[PATCH] serial: msm_geni: validate RX data with IRQ status

[Balaji Selvanathan]

The GENI UART hardware can retain stale data in the RX FIFO.
The msm_serial_pending() function was reporting this stale data as
pending input, causing U-Boot to incorrectly assume a key press and
stop at the CLI prompt instead of continuing the boot process.

Add IRQ status validation to distinguish between legitimate received
data and stale FIFO contents. Check the Secondary IRQ status register
for RX watermark or last flags before reporting pending data. If the
FIFO contains data but no valid IRQ flags are set, ignore it as stale.

Signed-off-by: Balaji Selvanathan <balaji.selvanathan at oss.qualcomm.com>
---
 drivers/serial/serial_msm_geni.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/serial/serial_msm_geni.c b/drivers/serial/serial_msm_geni.c
index 3dca581f68f..6d30f150966 100644
--- a/drivers/serial/serial_msm_geni.c
+++ b/drivers/serial/serial_msm_geni.c
@@ -424,13 +424,30 @@ static int msm_serial_getc(struct udevice *dev)
 static int msm_serial_pending(struct udevice *dev, bool input)
 {
 	struct msm_serial_data *priv = dev_get_priv(dev);
-
-	if (input)
-		return readl(priv->base + SE_GENI_RX_FIFO_STATUS) &
-			   RX_FIFO_WC_MSK;
-	else
+	u32 rx_fifo_status, s_irq_status;
+	int result;
+
+	if (input) {
+		rx_fifo_status = readl(priv->base + SE_GENI_RX_FIFO_STATUS);
+		result = rx_fifo_status & RX_FIFO_WC_MSK;
+
+		/*
+		 * Validate RX data with IRQ status
+		 * Only report pending data if valid RX IRQ indicators are set.
+		 */
+		if (result) {
+			s_irq_status = readl(priv->base + SE_GENI_S_IRQ_STATUS);
+
+			if (!(s_irq_status & (S_RX_FIFO_WATERMARK_EN | S_RX_FIFO_LAST_EN))) {
+				/* No valid RX IRQ, ignore stale data */
+				return 0;
+			}
+		}
+		return result;
+	} else {
 		return readl(priv->base + SE_GENI_TX_FIFO_STATUS) &
 			   TX_FIFO_WC_MSK;
+	}
 
 	return 0;
 }

---
base-commit: 6902fb4c17faa375003124c451c2550deab5463d
change-id: 20260629-uart-e07d893e4508

Best regards,
-- 
Balaji Selvanathan <balaji.selvanathan at oss.qualcomm.com>