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media: cec-gpio: select correct Signal Free Time

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If a receive is in progress or starts before the transmit has
a chance, then lower the Signal Free Time of the upcoming transmit
to no more than CEC_SIGNAL_FREE_TIME_NEW_INITIATOR.

This is per the specification requirements.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
This commit is contained in:
Hans Verkuil 2018-10-05 08:51:45 -04:00 committed by Mauro Carvalho Chehab
parent 7d867a1b76
commit c439d5c1e1
1 changed files with 20 additions and 0 deletions
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20
drivers/media/cec/cec-pin.c
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@ -935,6 +935,17 @@ static enum hrtimer_restart cec_pin_timer(struct hrtimer *timer)
/* Start bit, switch to receive state */
pin->ts = ts;
pin->state = CEC_ST_RX_START_BIT_LOW;
/*
* If a transmit is pending, then that transmit should
* use a signal free time of no more than
* CEC_SIGNAL_FREE_TIME_NEW_INITIATOR since it will
* have a new initiator due to the receive that is now
* starting.
*/
if (pin->tx_msg.len && pin->tx_signal_free_time >
CEC_SIGNAL_FREE_TIME_NEW_INITIATOR)
pin->tx_signal_free_time =
CEC_SIGNAL_FREE_TIME_NEW_INITIATOR;
break;
}
if (ktime_to_ns(pin->ts) == 0)
@ -1157,6 +1168,15 @@ static int cec_pin_adap_transmit(struct cec_adapter *adap, u8 attempts,
{
struct cec_pin *pin = adap->pin;
/*
* If a receive is in progress, then this transmit should use
* a signal free time of max CEC_SIGNAL_FREE_TIME_NEW_INITIATOR
* since when it starts transmitting it will have a new initiator.
*/
if (pin->state != CEC_ST_IDLE &&
signal_free_time > CEC_SIGNAL_FREE_TIME_NEW_INITIATOR)
signal_free_time = CEC_SIGNAL_FREE_TIME_NEW_INITIATOR;
pin->tx_signal_free_time = signal_free_time;
pin->tx_extra_bytes = 0;
pin->tx_msg = *msg;