Re: [PATCH] hw/misc: Add an iBT device model

[Titus Rwantare <titusr@google.com>]

On Fri, 24 Sept 2021 at 03:55, Cédric Le Goater <clg@kaod.org> wrote:
>
> Hello Titus,
>
> On 9/24/21 10:42, Philippe Mathieu-Daudé wrote:
> > On 9/24/21 01:48, Titus Rwantare wrote:
> >> Hello all,
> >>
> >> I'd like some clarification on how the following code transfers irqs
> >> back and forth:
> >>> b/hw/arm/aspeed_soc.c
> >>> +    /* iBT */
> >>> +    if (!sysbus_realize(SYS_BUS_DEVICE(&s->ibt), errp)) {
> >>> +        return;
> >>> +    }
> >>> +    memory_region_add_subregion(&s->lpc.iomem,
> >>> +                   sc->memmap[ASPEED_DEV_IBT] - sc->memmap[ASPEED_DEV_LPC],
> >>> +                   &s->ibt.iomem);
> >>> +    sysbus_connect_irq(SYS_BUS_DEVICE(&s->lpc), 1 + aspeed_lpc_ibt,
>
>
> The iBT device IRQ is connected to a subdevice irq of the LPC device.
> See aspeed_lpc_realize(). And triggered in aspeed_lpc_set_irq()

Yes, that side makes sense. I tried to get at that irq from
aspeed_ibt.c as follows:

qemu_irq_lower(ibt->lpc->subdevice_irqs[aspeed_lpc_ibt]); // or raise

static void aspeed_ibt_realize(DeviceState *dev, Error **errp)
{
AspeedIBTState *ibt = ASPEED_IBT(dev);
SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
IPMIInterface *ii = IPMI_INTERFACE(dev);
ibt->lpc = ASPEED_LPC(dev);
...

but this doesn't work and maybe I'm misusing the dynamic cast?

> >>> +                       qdev_get_gpio_in(DEVICE(&s->lpc), aspeed_lpc_ibt));
> >>> }
> >>
> >> and
> >>
> >>> hw/misc/aspeed_ibt.c
> >>> +static void aspeed_ibt_realize(DeviceState *dev, Error **errp)
> >>> +{
> >>> +    SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
> >>> +    AspeedIBTState *ibt = ASPEED_IBT(dev);
> >> ...
> >>> +
> >>> +    sysbus_init_irq(sbd, &ibt->irq);
> >>
> >> I ask because the code in aspeed_soc.c seems to connect to the
> >> lpc->subdevice_irqs[aspeed_lpc_ibt], initialised on
> >> hw/misc/aspeed_lpc.c:408.
> >> I noticed that bmc firmware running in qemu was checking the BT_CTRL
> >> register less frequently than I'd like while editing this patch to use
> >> the IPMIInterface.
>
> OK.
>
> This might be a problem in aspeed_ibt_update_irq(). This patch is
> an experiment from some few years ago. It still works good enough
> for the witherspoon-bmc and powernv9 machines for simple IPMI
> commands: fru, sdr, lan, power off (to be checked).
>
> Could you share your BMC and host command line ?
>

Host:
-chardev socket,id=ipmichr1,host=localhost,port=9999,reconnect=10 \
-device ipmi-bmc-extern,chardev=ipmichr1,id=bmc0 \
-device isa-ipmi-bt,bmc=bmc0,irq=10 -nodefaults

BMC:
-chardev socket,id=ipmichr1,host=localhost,port=9999,server=on,wait=off \
-device ipmi-host-extern,chardev=ipmichr1,responder=/machine/soc/ibt

But for this to work you need Hao's patch as well: [PATCH 7/8]
hw/ipmi: Add an IPMI external host device.