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Re: [Qemu-devel] [PATCH] pci: Teach PCI Bridges about VGA routing


From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] [PATCH] pci: Teach PCI Bridges about VGA routing
Date: Thu, 28 Feb 2013 23:48:23 +0200

On Thu, Feb 28, 2013 at 01:34:39PM -0700, Alex Williamson wrote:
> On Thu, 2013-02-28 at 22:26 +0200, Michael S. Tsirkin wrote:
> > On Thu, Feb 28, 2013 at 12:00:03PM -0700, Alex Williamson wrote:
> > > Each PCI Bridge has a set of implied VGA regions that are enabled
> > > when the VGA bit is set in the bridge control register.  This allows
> > > VGA devices behind bridges.
> > > 
> > > Signed-off-by: Alex Williamson <address@hidden>
> > > ---
> > >  hw/pci/pci_bridge.c |   47 
> > > ++++++++++++++++++++++++++++++++++++++++++++---
> > >  hw/pci/pci_bus.h    |   15 +++++++++++++++
> > >  2 files changed, 59 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c
> > > index 995842a..42cbfd1 100644
> > > --- a/hw/pci/pci_bridge.c
> > > +++ b/hw/pci/pci_bridge.c
> > > @@ -151,6 +151,37 @@ static void pci_bridge_init_alias(PCIBridge *bridge, 
> > > MemoryRegion *alias,
> > >      memory_region_add_subregion_overlap(parent_space, base, alias, 1);
> > >  }
> > >  
> > > +static void pci_bridge_init_vga_aliases(PCIBridge *br, PCIBus *parent,
> > > +                                        PCIBridgeVgaWindows *vga)
> > > +{
> > > +    uint16_t cmd = pci_get_word(br->dev.config + PCI_COMMAND);
> > > +    uint8_t brctl = pci_get_byte(br->dev.config + PCI_BRIDGE_CONTROL);
> > > +
> > > +    memory_region_init_alias(&vga->alias_io_lo, "pci_bridge_vga_io_lo",
> > > +                             &br->address_space_io, 0x3b0, 0xc);
> > > +    memory_region_add_subregion_overlap(parent->address_space_io, 0x3b0,
> > > +                                        &vga->alias_io_lo, 1);
> > > +
> > > +    memory_region_init_alias(&vga->alias_io_hi, "pci_bridge_vga_io_hi",
> > > +                             &br->address_space_io, 0x3c0, 0x20);
> > > +    memory_region_add_subregion_overlap(parent->address_space_io, 0x3c0,
> > > +                                        &vga->alias_io_hi, 1);
> > > +
> > > +    if (!(cmd & PCI_COMMAND_IO) || !(brctl & PCI_BRIDGE_CTL_VGA)) {
> > > +        memory_region_set_enabled(&vga->alias_io_lo, false);
> > > +        memory_region_set_enabled(&vga->alias_io_hi, false);
> > > +    }
> > > +
> > > +    memory_region_init_alias(&vga->alias_mem, "pci_bridge_vga_mem",
> > > +                             &br->address_space_mem, 0xa0000, 0x20000);
> > > +    memory_region_add_subregion_overlap(parent->address_space_mem, 
> > > 0xa0000,
> > > +                                        &vga->alias_mem, 1);
> > > +
> > > +    if (!(cmd & PCI_COMMAND_MEMORY) || !(brctl & PCI_BRIDGE_CTL_VGA)) {
> > > +        memory_region_set_enabled(&vga->alias_mem, false);
> > > +    }
> > > +}
> > > +
> > >  static PCIBridgeWindows *pci_bridge_region_init(PCIBridge *br)
> > >  {
> > >      PCIBus *parent = br->dev.bus;
> > > @@ -175,7 +206,8 @@ static PCIBridgeWindows 
> > > *pci_bridge_region_init(PCIBridge *br)
> > >                            &br->address_space_io,
> > >                            parent->address_space_io,
> > >                            cmd & PCI_COMMAND_IO);
> > > -   /* TODO: optinal VGA and VGA palette snooping support. */
> > > +
> > > +    pci_bridge_init_vga_aliases(br, parent, &w->vga);
> > >  
> > >      return w;
> > >  }
> > > @@ -187,6 +219,9 @@ static void pci_bridge_region_del(PCIBridge *br, 
> > > PCIBridgeWindows *w)
> > >      memory_region_del_subregion(parent->address_space_io, &w->alias_io);
> > >      memory_region_del_subregion(parent->address_space_mem, 
> > > &w->alias_mem);
> > >      memory_region_del_subregion(parent->address_space_mem, 
> > > &w->alias_pref_mem);
> > > +    memory_region_del_subregion(parent->address_space_io, 
> > > &w->vga.alias_io_lo);
> > > +    memory_region_del_subregion(parent->address_space_io, 
> > > &w->vga.alias_io_hi);
> > > +    memory_region_del_subregion(parent->address_space_mem, 
> > > &w->vga.alias_mem);
> > >  }
> > >  
> > >  static void pci_bridge_region_cleanup(PCIBridge *br, PCIBridgeWindows *w)
> > > @@ -194,6 +229,9 @@ static void pci_bridge_region_cleanup(PCIBridge *br, 
> > > PCIBridgeWindows *w)
> > >      memory_region_destroy(&w->alias_io);
> > >      memory_region_destroy(&w->alias_mem);
> > >      memory_region_destroy(&w->alias_pref_mem);
> > > +    memory_region_destroy(&w->vga.alias_io_lo);
> > > +    memory_region_destroy(&w->vga.alias_io_hi);
> > > +    memory_region_destroy(&w->vga.alias_mem);
> > >      g_free(w);
> > >  }
> > >  
> > > @@ -227,7 +265,10 @@ void pci_bridge_write_config(PCIDevice *d,
> > >  
> > >          /* memory base/limit, prefetchable base/limit and
> > >             io base/limit upper 16 */
> > > -        ranges_overlap(address, len, PCI_MEMORY_BASE, 20)) {
> > > +        ranges_overlap(address, len, PCI_MEMORY_BASE, 20) ||
> > > +
> > > +        /* vga enable */
> > > +        ranges_overlap(address, len, PCI_BRIDGE_CONTROL, 1)) {
> > >          pci_bridge_update_mappings(s);
> > >      }
> > >  
> > > @@ -294,7 +335,7 @@ void pci_bridge_reset(DeviceState *qdev)
> > >      pci_set_long(conf + PCI_PREF_BASE_UPPER32, 0);
> > >      pci_set_long(conf + PCI_PREF_LIMIT_UPPER32, 0);
> > >  
> > > -    pci_set_word(conf + PCI_BRIDGE_CONTROL, 0);
> > > +    pci_set_byte(conf + PCI_BRIDGE_CONTROL, 0);
> > 
> > Hang on, you are leaving PCI_BRIDGE_CTL_VGA read-only?
> > Shouldn't it be writeable?
> 
> It's writable for me, I've got SeaBIOS enabling it.  Both
> pci_init_mask_bridge and pcie_port_init_reg are marking it writable in
> wmask.
> 
> > And then I'd say disable everything on reset and then
> > re-enable for the default bridge.
> 
> The above chunk here is the disable on reset, we were just incorrectly
> setting a word instead of a byte.

Just re-checked the spec, bridge-control register is a 16 bit one.
In any case I'd like such unrelated fixes be noted in the commit log
please.

> I just sent a patch to SeaBIOS that
> will enable a path to the first VGA device if the platform doesn't
> already provide it with one.  Thanks,
> 
> Alex
> 
> > >  }
> > >  
> > >  /* default qdev initialization function for PCI-to-PCI bridge */
> > > diff --git a/hw/pci/pci_bus.h b/hw/pci/pci_bus.h
> > > index f905b9e..60d5378 100644
> > > --- a/hw/pci/pci_bus.h
> > > +++ b/hw/pci/pci_bus.h
> > > @@ -36,6 +36,20 @@ struct PCIBus {
> > >      int *irq_count;
> > >  };
> > >  
> > > +typedef struct PCIBridgeVgaWindows PCIBridgeVgaWindows;
> > > +
> > > +/*
> > > + * When bridge control VGA forwarding is enabled, bridges will provide
> > > + * positive decode on the PCI VGA defined I/O port and MMIO ranges noted
> > > + * below.  When set, forwarding is only qualified on the I/O and memory
> > > + * enable bits in the bridge command register.
> > > + */
> > > +struct PCIBridgeVgaWindows {
> > > +    MemoryRegion alias_io_lo; /* I/O ports 0x3b0 - 0x3bb */
> > > +    MemoryRegion alias_io_hi; /* I/O ports 0x3c0 - 0x3df */
> > > +    MemoryRegion alias_mem; /* MMIO 0xa0000 - 0xbffff */
> > > +};
> > > +
> > >  typedef struct PCIBridgeWindows PCIBridgeWindows;
> > >  
> > >  /*
> > > @@ -47,6 +61,7 @@ struct PCIBridgeWindows {
> > >      MemoryRegion alias_pref_mem;
> > >      MemoryRegion alias_mem;
> > >      MemoryRegion alias_io;
> > > +    PCIBridgeVgaWindows vga;
> > >  };
> > >  
> > >  struct PCIBridge {
> 
> 



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