Re: [PATCH v3 1/6] vt82c686: Implement control of serial port io ranges via config regs

[BALATON Zoltan]

On Tue, 23 Feb 2021, David Gibson wrote:
> On Mon, Feb 22, 2021 at 04:22:06PM +0100, BALATON Zoltan wrote:
> > In VIA super south bridge the io ranges of superio components
> > (parallel and serial ports and FDC) can be controlled by superio
> > config registers to set their base address and enable/disable them.
> > This is not easy to implement in QEMU because ISA emulation is only
> > designed to set io base address once on creating the device and io
> > ranges are registered at creation and cannot easily be disabled or
> > moved later.
> >
> > In this patch we hack around that but only for serial ports because
> > those have a single io range at port base that's relatively easy to
> > handle and it's what guests actually use and set address different
> > than the default.
> >
> > We do not attempt to handle controlling the parallel and FDC regions
> > because those have multiple io ranges so handling them would be messy
> > and guests either don't change their deafult or don't care. We could
> > even get away with disabling and not emulating them, but since they
> > are already there, this patch leaves them mapped at their default
> > address just in case this could be useful for a guest in the future.
> >
> > Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
>
> The maintainers of the hw/isa/vt82c686.c should probably be CCed on this.

He is (but may not be obvious because the accent in Phil's name is not 
handled well by my mail host so to avoid misspelling his name I've just 
omitted it). And he also said these should go in via some other tree:

https://lists.nongnu.org/archive/html/qemu-devel/2021-02/msg06551.html

He may still review or ack these but I guess he'd need some time.

I'll do the other changes you suggested.

Regards,
BALATON Zoltan

> > ---
> >  hw/isa/vt82c686.c | 84 +++++++++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 82 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
> > index 5db9b1706c..98bd57a074 100644
> > --- a/hw/isa/vt82c686.c
> > +++ b/hw/isa/vt82c686.c
> > @@ -252,8 +252,24 @@ static const TypeInfo vt8231_pm_info = {
> >  typedef struct SuperIOConfig {
> >      uint8_t regs[0x100];
> >      MemoryRegion io;
> > +    ISASuperIODevice *superio;
> > +    MemoryRegion *serial_io[SUPERIO_MAX_SERIAL_PORTS];
> >  } SuperIOConfig;
> >
> > +static MemoryRegion *find_subregion(ISADevice *d, MemoryRegion *parent,
> > +                                    int offs)
> > +{
> > +    MemoryRegion *subregion, *mr = NULL;
> > +
> > +    QTAILQ_FOREACH(subregion, &parent->subregions, subregions_link) {
> > +        if (subregion->addr == offs) {
> > +            mr = subregion;
> > +            break;
> > +        }
> > +    }
> > +    return mr;
> > +}
> > +
> >  static void superio_cfg_write(void *opaque, hwaddr addr, uint64_t data,
> >                                unsigned size)
> >  {
> > @@ -279,7 +295,53 @@ static void superio_cfg_write(void *opaque, hwaddr addr, 
> > uint64_t data,
> >      case 0xfd ... 0xff:
> >          /* ignore write to read only registers */
> >          return;
> > -    /* case 0xe6 ... 0xe8: Should set base port of parallel and serial */
> > +    case 0xe2:
> > +    {
> > +        data &= 0x1f;
> > +        if (data & BIT(2)) { /* Serial port 1 enable */
> > +            ISADevice *dev = sc->superio->serial[0];
> > +            if (!memory_region_is_mapped(sc->serial_io[0])) {
> > +                memory_region_add_subregion(isa_address_space_io(dev),
> > +                                            dev->ioport_id, sc->serial_io[0]);
> > +            }
> > +        } else {
> > +            MemoryRegion *io = isa_address_space_io(sc->superio->serial[0]);
> > +            if (memory_region_is_mapped(sc->serial_io[0])) {
> > +                memory_region_del_subregion(io, sc->serial_io[0]);
> > +            }
> > +        }
> > +        if (data & BIT(3)) { /* Serial port 2 enable */
> > +            ISADevice *dev = sc->superio->serial[1];
> > +            if (!memory_region_is_mapped(sc->serial_io[1])) {
> > +                memory_region_add_subregion(isa_address_space_io(dev),
> > +                                            dev->ioport_id, sc->serial_io[1]);
> > +            }
> > +        } else {
> > +            MemoryRegion *io = isa_address_space_io(sc->superio->serial[1]);
> > +            if (memory_region_is_mapped(sc->serial_io[1])) {
> > +                memory_region_del_subregion(io, sc->serial_io[1]);
> > +            }
> > +        }
> > +        break;
> > +    }
> > +    case 0xe7: /* Serial port 1 io base address */
> > +    {
> > +        data &= 0xfe;
> > +        sc->superio->serial[0]->ioport_id = data << 2;
> > +        if (memory_region_is_mapped(sc->serial_io[0])) {
> > +            memory_region_set_address(sc->serial_io[0], data << 2);
> > +        }
> > +        break;
> > +    }
> > +    case 0xe8: /* Serial port 2 io base address */
> > +    {
> > +        data &= 0xfe;
> > +        sc->superio->serial[1]->ioport_id = data << 2;
> > +        if (memory_region_is_mapped(sc->serial_io[1])) {
> > +            memory_region_set_address(sc->serial_io[1], data << 2);
> > +        }
> > +        break;
> > +    }
> >      default:
> >          qemu_log_mask(LOG_UNIMP,
> >                        "via_superio_cfg: unimplemented register 0x%x\n", idx);
> > @@ -385,6 +447,7 @@ static void vt82c686b_realize(PCIDevice *d, Error **errp)
> >      DeviceState *dev = DEVICE(d);
> >      ISABus *isa_bus;
> >      qemu_irq *isa_irq;
> > +    ISASuperIOClass *ic;
> >      int i;
> >
> >      qdev_init_gpio_out(dev, &s->cpu_intr, 1);
> > @@ -394,7 +457,9 @@ static void vt82c686b_realize(PCIDevice *d, Error **errp)
> >      isa_bus_irqs(isa_bus, i8259_init(isa_bus, *isa_irq));
> >      i8254_pit_init(isa_bus, 0x40, 0, NULL);
> >      i8257_dma_init(isa_bus, 0);
> > -    isa_create_simple(isa_bus, TYPE_VT82C686B_SUPERIO);
> > +    s->superio_cfg.superio = ISA_SUPERIO(isa_create_simple(isa_bus,
> > +                                                      TYPE_VT82C686B_SUPERIO));
> > +    ic = ISA_SUPERIO_GET_CLASS(s->superio_cfg.superio);
> >      mc146818_rtc_init(isa_bus, 2000, NULL);
> >
> >      for (i = 0; i < PCI_CONFIG_HEADER_SIZE; i++) {
> > @@ -412,6 +477,21 @@ static void vt82c686b_realize(PCIDevice *d, Error **errp)
> >       */
> >      memory_region_add_subregion(isa_bus->address_space_io, 0x3f0,
> >                                  &s->superio_cfg.io);
> > +
> > +    /* Grab io regions of serial devices so we can control them */
> > +    for (i = 0; i < ic->serial.count; i++) {
> > +        ISADevice *sd = s->superio_cfg.superio->serial[i];
> > +        MemoryRegion *io = isa_address_space_io(sd);
> > +        MemoryRegion *mr = find_subregion(sd, io, sd->ioport_id);
> > +        if (!mr) {
> > +            error_setg(errp, "Could not get io region for serial %d", i);
> > +            return;
> > +        }
> > +        s->superio_cfg.serial_io[i] = mr;
> > +        if (memory_region_is_mapped(mr)) {
> > +            memory_region_del_subregion(io, mr);
> > +        }
> > +    }
> >  }
> >
> >  static void via_class_init(ObjectClass *klass, void *data)