
IDT Power Management
PES32NT24xG2 User Manual
9 - 4
January 30, 2013
Notes
• This requires transitioning the link to the L0 state when error reporting is enabled and the link is
not in L0.
–
Error messages resulting from any event other than the receipt of a TLP are discarded (i.e., no
error message is generated).
–
All received completions that target the DMA function are treated as unexpected completions
(UC).
–
Note that the DMA function does not automatically quiesce traffic as a result of being placed in
D3
hot
. It is the responsibility of software (e.g., the DMA driver) to ensure that the DMA function is
properly quiesced prior to entry into D3
hot
.
Power Management Event (PME) Messages
The PES32NT24xG2 does not support generation of PME messages from the D3
cold
state. PME
message generation is only supported by downstream switch ports (i.e., the PCI-to-PCI bridge, NT function,
and DMA function associated with an upstream port do not support PME message generation).
Downstream switch ports support the generation of hot-plug PME events (i.e., a PM_PME power
management message) from the D3
hot
state (see section Hot-Plug Events on page 11-7). This includes
both the case when the downstream switch port is in the D3
hot
state or the entire switch partition is in the
D3
hot
state.
PCI Express Power Management Fence Protocol
The root complex takes the following steps to turn off power to a system.
–
The root places all devices in the D3 state
–
Upon entry to D3, all devices transition their links to the L1 state
–
The root broadcasts a PME_Turn_Off message.
• The links temporarily transition to L0 in order to transfer the message.
–
Devices acknowledge the PME_Turn_Off message by returning a PME_TO_ACK message
• After transmitting a PME_TO_ACK, a device places its link in L2/L3-Ready state.
The PME_Turn_Off / PME_TO_Ack protocol may be initiated by the root when the switch function’s are
in any power management state. The port’s handling of the power management fence protocol depends on
its operating mode as described below.
Upstream Switch Port or Downstream Switch Port Mode
–
When a port configured in upstream switch port mode receives a PME_Turn_Off message, it
broadcasts the PME_Turn_Off message on all downstream switch ports of the associated parti-
tion. The upstream port transmits a PME_TO_Ack message and transitions its link state to L2/L3
Ready after it has received a PME_TO_Ack message on each of the downstream switch ports of
the partition. This process is called PME_TO_Ack aggregation.
• In the PES32NT24xG2, the link is considered down in the L2/L3 Ready state (see section Link
States on page 7-9). This allows a power management turn-off event in a partition to be signaled
via the event signaling mechanism (see Chapter 16, Switch Events).
–
The aggregation of PME_TO_Ack messages on downstream switch ports is abandoned by the
upstream switch port when this port receives a TLP after having previously received a
PME_Turn_Off message but before having responded with a PME_TO_Ack message. Once a
PME_TO_Ack message has been scheduled for transmission on the upstream switch port and
the PME_TO_Ack aggregation process has completed, received TLPs at that point are discarded.
–
If the TLP that causes PME_TO_Ack aggregation to be abandoned targets a PES32NT24xG2
function, then the targeted function responds to the TLP normally. If the TLP that causes aggre-
gation to be abandoned is routed to a downstream switch port’s link and the link is in L0, then the
TLP is transmitted on the downstream switch port. If the downstream switch port’s link is not in L0
(e.g., it is in L2/L3 Ready), then the port transitions the link to Detect and then to L0. Once the link
is reaches L0, the TLP is transmitted on the downstream switch port.
Содержание PCI Express 89HPES32NT24xG2
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Страница 24: ...IDT List of Tables PES32NT24xG2 User Manual xiv January 30 2013 Notes...
Страница 28: ...IDT List of Figures PES32NT24xG2 User Manual xviii January 30 2013 Notes...
Страница 56: ...IDT PES32NT24xG2 Device Overview PES32NT24xG2 User Manual 1 20 January 30 2013 Notes...
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Страница 170: ...IDT Power Management PES32NT24xG2 User Manual 9 6 January 30 2013 Notes...
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