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Altera_Forum
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17 years ago

Linux with MMU on NEEK

Hi, all. I'm testing Linux MMU version, on my NEEK. http://www.nioswiki.com/linux It works fine and I can use "bash" shell. This is the evident proof that we are using the true 'fo...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

Hi,

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OK, I found the manual (http://www.altera.com/literature/hb/nios2/n2cpu_nii51003.pdf), and you are right, bit 31 is not used that way. However, virtual addresses 0xe0000000 and above are are mapped for I/O, skipping the TLB and the cache. So the behavior of ioremap is correct.

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Please be careful, because Wind River guys made a little bit confusing, meaningless and sometimes wrong macros around Nios MMU. For examples, 


/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1994 - 1999, 2000, 03, 04 Ralf Baechle
 * Copyright (C) 2000, 2002  Maciej W. Rozycki
 * Copyright (C) 1990, 1999, 2000 Silicon Graphics, Inc.
 */# ifndef _ASM_NIOS2_GENERIC_SPACES_H# define _ASM_NIOS2_GENERIC_SPACES_H
# include <asm/nios.h>
# define IO_BASE            0xa0000000        <--- ???
#define UNCAC_BASE        0xa0000000    <--- ???
/*
 * This handles the memory map.
 * We handle pages at KSEG0 for kernels with 32 bit address space.
 */# define PAGE_OFFSET        (KERNEL_REGION_BASE + DDR2_TOP_BASE)
/*
 * Memory above this physical address will be considered highmem.
 */# ifndef HIGHMEM_START# define HIGHMEM_START        0x20000000UL# endif
# endif /* _ASM_NIOS2_GENERIC_SPACES_H */
.

Kazu