serial: Test/disable MSIs if switching from N_PPS

Switching to the N_PPS line discipline may require enabling
modem status interrupts; conversely switching from N_PPS may
require disabling modem status interrupts.

Affected drivers:
8250
amba-pl010
atmel

Cc: Nicolas Ferre <[e-mail]>
Cc: Russell King <[e-mail]>
Signed-off-by: Peter Hurley <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/8250/8250_core.c

···
 	serial8250_rpm_put(up);
 }
 
+static void serial8250_disable_ms(struct uart_port *port)
+{
+	struct uart_8250_port *up =
+		container_of(port, struct uart_8250_port, port);
+
+	/* no MSR capabilities */
+	if (up->bugs & UART_BUG_NOMSR)
+		return;
+
+	up->ier &= ~UART_IER_MSI;
+	serial_port_out(port, UART_IER, up->ier);
+}
+
 static void serial8250_enable_ms(struct uart_port *port)
 {
 	struct uart_8250_port *up = up_to_u8250p(port);
···
 		spin_lock_irq(&port->lock);
 		serial8250_enable_ms(port);
 		spin_unlock_irq(&port->lock);
-	} else
+	} else {
 		port->flags &= ~UPF_HARDPPS_CD;
+		if (!UART_ENABLE_MS(port, termios->c_cflag)) {
+			spin_lock_irq(&port->lock);
+			serial8250_disable_ms(port);
+			spin_unlock_irq(&port->lock);
+		}
+	}
 }
 
 

drivers/tty/serial/amba-pl010.c

···
 	writel(cr, uap->port.membase + UART010_CR);
 }
 
+static void pl010_disable_ms(struct uart_port *port)
+{
+	struct uart_amba_port *uap = (struct uart_amba_port *)port;
+	unsigned int cr;
+
+	cr = readb(uap->port.membase + UART010_CR);
+	cr &= ~UART010_CR_MSIE;
+	writel(cr, uap->port.membase + UART010_CR);
+}
+
 static void pl010_enable_ms(struct uart_port *port)
 {
 	struct uart_amba_port *uap =
···
 		spin_lock_irq(&port->lock);
 		pl010_enable_ms(port);
 		spin_unlock_irq(&port->lock);
-	} else
+	} else {
 		port->flags &= ~UPF_HARDPPS_CD;
+		if (!UART_ENABLE_MS(port, termios->c_cflag)) {
+			spin_lock_irq(&port->lock);
+			pl010_disable_ms(port);
+			spin_unlock_irq(&port->lock);
+		}
+	}
 }
 
 static const char *pl010_type(struct uart_port *port)

drivers/tty/serial/atmel_serial.c

···
 		spin_unlock_irq(&port->lock);
 	} else {
 		port->flags &= ~UPF_HARDPPS_CD;
+		if (!UART_ENABLE_MS(port, termios->c_cflag)) {
+			spin_lock_irq(&port->lock);
+			atmel_disable_ms(port);
+			spin_unlock_irq(&port->lock);
+		}
 	}
 }