PXA3xx Boot ROM Reference Manual - Marvell

8 Non-Trusted OperationThis section provides usage models for non-trusted boot operation.8.1 Operation with a Non-Trusted Image ModuleOperation with a non-trusted image module (NTIM) provides flexibility in a platform design. Theimage module allows an OEM to reuse the same binary images on both non-trusted and trustedplatforms, which greatly reduces the engineering effort required to support a family of products.The non-trusted image module contains image information that provides some level of checksbefore the image is booted. An image size and Cyclic Redundancy Check (CRC) enable some levelof error detection at boot time. Information about the image size and location enables the OEM bootmodule to grow and change as development continues.If a non-trusted image module is not used, certain restrictions are imposed on the image size by theMarvell ® Trusted Boot ROM. When developing a platform, these restrictions should be consideredcarefully due to differences in compatibility between trusted and non-trusted image modules.8.1.1 NAND FlashThe Trusted Boot ROM supports booting from x8 or x16 NAND devices attached to Chip Select 0 ofthe data flash controller of the processor. Both large- and small-block devices are supported; contactyour Marvell Applications Engineer for information about specific devices.The non-trusted image module is expected to be located in Block 0 at offset 0x0 of the NANDdevice. The Trusted Boot ROM loads the first page of Block 0 and searches for the "TIMH" identifierembedded in the version information of the non-trusted image module. If the structure is found, it isloaded into the internal SRAM of the system. From this point forward, the Trusted Boot ROM usesthe non-trusted image module to load the OEM boot module.The OEM boot module is described by the image information contained in the image informationarray; it is identified by the "OBMI" image identifier. This is the only required identifier for proper usewith the Trusted Boot ROM. Using the information that describes the OEM boot module, the image isloaded from the flash offset pointed to by FlashEntryAddr to the location pointed to byLoadAddr. The number of bytes loaded is determined by the ImageSize entry.After the image has been loaded to the correct address, the CRC must be verified. The image CRCis calculated based on the ImageSize, LoadAddr, and ImageSizeToCRC entries. The calculatedCRC is then compared to the CRC stored in the non-trusted image module, in the CRC field. Upon asuccessful check, control is transferred to the image at the load address.8.1.2 XIP Flash on Chip Select 2The Trusted Boot ROM supports booting from an XIP device attached to Chip Select 2 of theprocessor static memory controller. There is support for several XIP devices; contact your MarvellApplications Engineer for information about specific devices.The non-trusted image module is expected to be located at offset 0x0 of the XIP device. For ChipSelect 2, the XIP device is memory-mapped to 0x1000_0000. This is the address where thenon-trusted image module must reside. The Trusted Boot ROM searches for the "TIMH" identifierembedded in the version information of the non-trusted image module. If the structure is found, it isloaded into the internal SRAM of the system. From this point forward, the Trusted Boot ROM usesthe non-trusted image module to load the OEM boot module.12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758Copyright © 2010 Marvell PUBLIC RELEASE Doc. No. MV-S301208-00 Rev. -Page 81