[Qemu-devel] Re: [PATCH 7/7] pci bridge: implement secondary bus reset

[Isaku Yamahata]

On Thu, Nov 18, 2010 at 10:46:25AM +0200, Michael S. Tsirkin wrote:
> On Thu, Nov 18, 2010 at 04:29:10PM +0900, Isaku Yamahata wrote:
> > On Thu, Nov 18, 2010 at 09:05:30AM +0200, Michael S. Tsirkin wrote:
> > > On Wed, Nov 17, 2010 at 01:50:27PM +0900, Isaku Yamahata wrote:
> > > > Emulates secondary bus reset when secondary bus reset bit
> > > > is written from 0 to 1.
> > > > 
> > > > Signed-off-by: Isaku Yamahata <address@hidden>
> > > > Signed-off-by: Anthony Liguori <address@hidden>
> > > > ---
> > > >  hw/pci_bridge.c |   12 +++++++++++-
> > > >  1 files changed, 11 insertions(+), 1 deletions(-)
> > > > 
> > > > diff --git a/hw/pci_bridge.c b/hw/pci_bridge.c
> > > > index 58cc2e4..618a81e 100644
> > > > --- a/hw/pci_bridge.c
> > > > +++ b/hw/pci_bridge.c
> > > > @@ -139,6 +139,10 @@ pcibus_t pci_bridge_get_limit(const PCIDevice 
> > > > *bridge, uint8_t type)
> > > >  void pci_bridge_write_config(PCIDevice *d,
> > > >                               uint32_t address, uint32_t val, int len)
> > > >  {
> > > > +    PCIBridge *s = container_of(d, PCIBridge, dev);
> > > > +    uint16_t bridge_control = pci_get_word(d->config + 
> > > > PCI_BRIDGE_CONTROL);
> > > > +    uint16_t bridge_control_new;
> > > > +
> > > >      pci_default_write_config(d, address, val, len);
> > > >  
> > > >      if (/* io base/limit */
> > > > @@ -147,9 +151,15 @@ 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)) {
> > > > -        PCIBridge *s = container_of(d, PCIBridge, dev);
> > > >          pci_bridge_update_mappings(&s->sec_bus);
> > > >      }
> > > > +
> > > > +    bridge_control_new = pci_get_word(d->config + PCI_BRIDGE_CONTROL);
> > > > +    if (!(bridge_control & PCI_BRIDGE_CTL_BUS_RESET) &&
> > > > +        (bridge_control_new & PCI_BRIDGE_CTL_BUS_RESET)) {
> > > > +        /* 0 -> 1 */
> > > > +        pci_bus_reset(&s->sec_bus);
> > > > +    }
> > > >  }
> > > >  
> > > >  void pci_bridge_disable_base_limit(PCIDevice *dev)
> > > 
> > > Presumably this bit will have to be made writeable?
> > 
> > Yes, it's already writable.
> > static void pci_init_wmask_bridge(PCIDevice *d)
> > ...
> >    pci_set_word(d->wmask + PCI_BRIDGE_CONTROL, 0xffff);
> 
> Ouch, that's wrong, isn't it?
> Bits 15:12 are reserved, readonly, 0.
> 
> I think we need the following (untested).
> Comments?

Basically it looks good if you left bits 8-11 RO intentional.
qemu doesn't emulate pci bus cycles, so it won't matter.

Also, please include following hunk.

commit 8c76e0427234290a640499c1305cabd998d6f777
Author: Isaku Yamahata <address@hidden>
Date:   Fri Nov 19 17:08:57 2010 +0900

    pcie/port: initialize bridge control register properly
    
    pci generic layer initialized bridge control register
    according to pci spec. pcie deviates slightly from it,
    so initializes it properly.
    
    Signed-off-by: Isaku Yamahata <address@hidden>

diff --git a/hw/pcie_port.c b/hw/pcie_port.c
index 117de61..340dcdb 100644
--- a/hw/pcie_port.c
+++ b/hw/pcie_port.c
@@ -27,6 +27,14 @@ void pcie_port_init_reg(PCIDevice *d)
     pci_set_word(d->config + PCI_STATUS, 0);
     pci_set_word(d->config + PCI_SEC_STATUS, 0);
 
+    /* Unlike conventional pci bridge, some bits are hardwared to 0. */
+    pci_set_word(d->wmask + PCI_BRIDGE_CONTROL,
+                 PCI_BRIDGE_CTL_PARITY |
+                 PCI_BRIDGE_CTL_ISA |
+                 PCI_BRIDGE_CTL_VGA |
+                 PCI_BRIDGE_CTL_SERR |
+                 PCI_BRIDGE_CTL_BUS_RESET);
+
     /* 7.5.3.5 Prefetchable Memory Base Limit
      * The Prefetchable Memory Base and Prefetchable Memory Limit registers
      * must indicate that 64-bit addresses are supported, as defined in


> 
> pci: fix bridge control bit wmask
> 
> Bits 12 to 15 in bridge control register are reserver and must be
> read-only zero, curent mask is 0xffff which makes them writeable. Fix
> this up by using symbolic bit names for writeable bits instead of a
> hardcoded constant.
> 
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> 
> --
> 
> diff --git a/hw/pci.c b/hw/pci.c
> index 00ec8ea..7d6d5ad 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -588,7 +588,17 @@ static void pci_init_wmask_bridge(PCIDevice *d)
>      /* PCI_PREF_BASE_UPPER32 and PCI_PREF_LIMIT_UPPER32 */
>      memset(d->wmask + PCI_PREF_BASE_UPPER32, 0xff, 8);
>  
> -    pci_set_word(d->wmask + PCI_BRIDGE_CONTROL, 0xffff);
> +/* TODO: add this define to pci_regs.h in linux and then in qemu. */
> +#define  PCI_BRIDGE_CTL_VGA_16BIT 0x10       /* VGA 16-bit decode */
> +    pci_set_word(d->wmask + PCI_BRIDGE_CONTROL,
> +                 PCI_BRIDGE_CTL_PARITY |
> +                 PCI_BRIDGE_CTL_SERR |
> +                 PCI_BRIDGE_CTL_ISA |
> +                 PCI_BRIDGE_CTL_VGA |
> +                 PCI_BRIDGE_CTL_VGA_16BIT |
> +                 PCI_BRIDGE_CTL_MASTER_ABORT |
> +                 PCI_BRIDGE_CTL_BUS_RESET |
> +                 PCI_BRIDGE_CTL_FAST_BACK);
>  }
>  
>  static int pci_init_multifunction(PCIBus *bus, PCIDevice *dev)
> 

-- 
yamahata