Hi Casey,
On 7/8/2026 5:54 PM, Casey Connolly wrote:
Hi Balaji,
On 7/7/26 11:52, Balaji Selvanathan wrote:
Add IRQ status validation to distinguish legitimate UART data from
electrical noise in the RX FIFO.
When the UART cable is disconnected, the floating RX line can pick up
noise that the GENI hardware interprets as valid data and places in
the FIFO. So, check the RX IRQ status register for RX watermark or last
flags before reporting pending data.
Thanks for respinning this series. Is this patch still necessary with
the first one? Since we should no longer be in this state with noise
in the FIFO after resetting it correctly iiuc?
Even after fixing init sequence, still it stops at U-Boot CLI when the
UART cable is disconnected on QCS615-EVK, so seems SE_GENI_S_IRQ_STATUS
register has to be checked to make sure data is valid.
Thanks,
Balaji
Thanks,
// Casey
Signed-off-by: Balaji Selvanathan <[email protected]>
---
Changes in v2:
- No changes
---
drivers/serial/serial_msm_geni.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/drivers/serial/serial_msm_geni.c
b/drivers/serial/serial_msm_geni.c
index a580dee8c8a..07d38178759 100644
--- a/drivers/serial/serial_msm_geni.c
+++ b/drivers/serial/serial_msm_geni.c
@@ -483,15 +483,29 @@ 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);
+ u32 fifo_status;
+ u32 s_irq_status;
+ int word_count;
- if (input)
- return readl(priv->base + SE_GENI_RX_FIFO_STATUS) &
- RX_FIFO_WC_MSK;
- else
- return readl(priv->base + SE_GENI_TX_FIFO_STATUS) &
- TX_FIFO_WC_MSK;
+ if (input) {
+ fifo_status = readl(priv->base + SE_GENI_RX_FIFO_STATUS);
+ word_count = fifo_status & RX_FIFO_WC_MSK;
- return 0;
+ if (word_count > 0) {
+ /* Validate RX FIFO data with IRQ status */
+ 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)))
+ return 0;
+ }
+
+ return word_count;
+ } else {
+ fifo_status = readl(priv->base + SE_GENI_TX_FIFO_STATUS);
+ word_count = fifo_status & TX_FIFO_WC_MSK;
+
+ return word_count;
+ }
}
static const struct dm_serial_ops msm_serial_ops = {
