USB Open Host Controller Interface Functionality
14-7
Universal Serial Bus Host
14.2.3 OMAP5910 Implementation of OHCI Specification for USB
14.2.3.1
Isochronous TD OFFSETX/PSWX Values
The OMAP5910 USB host controller implements the OHCI Specification for
USB optional feature of checking isochronous OFFSETX/PSWX values. If
either OFFSETX or OFFSET(X+1) does not have a condition code of Not
Accessed, or if the OFFSET(X+1) value is not greater than or equal to
OFFSETX, then an unrecoverable Error is reported. Unrecoverable errors
issued for these reasons do not cause an update of the HostUEAddr,
HostUEStatus, or HostTimeoutCtrl registers.
14.2.3.2
OMAP5910 USB Host Controller Endpoint Descriptor (ED) List Head Pointers
The OHCI Specification for USB provides a specific sequence of operations
for the host controller driver to perform when setting up the host controller.
Failure to follow that sequence can result in malfunction. As a specific
example, the HcControlHeadED and HCBulkHeadED pointer registers and
the 32 HccaInterruptTable pointers must all point to valid local bus addresses
of valid endpoint descriptors.
The OMAP5910 USB host controller does not check HcControlHeadED regis-
ters, HcBulkHeadED registers, or the values in the 32 HccaInterruptTable
pointers before using them to access EDs. If any of these pointers are NULL
when the corresponding list enable bit is set, the OMAP5910 USB host control-
ler attempts to access using the local bus virtual address of 0, which
causes an unrecoverable error. Registers HostUEAddr, HostUEStatus, and
HostTimeoutCtrl are updated in this case.
