From 1a67969a99e4a89c31eb5fe7fa8d296e61310691 Mon Sep 17 00:00:00 2001
From: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Date: Mon, 3 Dec 2018 21:55:33 +0100
Subject: [PATCH] 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
---
 drivers/serial/ns16550.c | 18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
index f21c240e64..25b9d17243 100644
--- 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);
 }