Intel Extensible Firmware Interface - Manual (Page 484)

Extensible Firmware Interface Specification
12-66 12/01/02 Version 1.10
Value The comparison value used for the polling exit criteria.
Delay The number of 100 ns units to poll. Note that timer available may
be of poorer granularity.
Result Pointer to the last value read from the memory location.
Description
This function provides a standard way to poll a PCI memory location. A PCI memory read
operation is performed at the PCI memory address specified by
BarIndex and Offset for the
width specified by Width . The result of this PCI memory read operation is stored in Result .
This PCI memory read operation is repeated until either a timeout of Delay 100 ns units has
expired, or ( Result & Mask) is equal to Value .
This function will always perform at least one memory access no matter how small Delay may be.
If Delay is 0, then Result will be returned with a status of EFI_SUCCESS even if Result
does not match the exit criteria. If Delay expires, then EFI_TIMEOUT is returned.
If Width is not EfiPciIoWidthUint8 , EfiPciIoWidthUint16 ,
EfiPciIoWidthUint32 , or EfiPciIoWidthUint64 , then EFI_INVALID_PARAMETER
is returned.
The memory operations are carried out exactly as requested. The caller is responsible for satisfying
any alignment and memory width restrictions that a PCI controller on a platform might require. For
example on some platforms, width requests of
EfiPciIoWidthUint64 do not work.
All the PCI transactions generated by this function are guaranteed to be completed before this
function returns. However, if the memory mapped I/O region being accessed by this function has
the
EFI_PCI_ATTRIBUTE_MEMORY_CACHED attribute set, then the transactions will follow the
ordering rules defined by the processor architecture.
Status Codes Returned
EFI_SUCCESS The last data returned from the access matched the poll exit criteria.
EFI_INVALID_PARAMETER Width is invalid.
EFI_INVALID_PARAMETER Result is NULL .
EFI_UNSUPPORTED BarIndex not valid for this PCI controller.
EFI_UNSUPPORTED Offset is not valid for the BarIndex of this PCI controller.
EFI_TIMEOUT Delay expired before a match occurred.
EFI_OUT_OF_RESOURCES The request could not be completed due to a lack of resources.