How do I set up TLB in MMU on 9p9215 for memory mapped I/O?

Embedded Devices
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1

I’m porting an application from a 7u 7520 module to a 9p 9215 module. It uses memory mapped I/O to access an FPGA. There’s no MMU on the 7u, so as part of the port I need to add code to set up the MMU. I customized the code for CS3 in connectcore9p9215_a/cs.c to set up the Memory controller and to set the Base and Mask registers. I have read the MMU section of the 9p9215 Hardware Reference, but I could really use some sample code that sets up the MMU. The FPGA has 8 address bits and 8 data bits, so a 1KB page would be big enought.

2

bsp\platforms\connectcore9p9215_a\customizeCache.c:

/ad

  • MMU Definition Table
  • You should edit this table to reflect the address map of your application.
  • The BSP processes this table at startup to build the MMU address
  • translation table. This table determines the access level and caching
  • options for each section of memory.
  • Each entry in this table specifies a section of the processor’s address space
  • and sets the MMU options for it. Any sections of memory that do not have
  • an entry in this table are defined as nonaccessable. Any attempt to access
  • such a region will cause an abort exception.
  • The NASetCacheAccessModes() function can be used to modify the cache and user
  • access settings for a region of memory after the MMU address translation table
  • has been setup. The page size for regions set in this table cannot be
  • modified at runtime.
  • Refer to the documentation on mmuTableType for details on how to create
  • entries.
  • @external
  • @category MMU
  • @since 6.1
  • @note Use large page sizes to improve performance.
  •    The MMU has a small internal cache of MMU table

  •    entries.  As long as the table entry for the memory being accessed is

  •    inside the MMU's internal cache, the MMU does not have to scan the

  •    MMU table in RAM.  However, whenever the CPU accesses memory whose

  •    table entry is not already in the MMU's cache, the MMU has to look up the 

  •    table entry in RAM.  This incurs at least one extra memory access 

  •    (more for coarse sections) for the access.  The more table entries 

  •    there are, the more likely this is to happen.
  • @see @link mmuCacheModeValues
  • @see @link mmuUserAccessValues
  • @see @link mmuPageSizes
  • @see @link mmuTableType
  • @see @link NASetCacheAccessModes
    ad/
    mmuTableType mmuTable[] =
    {
    /* Start End Page Size Cache Mode User Access Physical Address /
    /     ========== ========== ================ ============= =========== =============== /
    {0x00000000, 0x00ffffff, MMU_PAGE_SIZE_1M, MMU_WRITE_BACK, MMU_CLIENT_RW, 0x00000000, 0x00ffffff}, /     16 Megs of RAM /
    …
    …
    …
    {0xC0000000, 0xC0ffffff, MMU_PAGE_SIZE_1M, MMU_BUFFERED, MMU_CLIENT_RW, 0x00000000, 0x00ffffff} /     Uncached SDRAM */
    };

Just add an entry to that table.