diff options
Diffstat (limited to 'arch/x86/cpu/sc520/sc520_car.S')
| -rw-r--r-- | arch/x86/cpu/sc520/sc520_car.S | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/arch/x86/cpu/sc520/sc520_car.S b/arch/x86/cpu/sc520/sc520_car.S new file mode 100644 index 0000000000..a33f94f491 --- /dev/null +++ b/arch/x86/cpu/sc520/sc520_car.S @@ -0,0 +1,93 @@ +/* + * (C) Copyright 2010-2011 + * 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 |
