[U-Boot] [PATCH] Revert "serial: ns16550: fix debug uart putc called before init"

[Kever Yang]

Hi Simon,


On 12/04/2018 04:55 AM, Simon Goldschmidt wrote:
> 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 at ginzinger.com>
> Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>

Reviewed-by:  Kever Yang <kever.yang at rock-chips.com>

Thanks,
- Kever
> ---
>
>  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);
>  }
>