[PATCH v7 03/12] serial: 8250: share the RX trigger conversion helper

[James Hilliard]

Drivers can supply receive-trigger thresholds through the RX trigger
callbacks without adding a legacy port type to uart_config[]. Extract the
threshold search into serial8250_bytes_to_fcr() so those drivers can use
the same conversion as the generic 8250 implementation.

Keep the implementation in 8250_port.c and share it within 8250_base.
Include the unsupported-table check and preserve the existing nearest-lower
selection and highest-encoding fallback.

Suggested-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen at linux.intel.com>
Signed-off-by: James Hilliard <james.hilliard1 at gmail.com>
---
 drivers/tty/serial/8250/8250.h      |  2 ++
 drivers/tty/serial/8250/8250_port.c | 14 ++++++++++----
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index 939b7d4209f1..8729619160ea 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -73,6 +73,8 @@ struct serial8250_config {
 	unsigned int	flags;
 };
 
+int serial8250_bytes_to_fcr(const u16 *rxtrig_bytes, u16 bytes);
+
 enum uart_port_type {
 	/* Internal 8250 only */
 	UART_PORT_AIROHA		= 124,
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 452851815ffc..73bc9e7ab703 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -3015,16 +3015,15 @@ static int fcr_get_rxtrig_bytes(struct uart_8250_port *up)
 	return bytes ? bytes : -EOPNOTSUPP;
 }
 
-static int bytes_to_fcr_rxtrig(struct uart_8250_port *up, u16 bytes)
+int serial8250_bytes_to_fcr(const u16 *rxtrig_bytes, u16 bytes)
 {
-	const struct serial8250_config *conf_type = &uart_config[up->port.type];
 	int i;
 
-	if (!conf_type->rxtrig_bytes[UART_FCR_R_TRIG_BITS(UART_FCR_R_TRIG_00)])
+	if (!rxtrig_bytes[UART_FCR_R_TRIG_BITS(UART_FCR_R_TRIG_00)])
 		return -EOPNOTSUPP;
 
 	for (i = 1; i < UART_FCR_R_TRIG_MAX_STATE; i++) {
-		if (bytes < conf_type->rxtrig_bytes[i])
+		if (bytes < rxtrig_bytes[i])
 			/* Use the nearest lower value */
 			return (--i) << UART_FCR_R_TRIG_SHIFT;
 	}
@@ -3032,6 +3031,13 @@ static int bytes_to_fcr_rxtrig(struct uart_8250_port *up, u16 bytes)
 	return UART_FCR_R_TRIG_11;
 }
 
+static int bytes_to_fcr_rxtrig(struct uart_8250_port *up, u16 bytes)
+{
+	const struct serial8250_config *conf_type = &uart_config[up->port.type];
+
+	return serial8250_bytes_to_fcr(conf_type->rxtrig_bytes, bytes);
+}
+
 static int do_get_rxtrig(struct tty_port *port)
 {
 	struct uart_state *state = container_of(port, struct uart_state, port);

-- 
2.53.0