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 <[email protected]>

Signed-off-by Simon Goldschmidt <[email protected]>

Quoted 12 lines · Simon Goldschmidt

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.

Quoted 2 lines

Reported-by Roosen Henri <[email protected]>

Signed-off-by Simon Goldschmidt <[email protected]>

Reviewed-by Philipp Tomsich <[email protected]>

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 <[email protected]>

Signed-off-by Simon Goldschmidt <[email protected]>

---

 drivers/serial/ns16550.c | 18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

drivers/serial/ns16550.c +2 -16

index f21c240e64..25b9d17243 100644
@@ -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);
 }
 

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 <[email protected]>

Signed-off-by Simon Goldschmidt <[email protected]>

Reviewed-by Philipp Tomsich <[email protected]>