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3.8.9
CardBus Bridge Power Management
The
PCI Bus Power Management Interface Specification for PCI to CardBus Bridges
was approved by PCMCIA in
December of 1997. This specification follows the device and bus state definitions provided in the
PCI Bus Power
Management Interface Specification
published by the PCI Special Interest Group (SIG). The main issue addressed
in the
PCI Bus Power Management Interface Specification for PCI to CardBus Bridges
is wake-up from D3
hot
or D3
cold
without losing wake-up context (also called PME context).
The specific issues addressed by the
PCI Bus Power Management Interface Specification for PCI to CardBus Bridges
for D3 wake-up are as follows:
Preservation of device context. The specification states that a reset must occur during the transition from
D3 to D0. Some method to preserve wake-up context must be implemented so that the reset does not clear
the PME context registers.
Power source in D3
cold
if wake-up support is required from this state.
The Texas Instruments PCI6515 controller addresses these D3 wake-up issues in the following manner:
Two resets are provided to handle preservation of PME context bits:
Global reset (GRST) is used only on the initial boot up of the system after power up. It places the
PCI6515 controller in its default state and requires BIOS to configure the controller before becoming
fully functional.
PCI reset (PRST) has dual functionality based on whether PME is enabled or not. If PME is enabled,
then PME context is preserved. If PME is not enabled, then PRST acts the same as a normal PCI reset.
Please see the master list of PME context bits in Section 3.8.11.
Power source in D3
cold
if wake-up support is required from this state. Since V
CC
is removed in D3
cold
, an
auxiliary power source must be supplied to the PCI6515 V
CC
terminals. Consult the
PCI14xx
Implementation Guide for D3 Wake-Up
or the
PCI Power Management Interface Specification for PCI to
CardBus Bridges
for further information.
3.8.10 ACPI Support
The
Advanced Configuration and Power Interface (ACPI) Specification
provides a mechanism that allows unique
pieces of hardware to be described to the ACPI driver. The PCI6515 controller offers a generic interface that is
compliant with ACPI design rules.
Two doublewords of general-purpose ACPI programming bits reside in PCI6515 PCI configuration space at offset
88h. The programming model is broken into status and control functions. In compliance with ACPI, the top level event
status and enable bits reside in the general-purpose event status register (PCI offset 88h, see Section 4.31) and
general-purpose event enable register (PCI offset 89h, see Section 4.32). The status and enable bits are
implemented as defined by ACPI and illustrated in Figure 315.
Event Output
Event Input
Enable Bit
Status Bit
Figure 315. Block Diagram of a Status/Enable Cell
The status and enable bits generate an event that allows the ACPI driver to call a control method associated with the
pending status bit. The control method can then control the hardware by manipulating the hardware control bits or
by investigating child status bits and calling their respective control methods. A hierarchical implementation would
be somewhat limiting, however, as upstream devices would have to remain in some level of power state to report
events.
For more information of ACPI, see the
Advanced Configuration and Power Interface (ACPI) Specification.