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/*
* (C) Copyright 2010
* Graeme Russ <graeme.russ@gmail.com>.
*
* See file CREDITS for list of people who contributed to this
* project.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
*/
#include <config.h>
#include <asm/processor-flags.h>
#include <asm/ic/sc520.h>
.section .text
.globl car_init
car_init:
/*
* How to enable Cache-As-RAM for the AMD Elan SC520:
* 1. Turn off the CPU Cache (may not be strictly required)
* 2. Set code execution PAR (usually the BOOTCS region) to be
* non-cachable
* 3. Create a Cachable PAR Region for an area of memory which is
* a) NOT where the code is being executed
* b) NOT SDRAM (Controller not initialised yet)
* c) WILL response to read requests
* The easiest way to do this is to create a second BOOTCS
* PAR mappnig with an address != the PAR in step 2
* 4. Issue a wbinvd to invalidate the CPU cache
* 5. Turn on the CPU Cache
* 6. Read 16kB from the cached PAR region setup in step 3
* 7. Turn off the CPU Cache (but DO NOT issue a wbinvd)
*
* The following code uses PAR2 as the cached PAR (PAR0 and PAR1
* are avoided as these are the only two PARs which can be used
* as PCI BUS Memory regions which the board might require)
*
* The configuration of PAR2 must be set in the board configuration
* file as CONFIG_SYS_SC520_CAR_PAR
*/
/* Configure Cache-As-RAM PAR */
movl $CONFIG_SYS_SC520_CAR_PAR, %eax
movl $SC520_PAR2, %edi
movl %eax, (%edi)
/* Trash the cache then turn it on */
wbinvd
movl %cr0, %eax
andl $~(X86_CR0_NW | X86_CR0_CD), %eax
movl %eax, %cr0
/*
* The cache is now enabled and empty. Map a region of memory to
* it by reading that region.
*/
movl $CONFIG_SYS_CAR_ADDR, %esi
movl $CONFIG_SYS_CAR_SIZE, %ecx
shrl $2, %ecx /* we are reading longs */
cld
rep lodsl
/* Turn off the cache, but don't trash it */
movl %cr0, %eax
orl $(X86_CR0_NW | X86_CR0_CD), %eax
movl %eax, %cr0
/* Clear the CAR region */
xorl %eax, %eax
movl $CONFIG_SYS_CAR_ADDR, %edi
movl $CONFIG_SYS_CAR_SIZE, %ecx
shrl $2, %ecx /* we are writing longs */
rep stosl
/*
* Done - We should now have CONFIG_SYS_CAR_SIZE bytes of
* Cache-As-RAM
*/
jmp car_init_ret
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