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SDRAM mapping?

Posted on 2003-11-18
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Last Modified: 2013-12-15
I am involved in an embedded project. How would I tell my linux kernel about the presence of 32MB SDRAM?
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Question by:Johncy
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6 Comments
 
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Expert Comment

by:dimitry
ID: 9775755
Your bootloader may pass this to the kernel. For example through redboot you can pass to the kernel:
"root=/dev/mtdblock3 mem=32M"
So with the help of mem=sizeM you may "tell" to kernel size of your SDRAM.
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Author Comment

by:Johncy
ID: 9775921
Thanks for your suggestion. How about the physical address mapping of the SDRAM to the processor?
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LVL 11

Expert Comment

by:dimitry
ID: 9780883
Take a look on file arch.c under ~/arch/CPUNAME/kernel and you will find:
Function somename_fixup(...,struct meminfo *mi)
{
        mi->nr_banks      = 1;
        mi->bank[0].start = PHYS_OFFSET;  /* <--SDRAM phyical address */
        mi->bank[0].size  = (32*1024*1024);  /* <-- SDRAM size */
        mi->bank[0].node  = 0;
        ...
}
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Author Comment

by:Johncy
ID: 9793866
I could find such a file for ARM but no such file arch.c in arch/i386/kernel. Where could i get the information for x86 architecture?
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Author Comment

by:Johncy
ID: 9983713
Please tell me about the SDRAM mapping address for the kernel.
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Accepted Solution

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dimitry earned 40 total points
ID: 9985614
Take a look on following documentation:
 - src/arch/i386/mm/init.c
   function mem_init()
 - src/Documentation/IO-mapping.txt
 - src/Documentation/i386/boot.txt

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