[Qemu-devel] Re: [PATCH 2/2] pci: don't overwrite pci header type.

[Blue Swirl]

On Wed, Jun 16, 2010 at 6:51 PM, Michael S. Tsirkin <address@hidden> wrote:
> On Wed, Jun 16, 2010 at 06:41:22PM +0000, Blue Swirl wrote:
>> On Wed, Jun 16, 2010 at 8:54 AM, Michael S. Tsirkin <address@hidden> wrote:
>> > On Wed, Jun 16, 2010 at 11:20:02AM +0900, Isaku Yamahata wrote:
>> >> On Tue, Jun 15, 2010 at 12:12:07PM +0300, Michael S. Tsirkin wrote:
>> >> > On Tue, Jun 15, 2010 at 02:06:46PM +0900, Isaku Yamahata wrote:
>> >> > > Don't overwrite pci header type.
>> >> > > Otherwise, multi function bit which pci_init_header_type() sets
>> >> > > appropriately is lost.
>> >> > > Anyway PCI_HEADER_TYPE_NORMAL is zero, so it is unnecessary to zero
>> >> > > which is already zero cleared.
>> >> > >
>> >> > > Signed-off-by: Isaku Yamahata <address@hidden>
>> >> >
>> >> > ...
>> >> >
>> >> > > diff --git a/hw/apb_pci.c b/hw/apb_pci.c
>> >> > > index 31c8d70..cdf3bc2 100644
>> >> > > --- a/hw/apb_pci.c
>> >> > > +++ b/hw/apb_pci.c
>> >> > > @@ -428,7 +428,8 @@ static int pbm_pci_host_init(PCIDevice *d)
>> >> > >                   PCI_STATUS_DEVSEL_MEDIUM);
>> >> > >      pci_config_set_class(d->config, PCI_CLASS_BRIDGE_HOST);
>> >> > >      pci_set_byte(d->config + PCI_HEADER_TYPE,
>> >> > > -                 PCI_HEADER_TYPE_NORMAL);
>> >> > > +                 (pci_get_byte(d->config + PCI_HEADER_TYPE) &
>> >> > > +                  PCI_HEADER_TYPE_MULTI_FUNCTION) | 
>> >> > > PCI_HEADER_TYPE_NORMAL);
>> >> >
>> >> > what is this doing?
>> >>
>> >> It changes the header type to normal device(bit 1-7) without overwriting
>> >> multi function bit(bit 8).
>> >
>> > Don't we know what the multi function bit value is?
>> >
>> >> Apb host bridge specifies PCI_HEADER_TYPE_BRIDGE in PCIDeviceInfo,
>> >> on the other hand pbc_pci_host_init() sets the register
>> >> to PCI_HEADER_TYPE_NORMAL.
>> >> To be honest I don't know why it does so, but that is what Blue wants.
>> >
>> > BTW I think it would be prettier to have is_bridge instead of header_type
>> > as a qdev property. Agree?
>>
>> Good idea.
>>
>> >> So I touch only multi function bit(bit 8) and leave other bit (bit 1-7)
>> >> unchanged.
>> >>
>> >> If you don't like this hunk, I'll drop this hunk and leave it to Blue.
>> >> What do you think?
>> >
>> > Blue Swirl, could you comment on this please?
>>
>> I'd go for is_bridge and drop the override for header type in apb_pci.c then.
>
> Yes, but what header type does it need?

The type should be bridge (to allow writes to bridge registers), but
PCI header should use PCI_HEADER_TYPE_NORMAL (because the PBM
specification says so).

>> >> static PCIDeviceInfo pbm_pci_host_info = {
>> >>     .qdev.name = "pbm",
>> >>     .qdev.size = sizeof(PCIDevice),
>> >>     .init      = pbm_pci_host_init,
>> >>     .header_type  = PCI_HEADER_TYPE_BRIDGE,   <<<<< Here
>> >> };
>> >>
>> >> --
>> >> yamahata
>> >
>