[PATCH v4 11/13] serial: 8250: create lsr_save_mask

[Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>]

Allow drivers to alter LSR save mask.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
 drivers/tty/serial/8250/8250_core.c | 4 +++-
 drivers/tty/serial/8250/8250_port.c | 6 +++---
 include/linux/serial_8250.h         | 1 +
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index f67bc3b76f65..7cb1267559d4 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -278,7 +278,7 @@ static void serial8250_backup_timeout(struct timer_list *t)
 	 * ia64 and parisc boxes.
 	 */
 	lsr = serial_in(up, UART_LSR);
-	up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
+	up->lsr_saved_flags |= lsr & up->lsr_save_mask;
 	if ((iir & UART_IIR_NO_INT) && (up->ier & UART_IER_THRI) &&
 	    (!uart_circ_empty(&up->port.state->xmit) || up->port.x_char) &&
 	    (lsr & UART_LSR_THRE)) {
@@ -1097,6 +1097,8 @@ int serial8250_register_8250_port(const struct uart_8250_port *up)
 			ret = 0;
 		}
 
+		uart->lsr_save_mask = up->lsr_save_mask ?: LSR_SAVE_FLAGS;
+
 		/* Initialise interrupt backoff work if required */
 		if (up->overrun_backoff_time_ms > 0) {
 			uart->overrun_backoff_time_ms =
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index c2492b91b0cd..3be95e861f21 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1595,7 +1595,7 @@ static inline void __start_tx(struct uart_port *port)
 			unsigned int lsr;
 
 			lsr = serial_in(up, UART_LSR);
-			up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
+			up->lsr_saved_flags |= lsr & up->lsr_save_mask;
 			if (lsr & UART_LSR_THRE)
 				serial8250_tx_chars(up);
 		}
@@ -2029,7 +2029,7 @@ static unsigned int serial8250_tx_empty(struct uart_port *port)
 
 	spin_lock_irqsave(&port->lock, flags);
 	lsr = serial_port_in(port, UART_LSR);
-	up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
+	up->lsr_saved_flags |= lsr & up->lsr_save_mask;
 	spin_unlock_irqrestore(&port->lock, flags);
 
 	serial8250_rpm_put(up);
@@ -2110,7 +2110,7 @@ static void wait_for_xmitr(struct uart_8250_port *up, int bits)
 	for (;;) {
 		status = serial_in(up, UART_LSR);
 
-		up->lsr_saved_flags |= status & LSR_SAVE_FLAGS;
+		up->lsr_saved_flags |= status & up->lsr_save_mask;
 
 		if ((status & bits) == bits)
 			break;
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index 921df4c60062..aff76ea22287 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -120,6 +120,7 @@ struct uart_8250_port {
 	 */
 #define LSR_SAVE_FLAGS UART_LSR_BRK_ERROR_BITS
 	u16			lsr_saved_flags;
+	u16			lsr_save_mask;
 #define MSR_SAVE_FLAGS UART_MSR_ANY_DELTA
 	unsigned char		msr_saved_flags;
 
-- 
2.30.2