Re: [Qemu-devel] [PATCH 2/3] pc: port 92 reset requires a low->high transition

[Anthony Liguori <aliguori@us.ibm.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> The PIIX datasheet says that "before another INIT pulse can be
> generated via [port 92h], [bit 0] must be written back to a
> zero.
>
> This bug is masked right now because a full reset will clear the
> value of port 92h.  But once we implement soft reset correctly,
> the next attempt to enable the A20 line by setting bit 1 (and
> leaving the others untouched) will cause another reset.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>

Regards,

Anthony Liguori

> ---
>  hw/pc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/pc.c b/hw/pc.c
> index 07caba7..523db1f 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -435,11 +435,12 @@ static void port92_write(void *opaque, hwaddr addr, uint64_t val,
>                           unsigned size)
>  {
>      Port92State *s = opaque;
> +    int oldval = s->outport;
>  
>      DPRINTF("port92: write 0x%02x\n", val);
>      s->outport = val;
>      qemu_set_irq(*s->a20_out, (val >> 1) & 1);
> -    if (val & 1) {
> +    if ((val & 1) && !(oldval & 1)) {
>          qemu_system_reset_request();
>      }
>  }
> -- 
> 1.8.1.4