Re: [PATCH qemu] [hw/char/bcm2835_aux] Fix receive FIFO filling up (raspi3)

[Peter Maydell]

[Added missing cc of qemu-devel]

On Mon, 22 Jul 2024 at 07:33, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>
> On 21/7/24 18:13, ~fvanhovell wrote:
> > From: Frederik van Hövell <frederik@fvhovell.nl>
> >
> > When a bare-metal application on the raspi3 board reads the
> > AUX_MU_STAT_REG MMIO register while the device's buffer is
> > at full receive FIFO capacity
> > (i.e. `s->read_count == BCM2835_AUX_RX_FIFO_LEN`) the
> > assertion `assert(s->read_count < BCM2835_AUX_RX_FIFO_LEN)`
> > fails.
> >
>
> Reported-by: Cryptjar <cryptjar@junk.studio>
> Suggested-by: Cryptjar <cryptjar@junk.studio>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>
> > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/459
> > Signed-off-by: Frederik van Hövell <frederik@fvhovell.nl>
> > ---
> >   hw/char/bcm2835_aux.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/hw/char/bcm2835_aux.c b/hw/char/bcm2835_aux.c
> > index 83990e20f7..fca2f27a55 100644
> > --- a/hw/char/bcm2835_aux.c
> > +++ b/hw/char/bcm2835_aux.c
> > @@ -138,7 +138,7 @@ static uint64_t bcm2835_aux_read(void *opaque, hwaddr 
> > offset, unsigned size)
> >           res = 0x30e; /* space in the output buffer, empty tx fifo, idle 
> > tx/rx */
> >           if (s->read_count > 0) {
> >               res |= 0x1; /* data in input buffer */
> > -            assert(s->read_count < BCM2835_AUX_RX_FIFO_LEN);
> > +            assert(s->read_count <= BCM2835_AUX_RX_FIFO_LEN);
> >               res |= ((uint32_t)s->read_count) << 16; /* rx fifo fill level 
> > */
> >           }
> >           return res;
>

thanks
-- PMM