media: tegra-cec: reset rx_buf_cnt when start bit detected

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@cisco.com>
Cc: <stable@vger.kernel.org>      # for v4.15 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

diff --git a/drivers/media/platform/tegra-cec/tegra_cec.c b/drivers/media/platform/tegra-cec/tegra_cec.c
index 92f93a8..aba488c 100644 (file)
--- 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;