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

[Anthony Liguori]

On 06/16/2010 02:22 PM, Michael S. Tsirkin wrote:
> On Wed, Jun 16, 2010 at 07:02:54PM +0000, Blue Swirl wrote:
>    
> > 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).
> >      
> I can no longer get the PBM specs now: are there
> alternative links? Need to fix links in code.
>    

BTW, I set up http://wiki.qemu.org/Documentation/HardwareManuals so we 
could start archiving these specification when allowed.

Regards,

Anthony Liguori

>    
> > > > > > 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
> > > > > >              
> > > > >            
> > >        
>