diff options
Diffstat (limited to 'arch/powerpc/platforms/powernv/pci.h')
| -rw-r--r-- | arch/powerpc/platforms/powernv/pci.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h index 20941ef2706e..fc05f9b5caed 100644 --- a/arch/powerpc/platforms/powernv/pci.h +++ b/arch/powerpc/platforms/powernv/pci.h @@ -33,6 +33,24 @@ enum pnv_phb_model { #define PNV_IODA_PE_SLAVE (1 << 4) /* Slave PE in compound case */ #define PNV_IODA_PE_VF (1 << 5) /* PE for one VF */ +/* + * A brief note on PNV_IODA_PE_BUS_ALL + * + * This is needed because of the behaviour of PCIe-to-PCI bridges. The PHB uses + * the Requester ID field of the PCIe request header to determine the device + * (and PE) that initiated a DMA. In legacy PCI individual memory read/write + * requests aren't tagged with the RID. To work around this the PCIe-to-PCI + * bridge will use (secondary_bus_no << 8) | 0x00 as the RID on the PCIe side. + * + * PCIe-to-X bridges have a similar issue even though PCI-X requests also have + * a RID in the transaction header. The PCIe-to-X bridge is permitted to "take + * ownership" of a transaction by a PCI-X device when forwarding it to the PCIe + * side of the bridge. + * + * To work around these problems we use the BUS_ALL flag since every subordinate + * bus of the bridge should go into the same PE. + */ + /* Indicates operations are frozen for a PE: MMIO in PESTA & DMA in PESTB. */ #define PNV_IODA_STOPPED_STATE 0x8000000000000000 |