would think
the transmit was aborted, and if a new transmit was issued, then
it could overwrite the HW buffer containing the old transmit with the
new transmit, leading to garbled data on the CEC bus.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/cec/core/cec-adap.c

@@ -421,7 +421,7 @@ static void cec_flush(struct cec_adapter *adap)
 		cec_data_cancel(data, CEC_TX_STATUS_ABORTED);
 	}
 	if (adap->transmitting)
-		cec_data_cancel(adap->transmitting, CEC_TX_STATUS_ABORTED);
+		adap->transmit_in_progress_aborted = true;
 
 	/* Cancel the pending timeout work. */
 	list_for_each_entry_safe(data, n, &adap->wait_queue, list) {
@@ -572,6 +572,7 @@ int cec_thread_func(void *_adap)
 		if (data->attempts == 0)
 			data->attempts = attempts;
 
+		adap->transmit_in_progress_aborted = false;
 		/* Tell the adapter to transmit, cancel on error */
 		if (adap->ops->adap_transmit(adap, data->attempts,
 					     signal_free_time, &data->msg))
@@ -599,6 +600,8 @@ void cec_transmit_done_ts(struct cec_adapter *adap, u8 status,
 	struct cec_msg *msg;
 	unsigned int attempts_made = arb_lost_cnt + nack_cnt +
 				     low_drive_cnt + error_cnt;
+	bool done = status & (CEC_TX_STATUS_MAX_RETRIES | CEC_TX_STATUS_OK);
+	bool aborted = adap->transmit_in_progress_aborted;
 
 	dprintk(2, "%s: status 0x%02x\n", __func__, status);
 	if (attempts_made < 1)
@@ -619,6 +622,7 @@ void cec_transmit_done_ts(struct cec_adapter *adap, u8 status,
 		goto wake_thread;
 	}
 	adap->transmit_in_progress = false;
+	adap->transmit_in_progress_aborted = false;
 
 	msg = &data->msg;
 
@@ -639,8 +643,7 @@ void cec_transmit_done_ts(struct cec_adapter *adap, u8 status,
 	 * the hardware didn't signal that it retried itself (by setting
 	 * CEC_TX_STATUS_MAX_RETRIES), then we will retry ourselves.
 	 */
-	if (data->attempts > attempts_made &&
-	    !(status & (CEC_TX_STATUS_MAX_RETRIES | CEC_TX_STATUS_OK))) {
+	if (!aborted && data->attempts > attempts_made && !done) {
 		/* Retry this message */
 		data->attempts -= attempts_made;
 		if (msg->timeout)
@@ -655,6 +658,8 @@ void cec_transmit_done_ts(struct cec_adapter *adap, u8 status,
 		goto wake_thread;
 	}
 
+	if (aborted && !done)
+		status |= CEC_TX_STATUS_ABORTED;
 	data->attempts = 0;
 
 	/* Always set CEC_TX_STATUS_MAX_RETRIES on error */
@@ -1596,6 +1601,9 @@ static void cec_activate_cnt_dec(struct cec_adapter *adap)
 	WARN_ON(adap->ops->adap_enable(adap, false));
 	adap->last_initiator = 0xff;
 	adap->transmit_in_progress = false;
+	adap->transmit_in_progress_aborted = false;
+	if (adap->transmitting)
+		cec_data_cancel(adap->transmitting, CEC_TX_STATUS_ABORTED);
 	mutex_unlock(&adap->devnode.lock);
 }
 

include/media/cec.h

@@ -163,6 +163,11 @@ struct cec_adap_ops {
  * @wait_queue:		queue of transmits waiting for a reply
  * @transmitting:	CEC messages currently being transmitted
  * @transmit_in_progress: true if a transmit is in progress
+ * @transmit_in_progress_aborted: true if a transmit is in progress is to be
+ *			aborted. This happens if the logical address is
+ *			invalidated while the transmit is ongoing. In that
+ *			case the transmit will finish, but will not retransmit
+ *			and be marked as ABORTED.
  * @kthread_config:	kthread used to configure a CEC adapter
  * @config_completion:	used to signal completion of the config kthread
  * @kthread:		main CEC processing thread
@@ -218,6 +223,7 @@ struct cec_adapter {
 	struct list_head wait_queue;
 	struct cec_data *transmitting;
 	bool transmit_in_progress;
+	bool transmit_in_progress_aborted;
 
 	struct task_struct *kthread_config;
 	struct completion config_completion;