Revert "serial: ns16550: fix debug uart putc called before init"

This reverts commit 6f57c34473d37b8da5e6a3764d0d377d748aeef1 since it
does not seem to work at least on rk3399.

The Rockchip Technical Reference Manual (TRM) for the rk3399 says the baud
rate prescaler register is readable only when USR[0] is zero. Since this
bit is defined as "reserved" in the socfpga cylcone5 TRM, let's rather
drop this than making the ns16550 debug uart more platform specific.

Reported-by: Roosen Henri <Henri.Roosen@ginzinger.com>
Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com

diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
index f21c240e64aa2d7802841f719e8ddbb017d2f7be..25b9d1724334e2b3d321760e235a0cd419ff588a 100644 (file)
--- a/drivers/serial/ns16550.c
+++ b/drivers/serial/ns16550.c
@@ -272,26 +272,12 @@ static inline void _debug_uart_init(void)
        serial_dout(&com_port->lcr, UART_LCRVAL);
 }
 
-static inline int NS16550_read_baud_divisor(struct NS16550 *com_port)
-{
-       int ret;
-
-       serial_dout(&com_port->lcr, UART_LCR_BKSE | UART_LCRVAL);
-       ret = serial_din(&com_port->dll) & 0xff;
-       ret |= (serial_din(&com_port->dlm) & 0xff) << 8;
-       serial_dout(&com_port->lcr, UART_LCRVAL);
-
-       return ret;
-}
-
 static inline void _debug_uart_putc(int ch)
 {
        struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE;
 
-       while (!(serial_din(&com_port->lsr) & UART_LSR_THRE)) {
-               if (!NS16550_read_baud_divisor(com_port))
-                       return;
-       }
+       while (!(serial_din(&com_port->lsr) & UART_LSR_THRE))
+               ;
        serial_dout(&com_port->thr, ch);
 }