serial: core: Report magic multiplier extra baud rates

Report extra baud rates supported above the base rate for ports with the UPF_MAGIC_MULTIPLIER property, so that people have a way to find out that they can be used with their system, e.g.: Serial: 8250/16550 driver, 5 ports, IRQ sharing enabled printk: console [ttyS0] disabled serial8250.0: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A serial8250.0: ttyS0 extra baud rates supported: 230400, 460800 printk: console [ttyS0] enabled printk: bootconsole [uart8250] disabled serial8250.0: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A serial8250.0: ttyS1 extra baud rates supported: 230400, 460800 serial8250.0: ttyS2 at MMIO 0x1f000900 (irq = 20, base_baud = 230400) is a 16550A Otherwise there is no clear way to figure this out, as the feature is only reported as an obscure TTY flag in bit 16: $ cat /sys/class/tty/ttyS[0-2]/flags 0x10010040 0x10010040 0x90000040 $ Signed-off-by: Maciej W. Rozycki <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]>
pop-os · Jul 21, 2021 · e7b9193 · e7b9193
1 parent b1442c5
commit e7b9193
Showing 1 changed file with 8 additions and 0 deletions.
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
@@ -2314,6 +2314,14 @@ uart_report_port(struct uart_driver *drv, struct uart_port *port)
 	       port->dev ? ": " : "",
 	       port->name,
 	       address, port->irq, port->uartclk / 16, uart_type(port));
+
+	/* The magic multiplier feature is a bit obscure, so report it too.  */
+	if (port->flags & UPF_MAGIC_MULTIPLIER)
+		pr_info("%s%s%s extra baud rates supported: %d, %d",
+			port->dev ? dev_name(port->dev) : "",
+			port->dev ? ": " : "",
+			port->name,
+			port->uartclk / 8, port->uartclk / 4);
 }
 
 static void