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6-10 March, 2003 Developer’s Manual
Intel
®
80200 Processor based on Intel
®
XScale
™
Microarchitecture
Data Cache
6.3.3.1 Global Clean and Invalidate Operation
A simple software routine is used to globally clean the data cache. It takes advantage of the
line-allocate data cache operation, which allocates a line into the data cache. This allocation will
evict any dirty data in the cache back to external memory. Example 6-2 shows how the data cache
can be cleaned.
The line-allocate operation does not require physical memory to exist at the virtual address
specified by the instruction, since it does not generate a load/fill request to external memory. Also,
the line-allocate operation does not set the 32 bytes of data associated with the line to any known
value. Reading this data produces unpredictable results.
Example 6-2. Global Clean Operation
; Global Clean/Invalidate THE DATA CACHE
; R1 contains the virtual address of a region of cacheable memory reserved for
; this clean operation.
; R0 is the loop count; Iterate 1024 times which is the number of lines in the
; data cache
;; Macro ALLOCATE performs the line-allocation cache operation on the
;; address specified in register Rx.
;;
MACRO ALLOCATE Rx
MCR P15, 0, Rx, C7, C2, 5
ENDM
MOV R0, #1024
LOOP1:
ALLOCATE R1 ; Allocate a line at the virtual address
; specified by R1.
ADD R1, R1, #32 ; Increment the address in R1 to the next cache line
SUBS R0, R0, #1 ; Decrement loop count
BNE LOOP1
;
; Clean the Mini-data Cache
; Can’t use line-allocate command, so cycle 2KB of unused data through.
; R2 contains the virtual address of a region of cacheable memory reserved for
; cleaning the Mini-data cache
; R0 is the loop count; Iterate 64 times which is the number of lines in the
; Mini-data Cache.
MOV R0, #64
LOOP2:
LDR R3,[R2],#32 ; Load and increment to next cache line
SUBS R0,R0,#1 ; Decrement loop count
BNE LOOP2
;
; Invalidate the data cache and mini-data cache
MCR P15, 0, R0, C7, C6, 0
;