Allows tuning of the RX FIFO fill threshold and timeout. (The latter is
only applicable to SCIFA and SCIFB).

Signed-off-by: Ulrich Hecht <redacted>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/tty/serial/sh-sci.c | 87 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 4a165ed..f95a56c 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c

@@ -1055,6 +1055,66 @@ static void rx_fifo_timer_fn(unsigned long arg)
        scif_set_rtrg(port, 1);
 }

+static ssize_t rx_trigger_show(struct device *dev,
+                              struct device_attribute *attr,
+                              char *buf)
+{
+       struct uart_port *port = dev_get_drvdata(dev);
+       struct sci_port *sci = to_sci_port(port);
+
+       return sprintf(buf, "%d\n", sci->rx_trigger);
+}
+
+static ssize_t rx_trigger_store(struct device *dev,
+                               struct device_attribute *attr,
+                               const char *buf,
+                               size_t count)
+{
+       struct uart_port *port = dev_get_drvdata(dev);
+       struct sci_port *sci = to_sci_port(port);
+       long r;
+
+       if (kstrtol(buf, 0, &r) == -EINVAL)
+               return -EINVAL;
+       sci->rx_trigger = scif_set_rtrg(port, r);
+       scif_set_rtrg(port, 1);