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Commit b68d405a authored by Hans Verkuil's avatar Hans Verkuil Committed by Greg Kroah-Hartman
Browse files

media: cec: fix the Signal Free Time calculation 



commit 7d867a1b765e2b70815fec4964d7822a976ed349 upstream.

The calculation of the Signal Free Time in the framework was not
correct. If a message was received, then the next transmit should be
considered a New Initiator and use a shorter SFT value.

This was not done with the result that if both sides where continually
sending messages, they both could use the same SFT value and one side
could deny the other side access to the bus.

Note that this fix does not take the corner case into account where
a receive is in progress when you call adap_transmit.

Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Cc: <stable@vger.kernel.org>      # for v4.18 and up
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 94ec4487

drivers/media/cec/cec-adap.c

+7 −19
Original line number Original line Diff line number Diff line
@@ -513,9 +513,11 @@ int cec_thread_func(void *_adap) 
		if (data->attempts) {

		if (data->attempts) {

			/* should be >= 3 data bit periods for a retry */

			/* should be >= 3 data bit periods for a retry */

			signal_free_time = CEC_SIGNAL_FREE_TIME_RETRY;

			signal_free_time = CEC_SIGNAL_FREE_TIME_RETRY;

		} else if (data->new_initiator) {

		} else if (adap->last_initiator !=

			   cec_msg_initiator(&data->msg)) {

			/* should be >= 5 data bit periods for new initiator */

			/* should be >= 5 data bit periods for new initiator */

			signal_free_time = CEC_SIGNAL_FREE_TIME_NEW_INITIATOR;

			signal_free_time = CEC_SIGNAL_FREE_TIME_NEW_INITIATOR;

			adap->last_initiator = cec_msg_initiator(&data->msg);

		} else {

		} else {

			/*

			/*

			 * should be >= 7 data bit periods for sending another

			 * should be >= 7 data bit periods for sending another
@@ -700,7 +702,6 @@ int cec_transmit_msg_fh(struct cec_adapter *adap, struct cec_msg *msg, 
			struct cec_fh *fh, bool block)

			struct cec_fh *fh, bool block)

{

{

	struct cec_data *data;

	struct cec_data *data;

	u8 last_initiator = 0xff;





	msg->rx_ts = 0;

	msg->rx_ts = 0;

	msg->tx_ts = 0;

	msg->tx_ts = 0;
@@ -810,23 +811,6 @@ int cec_transmit_msg_fh(struct cec_adapter *adap, struct cec_msg *msg, 
	data->adap = adap;

	data->adap = adap;

	data->blocking = block;

	data->blocking = block;





	/*

	 * Determine if this message follows a message from the same

	 * initiator. Needed to determine the free signal time later on.

	 */

	if (msg->len > 1) {

		if (!(list_empty(&adap->transmit_queue))) {

			const struct cec_data *last;



			last = list_last_entry(&adap->transmit_queue,

					       const struct cec_data, list);

			last_initiator = cec_msg_initiator(&last->msg);

		} else if (adap->transmitting) {

			last_initiator =

				cec_msg_initiator(&adap->transmitting->msg);

		}

	}

	data->new_initiator = last_initiator != cec_msg_initiator(msg);

	init_completion(&data->c);

	init_completion(&data->c);

	INIT_DELAYED_WORK(&data->work, cec_wait_timeout);

	INIT_DELAYED_WORK(&data->work, cec_wait_timeout);
@@ -1014,6 +998,8 @@ void cec_received_msg_ts(struct cec_adapter *adap, 
	mutex_lock(&adap->lock);

	mutex_lock(&adap->lock);

	dprintk(2, "%s: %*ph\n", __func__, msg->len, msg->msg);

	dprintk(2, "%s: %*ph\n", __func__, msg->len, msg->msg);





	adap->last_initiator = 0xff;



	/* Check if this message was for us (directed or broadcast). */

	/* Check if this message was for us (directed or broadcast). */

	if (!cec_msg_is_broadcast(msg))

	if (!cec_msg_is_broadcast(msg))

		valid_la = cec_has_log_addr(adap, msg_dest);

		valid_la = cec_has_log_addr(adap, msg_dest);
@@ -1476,6 +1462,8 @@ void __cec_s_phys_addr(struct cec_adapter *adap, u16 phys_addr, bool block) 
	}

	}





	mutex_lock(&adap->devnode.lock);

	mutex_lock(&adap->devnode.lock);

	adap->last_initiator = 0xff;



	if ((adap->needs_hpd || list_empty(&adap->devnode.fhs)) &&

	if ((adap->needs_hpd || list_empty(&adap->devnode.fhs)) &&

	    adap->ops->adap_enable(adap, true)) {

	    adap->ops->adap_enable(adap, true)) {

		mutex_unlock(&adap->devnode.lock);

		mutex_unlock(&adap->devnode.lock);

include/media/cec.h

+1 −1
Original line number Original line Diff line number Diff line
@@ -63,7 +63,6 @@ struct cec_data { 
	struct delayed_work work;

	struct delayed_work work;

	struct completion c;

	struct completion c;

	u8 attempts;

	u8 attempts;

	bool new_initiator;

	bool blocking;

	bool blocking;

	bool completed;

	bool completed;

};

};
@@ -174,6 +173,7 @@ struct cec_adapter { 
	bool is_configuring;

	bool is_configuring;

	bool is_configured;

	bool is_configured;

	bool cec_pin_is_high;

	bool cec_pin_is_high;

	u8 last_initiator;

	u32 monitor_all_cnt;

	u32 monitor_all_cnt;

	u32 monitor_pin_cnt;

	u32 monitor_pin_cnt;

	u32 follower_cnt;

	u32 follower_cnt;