Intel manual 27.5.4 PCI, Intel IXP400 Software OS Abstraction, ATM and HSS

Intel® IXP400 Software

Endianness in Intel® IXP400 Software

•IX_OSAL_MBUF word pointers must be swapped prior to submission to the NPE. (ixEthAccPortTxFrameSubmit())

Note: The IX_OSAL_MBUF chain is walked and all IX_OSAL_MBUFs in a chain are updated. (ixEthAccPortRxFreeReplenish())

•IX_OSAL_MBUF word pointers are swapped on reception from the NPE before calling:

—User functions registered via ixEthAccPortTxDoneCallbackRegister.

—User function registered via ixEthAccTxBufferDoneCallbackRegister.

•Ethernet Database (IxEthDB)

—Endianness conversion of the Ethernet learning trees when ownership is transferred to/ from the XScale <-> Ethernet NPEs.

—Tree Writes. ixEthDBNPETreeWrite

—Tree uploads. ixEthDBNPESyncScan

—Display. ixEthELTDumpTree

•MAC Statistics. The memory used to return statistics from the NPE is endian-converted before returning the data.

•Ethernet MAC registers are mapped in Little-Endian Data Coherent mode.

Note: The coherency modes chosen for IXP400 software Little-Endian implementations for VxWorks are summarized in “Endian Conversion Macros” on page 362.

27.5.3.5ATM and HSS

Both ATM and HSS components pass descriptors between the Intel XScale core and NPEs. These descriptors undergo similar changes to those described above.

27.5.4PCI

The primary consideration for PCI network drivers is the configuration of the byte swapping within the PCI controller itself (see “Endian Hardware Summary” on page 352).

The configuration is dependent on the coherency mode of the SDRAM memory area. In case of VxWorks, the SDRAM memory controller is in Data Coherent mode.

Importantly, the PCI memory space must be configured in Little-Endian Data Coherent mode. This is the physical memory area 0x4800,0000.

The PCI Configuration Space Register has PCI_CSR_IC, PCI_CSR_ABE, PCI_CSR_PDS, PCI_CSR_ADS set to ‘1’.

27.5.5Intel® IXP400 Software OS Abstraction

All Little-Endian system configuration information is in the ixp_osal\os

Programmer’s Guide	IXP400 Software Version 2.0	April 2005
	Document Number: 252539, Revision: 007	361