Re: [PATCH v5 07/11] hw/char: Initial commit of Ibex UART

[LIU Zhiwei]

Hi Alistair,

There are still some questions I don't understand.

1. Is the baud rate  or fifo a necessary feature to simulate?
As you can see, qemu_chr_fe_write will send the byte as soon as possible.
When you want to transmit a byte through WDATA,  you can call 
qemu_chr_fe_write directly.

2.  The baud rate calculation method is not strictly right.
I think when a byte write to FIFO,  char_tx_time * 8 is the correct time 
to send the byte instead of
char_tx_time * 4.

3.  Why add a watch here?
> +        s->uart_status |= UART_STATUS_TXEMPTY;
> +        s->uart_intr_state |= INTR_STATE_TX_EMPTY;
> +        s->uart_intr_state &= ~INTR_STATE_TX_WATERMARK;
> +        ibex_uart_update_irqs(s);
> +        return FALSE;
> +    }
> +
> +    ret = qemu_chr_fe_write(&s->chr, s->tx_fifo, s->tx_level);
> +
> +    if (ret >= 0) {
> +        s->tx_level -= ret;
> +        memmove(s->tx_fifo, s->tx_fifo + ret, s->tx_level);
> +    }
> +
> +    if (s->tx_level) {
> +        guint r = qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
> +                                        ibex_uart_xmit, s);
> +        if (!r) {
> +            s->tx_level = 0;
> +            return FALSE;
> +        }
> +    }
> + 

Zhiwei