media: cec-gpio: select correct Signal Free Time

[ 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>

diff --git a/drivers/media/cec/cec-pin.c b/drivers/media/cec/cec-pin.c
index 0496d93..8f987bc 100644 (file)
--- a/drivers/media/cec/cec-pin.c
+++ b/drivers/media/cec/cec-pin.c
@@ -936,6 +936,17 @@ 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)
@@ -1158,6 +1169,15 @@ 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;