DMA Address

i need to physical RAM memory test, in that case i need to skip DMA address,Can you please tell me, how to find out DMA address which is mapped with physical memory and skip that physical address. i am want to add this code into my module.I am using linux 3.12 kernel.

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pettitda over 9 years ago in reply to Former Member +1

If you're serious about testing the physical memory, then you need to do it before Linux is loaded. For example, if you are using uBoot for a bootloader then you would do the memory test there or even…

0 Former Member over 9 years ago

i need to physical RAM memory test, in that case i dont want to check DMA pages,how to find out DMA pages.how its allocated in physical ram ? if it is allocated in physical RAM. Testing RAm then i need to skip DMA pages. how to do that please let me known.
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0 clem57 over 9 years ago

Using DMESG look for:
Virtual kernel memory layout:
    vector : 0xffff0000 - 0xffff1000   (   4 kB)
    fixmap : 0xfff00000 - 0xfffe0000   ( 896 kB)
    DMA     : 0xfbe00000 - 0xffe00000   ( 64 MB)
    vmalloc : 0xd9800000 - 0xf2000000   ( 392 MB)
    lowmem : 0xc0000000 - 0xd9000000   ( 400 MB)
    pkmap   : 0xbfe00000 - 0xc0000000   (   2 MB)
    modules : 0xbf000000 - 0xbfe00000   ( 14 MB)
      .init : 0xc0008000 - 0xc0047000   ( 252 kB)
      .text : 0xc0047000 - 0xc08cde00   (8732 kB)
      .data : 0xc08ce000 - 0xc095c890   ( 571 kB)
       .bss : 0xc095c8b4 - 0xc0ae4448   (1567 kB)

Clem
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0 clem57 over 9 years ago in reply to clem57

Then use https://www.kernel.org/doc/gorman/pdf/understand.pdf to translate
C
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0 Former Member over 9 years ago in reply to clem57

HI Sir,

Thanks for your reply. but i write module in that i need to check physical memory. i test with 32 bit address at a time. example i will take address from page_align macro and passed it. first thing if that address is DMA address then i need to skip that address for that i want to write code.
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0 pettitda over 9 years ago in reply to Former Member

If you're serious about testing the physical memory, then you need to do it before Linux is loaded. For example, if you are using uBoot for a bootloader then you would do the memory test there or even lower if you have another layer under uBoot.
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0 tusharp over 9 years ago

does this help ??

https://community.freescale.com/docs/DOC-96412
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