Pci Configuration Registers; Msi Address; Msi Data; Figure 52: Msi Data Field - Broadcom NetXtreme/NetLink BCM5718 Series Programmer's Manual

BCM5718 Programmer's Guide
• DMAs data of received packets to the host.
• DMAs receive buffer descriptors to receive return ring in the host memory.
• DMAs status block to the host memory.
• Writes specified DWORD data to specified host address.
In this mode, the Ethernet controller writes DWORD data to specified host address instead of generating an
interrupt. The specified data and address are configurable. The specified address is typically a memory-mapped
IO port within the PCI host bridge. The PCI host bridge is the gateway to the main memory controller. This
means that the DWORD data write (MSI message) to PCI host bridge is in the posted write buffers and was
posted after the writes for the status block update. It is the rule that PCI host bridge must perform posted writes
in the same order that they were received. This means that by the time MSI message arrives at the PCI host
bridge, the status block has already been posted to the host memory. Upon receipt of the MSI message write,
the PCI host bridge generates the interrupt request to the processor. Interrupt service routine of the device driver
is invoked. It is not necessary to do a dummy read because updated status block is already in the host memory.

PCI Configuration Registers

Operating system/system software can configure the specified DWORD data and specified 64-bit host address
for the device with MSI_DATA (Offset 0x64) and MSI_Address register (Offset 0x5c), respectively.

MSI Address

This is a 64-bit field. MSI address at offset 0x5c and 0x60 should be programmed with the low-order and high-
order bits of the 64-bit physical address. If the host only supports 32-bit physical address, the high-order address
should be programmed with zeros.

MSI Data

This is a 16-bit field. The least significant three bits can be modified by the Ethernet controller when it writes MSI
message to host. The DWORD data for the MSI message is depicted as shown in
Broadcom
®
January 29, 2016 • 5718-PG108-R

Figure 52: MSI Data FIeld

All 0's
Figure
16-bit MSI_Data
MSI
52.
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