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    Subject[PATCH AUTOSEL 4.14 068/115] media: cec-gpio: select correct Signal Free Time
    Date
    From: Hans Verkuil <hans.verkuil@cisco.com>

    [ Upstream commit c439d5c1e13dbf66cff53455432f21d4d0536c51 ]

    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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/media/cec/cec-pin.c | 20 ++++++++++++++++++++
    1 file changed, 20 insertions(+)

    diff --git a/drivers/media/cec/cec-pin.c b/drivers/media/cec/cec-pin.c
    index c003b8eac6176..68fc6a24d0771 100644
    --- a/drivers/media/cec/cec-pin.c
    +++ b/drivers/media/cec/cec-pin.c
    @@ -529,6 +529,17 @@ 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 (pin->ts == 0)
    @@ -690,6 +701,15 @@ 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_msg = *msg;
    pin->work_tx_status = 0;
    --
    2.20.1
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