Re: [PATCH v2 2/3] hw/pci-host/raven: Manually reset the OR_IRQ device

[Peter Maydell]

On Sun, 2 May 2021 at 21:31, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> The OR_IRQ device is bus-less, thus isn't reset automatically.
> Add the raven_pcihost_reset() handler to manually reset the OR IRQ.
>
> Fixes: f40b83a4e31 ("40p: use OR gate to wire up raven PCI interrupts")
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  hw/pci-host/prep.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/hw/pci-host/prep.c b/hw/pci-host/prep.c
> index 0a9162fba97..7481bbf99d4 100644
> --- a/hw/pci-host/prep.c
> +++ b/hw/pci-host/prep.c
> @@ -230,6 +230,15 @@ static void raven_change_gpio(void *opaque, int n, int 
> level)
>      s->contiguous_map = level;
>  }
>
> +static void raven_pcihost_reset_enter(Object *obj, ResetType type)
> +{
> +    PREPPCIState *s = RAVEN_PCI_HOST_BRIDGE(obj);
> +
> +    if (!s->is_legacy_prep) {
> +        device_cold_reset(DEVICE(&s->or_irq));
> +    }
> +}
> +
>  static void raven_pcihost_realizefn(DeviceState *d, Error **errp)
>  {
>      SysBusDevice *dev = SYS_BUS_DEVICE(d);
> @@ -419,11 +428,13 @@ static Property raven_pcihost_properties[] = {
>  static void raven_pcihost_class_init(ObjectClass *klass, void *data)
>  {
>      DeviceClass *dc = DEVICE_CLASS(klass);
> +    ResettableClass *rc = RESETTABLE_CLASS(klass);
>
>      set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
>      dc->realize = raven_pcihost_realizefn;
>      device_class_set_props(dc, raven_pcihost_properties);
>      dc->fw_name = "pci";
> +    rc->phases.enter = raven_pcihost_reset_enter;
>  }

Why does this device have an OR gate rather than having its
map_irq function say "all PCI IRQs go to interrupt 0" ?
(The PCI core code provides you the "OR" functionality for
free, because it has to do that anyway for when multiple PCI
cards share a PCI IRQ -- see pci_change_irq_level() and
pci_bus_change_irq_level().

Supplementary question: why does the legacy_prep setup create 4
outbound sysbus IRQs when the map_irq function can only ever
return 0 or 1 ?

thanks
-- PMM