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93 lines
2.8 KiB
ArmAsm
93 lines
2.8 KiB
ArmAsm
/*
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* (C) Copyright 2010-2011
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* Graeme Russ, <graeme.russ@gmail.com>
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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#include <config.h>
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#include <asm/processor-flags.h>
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#include <asm/ic/sc520.h>
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.section .text
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.globl car_init
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car_init:
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/*
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* How to enable Cache-As-RAM for the AMD Elan SC520:
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* 1. Turn off the CPU Cache (may not be strictly required)
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* 2. Set code execution PAR (usually the BOOTCS region) to be
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* non-cachable
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* 3. Create a Cachable PAR Region for an area of memory which is
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* a) NOT where the code is being executed
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* b) NOT SDRAM (Controller not initialised yet)
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* c) WILL response to read requests
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* The easiest way to do this is to create a second BOOTCS
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* PAR mappnig with an address != the PAR in step 2
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* 4. Issue a wbinvd to invalidate the CPU cache
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* 5. Turn on the CPU Cache
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* 6. Read 16kB from the cached PAR region setup in step 3
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* 7. Turn off the CPU Cache (but DO NOT issue a wbinvd)
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*
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* The following code uses PAR2 as the cached PAR (PAR0 and PAR1
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* are avoided as these are the only two PARs which can be used
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* as PCI BUS Memory regions which the board might require)
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*
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* The configuration of PAR2 must be set in the board configuration
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* file as CONFIG_SYS_SC520_CAR_PAR
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*/
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/* Configure Cache-As-RAM PAR */
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movl $CONFIG_SYS_SC520_CAR_PAR, %eax
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movl $SC520_PAR2, %edi
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movl %eax, (%edi)
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/* Trash the cache then turn it on */
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wbinvd
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movl %cr0, %eax
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andl $~(X86_CR0_NW | X86_CR0_CD), %eax
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movl %eax, %cr0
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/*
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* The cache is now enabled and empty. Map a region of memory to
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* it by reading that region.
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*/
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movl $CONFIG_SYS_CAR_ADDR, %esi
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movl $CONFIG_SYS_CAR_SIZE, %ecx
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shrl $2, %ecx /* we are reading longs */
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cld
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rep lodsl
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/* Turn off the cache, but don't trash it */
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movl %cr0, %eax
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orl $(X86_CR0_NW | X86_CR0_CD), %eax
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movl %eax, %cr0
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/* Clear the CAR region */
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xorl %eax, %eax
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movl $CONFIG_SYS_CAR_ADDR, %edi
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movl $CONFIG_SYS_CAR_SIZE, %ecx
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shrl $2, %ecx /* we are writing longs */
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rep stosl
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/*
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* Done - We should now have CONFIG_SYS_CAR_SIZE bytes of
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* Cache-As-RAM
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*/
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jmp car_init_ret
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