82598EB Datasheet, PDF (136/596 Pages) Intel Corporation – Intel® 82598EB 10 Gigabit Ethernet Controller Datasheet

Intel^® 82598EB 10 GbE Controller - Power Management and Delivery
packets directed to the old configuration of the queue. For example, VM goes down and a different VM
gets the queue (if there were undrained packets) these packets targeted to the previous VM would get
to the new VM that owns the queue.
The receive path can be disabled only after all the receive queues are disabled.
3.2.3.2.7 Transmit Initialization
The following should be done once per transmit queue:
• Allocate a region of memory for the transmit descriptor list.
• Program the descriptor base address with the address of the region.
• Set the length register to the size of the descriptor ring.
• Initialize the transmit descriptor registers (TDBAL, TDBAH, TDL).
• Program the Transmit Descriptor Control registers with the desired TX descriptor write back
policy. Suggested values are:
—WTHRESH = 1b
—All other fields 0b.
—Enable queue using TXDCTL.ENABLE
—Poll the Queue Enable bit to make sure the queue is enabled (read TXDCTL.Qx.25; check that it
is set).
3.2.3.2.8 Dynamic Enabling and Disabling of Transmit Queues
Transmit queues can be enabled or disabled dynamically if the following procedure is followed.
1. Enabling:
a. Follow the per queue initialization described in the previous section.
2. Disabling:
a. Stop storing packets for transmission in this queue.
b. Wait until the head of the queue TDH equals the tail TDT – indicates the queue is empty.
c. Wait until all descriptors are written back (polling DD bit in ring or polling the Head_WB content).
It might be required to flush the transmit queue by setting the TXDCTL[n].SWFLSH if the RS bit
in the last fetched descriptor is not set or if WTHRESH is greater than zero.
d. Disable the queue by clearing TXDCTL.ENABLE.
The transmit path can be disabled only after all transmit queue are disabled.
3.3
Power Management and Delivery
This section describes how power management is implemented in the 82598.
3.3.1 Power Delivery
The 82598’s power is delivered through external voltage regulators. Refer to Section 8. for more
details.
136