DMI VCm Resource Control (DMIVCMRCTL_0_0_0_DMIBAR) – Offset 38
DMI VCm Resource Settings
Bit Range | Default | Access | Field Name and Description |
31 | 0x0 | RW | Virtual Channel Enable (VCMEN) 0: Virtual Channel is disabled. 1: Virtual Channel is enabled. See exceptions below. Software must use the VC Negotiation Pending bit to check whether the VC negotiation is complete. When VC Negotiation Pending bit is cleared, a 1 read from this VC Enable bit indicates that the VC is enabled (Flow Control Initialization is completed for the PCI Express port). A 0b read from this bit indicates that the Virtual Channel is currently disabled. [b]BIOS Requirement:[/b] 1. To enable a Virtual Channel, the VC Enable bits for that Virtual Channel must be set in both Components on a Link. 2. To disable a Virtual Channel, the VC Enable bits for that Virtual Channel must be cleared in both Components on a Link. 3. Software must ensure that no traffic is using a Virtual Channel at the time it is disabled. 4. Software must fully disable a Virtual Channel in both Components on a Link before re-enabling the Virtual Channel. |
30:27 | 0h | RO | Reserved |
26:24 | 0x7 | RW | Virtual Channel ID (VCID) Assigns a VC ID to the VC resource. Assigned value must be non-zero. This field can not be modified when the VC is already enabled. |
23:13 | 0h | RO | Reserved |
12:8 | 0x1 | RW/V/L | Save Restore (FC_FSM_STATE) This register is for Save Restore to restore the FC FSM |
7:0 | 0x80 | RO | Traffic Class/Virtual Channel Map (TCVCMMAP) Indicates the TCs (Traffic Classes) that are mapped to the VC resource. Bit locations within this field correspond to TC values. For example, when bit 7 is set in this field, TC7 is mapped to this VC resource. When more than one bit in this field is set, it indicates that multiple TCs are mapped to the VC resource. In order to remove one or more TCs from the TC/VC Map of an enabled VC, software must ensure that no new or outstanding transactions with the TC labels are targeted at the given Link. |