[PATCH 4.19 125/220] media: cec-gpio: select correct Signal Free Time

Greg Kroah-Hartman
2019-11-22T11:03:47Z

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 0496d93b2b8fa..8f987bc0dd883 100644
--- 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;
--
2.20.1