[Qemu-devel] Re: [PATCH v2 6/6] pci bridge: implement secondary bus reset

[Michael S. Tsirkin]

On Fri, Nov 19, 2010 at 06:56:03PM +0900, Isaku Yamahata wrote:
> Emulates secondary bus reset when secondary bus reset bit
> is written from 0 to 1.
> 

Interesting. This is not exactly what happens on real hardware
though: there, RST# stays asserted until bit is cleared.
So for example attempts to scan the secondary bus will
return nothing.
Can implement this later, but please add a comment here.

> 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;

I'd prefer shorter names for local variables.

> +
>      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)) {

Equivalent but shorter:
        ~bridge_control & bridge_control_new & PCI_BRIDGE_CTL_BUS_RESET

> +        /* 0 -> 1 */
> +        pci_bus_reset(&s->sec_bus);
> +    }
>  }
>  
>  void pci_bridge_disable_base_limit(PCIDevice *dev)
> -- 
> 1.7.1.1