[PATCH] serial: 8250_omap: Implementation of Errata i2310 adding fifo level check

[Udit Kumar <u-kumar1@ti.com>]

As per Errata i2310[0], Erroneous timeout can be triggered,
if this Erroneous interrupt is not cleared then it may leads
to storm of interrupts.

This patch adding fifo empty check before applying errata.

[0] https://www.ti.com/lit/pdf/sprz536 page 23

Fixes: b67e830d38fa ("serial: 8250: 8250_omap: Fix possible interrupt storm on K3 SoCs")
Cc: stable@vger.kernel.org
Signed-off-by: Udit Kumar <u-kumar1@ti.com>
---
This is check is added on top of errata implementation v3 patch 
https://lore.kernel.org/all/20240619105903.165434-1-u-kumar1@ti.com/


 drivers/tty/serial/8250/8250_omap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index ddac0a13cf84..1af9aed99c65 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -672,7 +672,8 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
 	 * https://www.ti.com/lit/pdf/sprz536
 	 */
 	if (priv->habit & UART_RX_TIMEOUT_QUIRK &&
-		(iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT) {
+	    (iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT &&
+	    serial_port_in(port, UART_OMAP_RX_LVL) == 0) {
 		unsigned char efr2, timeout_h, timeout_l;
 
 		efr2 = serial_in(up, UART_OMAP_EFR2);
-- 
2.34.1