[PATCH v5 2/2] serial: mxc: have putc use the TXFIFO

[Fabio Estevam]

On Wed, Nov 2, 2022 at 2:24 PM Pali Rohár <pali at kernel.org> wrote:

> Hello! This log just cleanly shows that UART TX FIFO is either broken or
> something drops its content prior all bytes are properly transmitted.
> Dropping HW TX FIFO is on most UARTs possible by resetting registers or
> reconfiguring buadrate.
>
> I have an idea, cannot some u-boot code calls some mxc function which
> changes parameters of UART and this will cause loosing of FIFO?
>
> For example I see two functions which are doing it. Could you try to add
> code which waits until content of FIFO is transmitted prior changing
> UART parameters?
>
> diff --git a/drivers/serial/serial_mxc.c b/drivers/serial/serial_mxc.c
> index 4cf79c1ca24f..9611d9bc8a00 100644
> --- a/drivers/serial/serial_mxc.c
> +++ b/drivers/serial/serial_mxc.c
> @@ -146,6 +146,9 @@ struct mxc_uart {
>
>  static void _mxc_serial_init(struct mxc_uart *base, int use_dte)
>  {
> +       while (!(readl(&base->ts) & UTS_TXEMPTY))
> +               ;
> +
>         writel(0, &base->cr1);
>         writel(0, &base->cr2);
>
> @@ -169,6 +172,9 @@ static void _mxc_serial_setbrg(struct mxc_uart *base, unsigned long clk,
>  {
>         u32 tmp;
>
> +       while (!(readl(&base->ts) & UTS_TXEMPTY))
> +               ;
> +

Tried your suggestion, but the print() content I added inside
board_init() is no longer printed.