Texas Instruments OMAP5912 Reference Manual page 1357

2.11.1 MPUVAtoPA()—MPU Virtual Address to Physical Address Conversion
Function
2.11.2 PAtoMPUVA()—Physical Address to MPU Virtual Address Conversion
Function
2.12 NULL Pointers
2.13 OMAP5912 OCPI Bus and the USB Host Controller
SPRU761A
descriptor that has been retired. This requires that the host controller driver
software must be able to convert from the physical address back to an MPU
virtual address.
Several address conversion functions are helpful to enable proper addressing
by the MPU software and the USB host controller. The functionality required
for proper address conversion depends on the settings used in the MPU MMU,
so it is system-dependent. The conversion functions are described in general
terms in the following subsections.
This function converts an MPU virtual address to the equivalent system
physical address. This function must understand the way that the system
software has configured the MPU MMU. This function must provide a
conversion that has a result that is identical to the conversion done in hardware
by the MPU MMU.
This function is a reverse version of the MPU virtual address to physical
address conversion. It accepts a physical address as an argument and returns
the equivalent MPU virtual address.
It is possible to program the MPU MMU to allow two (or more) different MPU
virtual addresses to map to the same physical address. This is especially
common in systems that use linear addressing within a task. System software
implementers must be careful to avoid that situation or to perform the
conversion in a way that understands the task-specific conversion
requirements.
The OHCI Specification for USB uses NULL pointers to indicate the end of a
list. The OMAP USB host controller compares the ED and TD pointers against
the value 0x00000000 to determine if the pointer is a null pointer. Address
conversion routines must understand this usage.
The OMAP5912 OCPI bus provides a mechanism whereby OMAP5912
peripheral modules can access system memory. Unlike peripherals that use
USB Host Controller
Universal Serial Bus (USB) 65