On Fri Jul 10 11:53:18 2026 +0200, Hans Verkuil wrote:
> Keep track of Rx Low Drive conditions. Useful for detecting
> potential hardware/cable problems as it suggests unstable or
> incorrect voltage levels.
>
> Note that the Tx Low Drive conditions are already logged in
> the CEC core.
>
> Signed-off-by: Hans Verkuil <[email protected]>
> Reviewed-by: Mikko Perttunen <[email protected]>
> Signed-off-by: Mauro Carvalho Chehab <[email protected]>
Patch committed.
Thanks,
Mauro Carvalho Chehab
drivers/media/cec/platform/tegra/tegra_cec.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
---
diff --git a/drivers/media/cec/platform/tegra/tegra_cec.c
b/drivers/media/cec/platform/tegra/tegra_cec.c
index f8ffaeb78118..e22a4625f192 100644
--- a/drivers/media/cec/platform/tegra/tegra_cec.c
+++ b/drivers/media/cec/platform/tegra/tegra_cec.c
@@ -24,6 +24,7 @@
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
+#include <linux/seq_file.h>
#include <linux/clk/tegra.h>
#include <media/cec-notifier.h>
@@ -47,6 +48,7 @@ struct tegra_cec {
u32 tx_buf[CEC_MAX_MSG_SIZE];
u8 tx_buf_cur;
u8 tx_buf_cnt;
+ u32 rx_total_low_drives;
};
static inline u32 cec_read(struct tegra_cec *cec, u32 reg)
@@ -116,6 +118,13 @@ static irqreturn_t tegra_cec_irq_handler(int irq, void
*data)
return IRQ_WAKE_THREAD;
}
+ if (status & TEGRA_CEC_INT_STAT_RX_BUS_ERROR_DETECTED) {
+ dev_warn_ratelimited(dev, "RX bus error detected, generated low
drive\n");
+ cec->rx_total_low_drives++;
+ cec_write(cec, TEGRA_CEC_INT_STAT,
+ TEGRA_CEC_INT_STAT_RX_BUS_ERROR_DETECTED);
+ }
+
if ((status & TEGRA_CEC_INT_STAT_TX_ARBITRATION_FAILED) ||
(status & TEGRA_CEC_INT_STAT_TX_BUS_ANOMALY_DETECTED)) {
tegra_cec_error_recovery(cec);
@@ -241,6 +250,7 @@ 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_BUS_ERROR_DETECTED |
TEGRA_CEC_INT_MASK_RX_START_BIT_DETECTED);
/*
@@ -318,11 +328,20 @@ static int tegra_cec_adap_transmit(struct cec_adapter
*adap, u8 attempts,
return 0;
}
+static void tegra_cec_adap_status(struct cec_adapter *adap, struct seq_file
*file)
+{
+ struct tegra_cec *cec = adap->priv;
+
+ seq_printf(file, "receive low drive count: %u\n",
+ cec->rx_total_low_drives);
+}
+
static const struct cec_adap_ops tegra_cec_ops = {
.adap_enable = tegra_cec_adap_enable,
.adap_log_addr = tegra_cec_adap_log_addr,
.adap_transmit = tegra_cec_adap_transmit,
.adap_monitor_all_enable = tegra_cec_adap_monitor_all_enable,
+ .adap_status = tegra_cec_adap_status,
};
static int tegra_cec_probe(struct platform_device *pdev)
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