serial: sh-sci: Fix deadlock during RSCI FIFO overrun error

On RSCI IP, a deadlock occurs during a FIFO overrun error, as it uses a
different register to clear the FIFO overrun error status.

Cc: stable@kernel.org
Fixes: 0666e3f ("serial: sh-sci: Add support for RZ/T2H SCI")
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20251114101350.106699-3-biju.das.jz@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: bijudas

drivers/tty/serial/sh-sci.c

@@ -1198,8 +1198,16 @@ static int sci_handle_fifo_overrun(struct uart_port *port)
 
 	status = s->ops->read_reg(port, s->params->overrun_reg);
 	if (status & s->params->overrun_mask) {
-		status &= ~s->params->overrun_mask;
-		s->ops->write_reg(port, s->params->overrun_reg, status);
+		if (s->type == SCI_PORT_RSCI) {
+			/*
+			 * All of the CFCLR_*C clearing bits match the corresponding
+			 * CSR_*status bits. So, reuse the overrun mask for clearing.
+			 */
+			s->ops->clear_SCxSR(port, s->params->overrun_mask);
+		} else {
+			status &= ~s->params->overrun_mask;
+			s->ops->write_reg(port, s->params->overrun_reg, status);
+		}
 
 		port->icount.overrun++;