cachemode.s

此压缩包为杰得开发得z228的BSP的源代码,可以实现很多功能,尤其是视频解码有很好的效果.

;
;   The content of this file or document is CONFIDENTIAL and PROPRIETARY
;   to Jade Technologies Co., Ltd.  It is subjected to the terms of a
;   License Agreement between Licensee and Jade Technologies Co., Ltd.
;   restricting among other things, the use, reproduction, distribution
;   and transfer.  Each of the embodiments, including this information 
;   and any derivative work shall retain this copyright notice.
; 
;   Copyright (c) 2004 - 2005 Jade Technologies Co., Ltd. 
;   All rights reserved.
; ----------------------------------------------------------------
; File:     cachemode.s,v
; Revision: 1.0
; ----------------------------------------------------------------
; $

    OPT     2       ; disable listing
    INCLUDE kxarm.h
    OPT     1       ; reenable listing
    OPT     128     ; disable listing of macro expansions
    INCLUDE armmacros.inc

    TEXTAREA

    LEAF_ENTRY OEMARMCacheMode
;++
; Routine Description:
;    Sets the C and B bits to be used to build page tables
;
; C and B bits are part of the page table entries and control write through 
; vs. write back cache modes, cacheability, and write buffer use. 
;
; *** Note: The C and B bit functionality is processor specific. Consult the 
; CPU hardware manual for the CPU in question before altering these bit 
; configurations. ***
;
; This default configuration (C=B=1)works on all current ARM CPU's and gives
; the following behaviour
; ARM92x: write back cache mode
;
; The four valid options are:
;   ARM_NoBits      0x00000000
;   ARM_CBit        0x00000008
;   ARM_BBit        0x00000004
;   ARM_CBBits      0x0000000C
;
; Syntax:
;   DWORD OEMARMCacheMode(void);
;
; Arguments:
;   -- none --
;
; Return Value:
;  r0 must contain the desired C and B bit configuration. See description above
;  for valid bit patterns.
;
; Caution:
;  The value placed in r0 MUST be an immediate data value and NOT a predefined
;  constant. This function is called at a point in the boot cycle where the 
;  memory containing predefined constants has NOT been initialized yet.
;  --
        mov r0, #0x0C   ; Default is writeback cached. Earlier versions of Windows CE
                        ; gave better performance with writethrough and no explicit
                        ; cache flushing; now that the frequency of cache flushing is
                        ; much lower, writeback is better.

        RETURN

        END