USB Host Controller Access to System Memory
14-83
Universal Serial Bus Host
Figure 14–34. Relationships Between Processor Virtual Address, Processor Physical
Address, and Local Bus Virtual Address with Local Bus MMU Enabled
Processor
physical
address
Local Bus
virtual
address
Local bus
MMU
0x00000000
0x30000000
0x3FFFFFFF
0x2FFFFFFF
0x40000000
0xFFFFFFFF
0x00000000
0xFFFFFFFF
Processor
virtual
address
Processor
MMU
0x00000000
0xFFFFFFFF
If any portion of the USB host controller data structures are stored in memory
that is not in the physical address range 0x00000000 to 0x0FFFFFFF, then the
local bus MMU must be programmed to provide a different mapping between
local bus virtual addresses and physical addresses. A system implementation
that does not implement any physical RAM in the physical address range
0x00000000 to 0x0FFFFFFF must enable the local bus MMU in order to use
the OMAP5910 USB host controller.
Initialization of the local bus MMU is done using the same sorts of operations
as are used for initializing the MPU MMU, except addressing the local bus
MMU instead of the MPU MMU.
The processor local bus interface ignores any local bus activity in the local bus
virtual address range from 0x0 to 0x2FFFFFFF, and the local bus virtual
address range from 0x40000000 to 0xFFFFFFFF. Should the USB host
request such an access (through improper setup of the USB host controller
registers or improper initialization of endpoint descriptors, transfer descriptors,
or the HCCA), the USB host local bus interface times out and signals an