ARM ARM1176JZF-S Technical Reference Manual page 215

ARM DDI 0301H
ID012310
Note
The VA that this operation uses is the true VA not the MVA.
VA to PA translation in the other world
The purpose of the VA to PA translation in the other world is to translate the address with the
current virtual mapping in the Non-secure world while the core is in the Secure world.
The VA to PA translation in the other world operations use:
• CP15 c7
• four, 32-bit write-only operations in the Secure world only
• operations accessible in privileged modes only.
The operations work in the Secure world for Non-secure privileged or Non-secure User access
permissions and returns information in the PA Register for aborts, when the translation is
unsuccessful, or page table information, when the translation succeeds.
Attempts to access the VA to PA translation operations in the other world in any Non-secure or
User mode result in an Undefined exception.
To use the VA to PA translation in the other world write CP15 c7 with:
• Opcode_1 set to 0
• CRn set to c7
• CRm set to c8
• Opcode_2 set to:
— 4 for privileged read permission
— 5 for privileged write permission
— 6 for User read permission
— 7 for User write permission.
General register <Rn> contains the VA for translation. The result returns in the PA Register, for
example:
MCR p15,0,<Rn>,c7,c8,4
MRC p15,0,<Rd>,c7,c4,0
Data Synchronization Barrier operation
The purpose of the Data Synchronization Barrier operation is to ensure that all outstanding
explicit memory transactions complete before any following instructions begin. This ensures
that data in memory is up to date before the processor executes any more instructions.
Note
The Data Synchronization Barrier operation is synonymous with Drain Write Buffer and Data
Write Barrier in earlier versions of the architecture.
The Data Synchronization Barrier operation is:
• in CP15 c7
• 32-bit write-only access, common to both Secure and Non-secure worlds
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;get VA = <Rn> and run Non-secure translation
;with Non-secure privileged read permission.
;if the selected page table has the
;privileged read permission, the PA is loaded
;in PA register, otherwise abort information is
;loaded in PA Register
;read in <Rd> the PA value
System Control Coprocessor
3-83