ns16550: do not override fifo size if explicitly set

If fifo size is already set via uart_params, do not force it to 16 - which
may not match the actual hardware. Specifically Exar cards have fifo of
256 bytes.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 16a73d0c0e4715f3ef8c7c27f111df248a900a75..97b85b0225ccf013f7f05537f28d38699c99df92 100644 (file)
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -357,7 +357,8 @@ static void __init ns16550_init_preirq(struct serial_port *port)
     ns16550_setup_preirq(uart);
 
     /* Check this really is a 16550+. Otherwise we have no FIFOs. */
-    if ( ((ns_read_reg(uart, UART_IIR) & 0xc0) == 0xc0) &&
+    if ( uart->fifo_size <= 1 &&
+         ((ns_read_reg(uart, UART_IIR) & 0xc0) == 0xc0) &&
          ((ns_read_reg(uart, UART_FCR) & UART_FCR_TRG14) == UART_FCR_TRG14) )
         uart->fifo_size = 16;
 }