Re: [PATCH] hw/char: disable ibex uart receive if the buffer is full

[Alistair Francis]

On Tue, Mar 9, 2021 at 2:27 AM Alexander Wagner
<alexander.wagner@ulal.de> wrote:
>
>
> On 08.03.21 14:47, Alistair Francis wrote:
> >>   hw/char/ibex_uart.c         | 20 +++++++++++++++-----
> >>   include/hw/char/ibex_uart.h |  4 ++++
> >>   2 files changed, 19 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/hw/char/ibex_uart.c b/hw/char/ibex_uart.c
> >> index 89f1182c9b..dac09d53d6 100644
> >> --- a/hw/char/ibex_uart.c
> >> +++ b/hw/char/ibex_uart.c
> >> @@ -66,7 +66,8 @@ static int ibex_uart_can_receive(void *opaque)
> >>   {
> >>       IbexUartState *s = opaque;
> >>
> >> -    if (s->uart_ctrl & R_CTRL_RX_ENABLE_MASK) {
> >> +    if ((s->uart_ctrl & R_CTRL_RX_ENABLE_MASK)
> >> +           && !(s->uart_status & R_STATUS_RXFULL_MASK)) {
> >>           return 1;
> >>       }
> >>
> >> @@ -83,6 +84,8 @@ static void ibex_uart_receive(void *opaque, const 
> >> uint8_t *buf, int size)
> >>
> >>       s->uart_status &= ~R_STATUS_RXIDLE_MASK;
> >>       s->uart_status &= ~R_STATUS_RXEMPTY_MASK;
> >> +    s->uart_status |= R_STATUS_RXFULL_MASK;
> > Doesn't this mean we set RXFULL on every receive? Shouldn't this check
> > the rx_level first?
> >
> > Alistair
>
> Thank you for having a look! :)
>
> Yes, this is correct. The RXFULL is currently set on every receive. The
> RXFULL is used to indicate to QEMU that the device cannot receive any
> further bytes.
>
> As the FIFO buffers are currently not yet implemented I thought it would
> make sense to behave like the OT UART could only receive one byte at a time.

Ah, good point.

Can you add a comment where it is set describing that then?

Alistair

>
> Alex
>