[git:media_tree/fixes] media: tegra-cec: reset rx_buf_cnt when start bit detected

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Subject: media: tegra-cec: reset rx_buf_cnt when start bit detected
Author:  Hans Verkuil <hverkuil@xxxxxxxxx>
Date:    Wed Feb 28 05:47:07 2018 -0500

If a start bit is detected, then reset the receive buffer counter to 0.

This ensures that no stale data is in the buffer if a message is
broken off midstream due to e.g. a Low Drive condition and then
retransmitted.

The only Rx interrupts we need to listen to are RX_REGISTER_FULL (i.e.
a valid byte was received) and RX_START_BIT_DETECTED (i.e. a new
message starts and we need to reset the counter).

Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>      # for v4.15 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>

 drivers/media/platform/tegra-cec/tegra_cec.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

---

diff --git a/drivers/media/platform/tegra-cec/tegra_cec.c b/drivers/media/platform/tegra-cec/tegra_cec.c
index 92f93a880015..aba488cd0e64 100644
--- a/drivers/media/platform/tegra-cec/tegra_cec.c
+++ b/drivers/media/platform/tegra-cec/tegra_cec.c
@@ -172,16 +172,13 @@ static irqreturn_t tegra_cec_irq_handler(int irq, void *data)
 		}
 	}
 
-	if (status & (TEGRA_CEC_INT_STAT_RX_REGISTER_OVERRUN |
-		      TEGRA_CEC_INT_STAT_RX_BUS_ANOMALY_DETECTED |
-		      TEGRA_CEC_INT_STAT_RX_START_BIT_DETECTED |
-		      TEGRA_CEC_INT_STAT_RX_BUS_ERROR_DETECTED)) {
+	if (status & TEGRA_CEC_INT_STAT_RX_START_BIT_DETECTED) {
 		cec_write(cec, TEGRA_CEC_INT_STAT,
-			  (TEGRA_CEC_INT_STAT_RX_REGISTER_OVERRUN |
-			   TEGRA_CEC_INT_STAT_RX_BUS_ANOMALY_DETECTED |
-			   TEGRA_CEC_INT_STAT_RX_START_BIT_DETECTED |
-			   TEGRA_CEC_INT_STAT_RX_BUS_ERROR_DETECTED));
-	} else if (status & TEGRA_CEC_INT_STAT_RX_REGISTER_FULL) {
+			  TEGRA_CEC_INT_STAT_RX_START_BIT_DETECTED);
+		cec->rx_done = false;
+		cec->rx_buf_cnt = 0;
+	}
+	if (status & TEGRA_CEC_INT_STAT_RX_REGISTER_FULL) {
 		u32 v;
 
 		cec_write(cec, TEGRA_CEC_INT_STAT,
@@ -255,7 +252,7 @@ static int tegra_cec_adap_enable(struct cec_adapter *adap, bool enable)
 		  TEGRA_CEC_INT_MASK_TX_BUS_ANOMALY_DETECTED |
 		  TEGRA_CEC_INT_MASK_TX_FRAME_TRANSMITTED |
 		  TEGRA_CEC_INT_MASK_RX_REGISTER_FULL |
-		  TEGRA_CEC_INT_MASK_RX_REGISTER_OVERRUN);
+		  TEGRA_CEC_INT_MASK_RX_START_BIT_DETECTED);
 
 	cec_write(cec, TEGRA_CEC_HW_CONTROL, TEGRA_CEC_HWCTRL_TX_RX_MODE);
 	return 0;



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