Re: [Qemu-trivial] [PATCH] grlib_apbuart: always enable tx and rx

[Philippe Mathieu-Daudé]

Hi Frederic,

On 03/01/2018 07:02 AM, KONRAD Frederic wrote:
> We often use a bootloader for this board. So lets set the uart in a state
> which it can emit characters as if we were using a bootloader.
> 
> Signed-off-by: KONRAD Frederic <address@hidden>
> ---
>  hw/char/grlib_apbuart.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/char/grlib_apbuart.c b/hw/char/grlib_apbuart.c
> index bac11be..a8020ea 100644
> --- a/hw/char/grlib_apbuart.c
> +++ b/hw/char/grlib_apbuart.c
> @@ -265,8 +265,8 @@ static void grlib_apbuart_reset(DeviceState *d)
>  
>      /* Transmitter FIFO and shift registers are always empty in QEMU */
>      uart->status =  UART_TRANSMIT_FIFO_EMPTY | UART_TRANSMIT_SHIFT_EMPTY;
> -    /* Everything is off */
> -    uart->control = 0;
> +    /* Enable Tx and Rx as the bootloader would do */
> +    uart->control = UART_RECEIVE_ENABLE | UART_TRANSMIT_ENABLE;

I don't think this is the correct approach, as we want to reflect the
real hardware behavior here.

I think the correct QEMU-way is add a tiny asm bootloader in ram in
leon3_generic_hw_init(), which enables the UART.
See write_bootloader() in hw/mips/mips_fulong2e.c for example.

Regards,

Phil.

>      /* Flush receive FIFO */
>      uart->len = 0;
>      uart->current = 0;
>