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Altera_Forum's avatar
Altera_Forum
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20 years ago

Some Define meanings of PK1C20.h file in u-boot

Hi,

In PK1C20.h,

<div class='quotetop'>QUOTE </div>

--- Quote Start ---

/*------------------------------------------------------------------------

* MEMORY ORGANIZATION

* -Monitor at top.

* -The heap is placed below the monitor.

* -Global data is placed below the heap.

* -The stack is placed below global data (&grows down).

*----------------------------------------------------------------------*/# define CFG_MONITOR_LEN?(256 * 1024) /* Reserve 128k?*/# define CFG_GBL_DATA_SIZE 128?/* Global data size rsvd*/# define CFG_MALLOC_LEN?(CFG_ENV_SIZE + 128*1024)

# define CFG_MONITOR_BASE TEXT_BASE# define CFG_MALLOC_BASE?(CFG_MONITOR_BASE - CFG_MALLOC_LEN)# define CFG_GBL_DATA_OFFSET (CFG_MALLOC_BASE - CFG_GBL_DATA_SIZE)# define CFG_INIT_SP?CFG_GBL_DATA_OFFSET[/b]

--- Quote End ---

I want to know clearly about the Monitor, heap, Global data, stack means and their functions.

And How to set them in nios2 system?

Thank you.

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    20 years ago

    Hi LiangYi,

    The u-boot memory layout for the PK1C20 board is as follows:

    +--------------------+ (Top of SDRAM)

    |

    | u-boot code (256 KB = CFG_MONITOR_LEN)

    |

    +--------------------+ <== CFG_MONITOR_BASE, TEXT_BASE

    |

    | heap (128 KB = CFG_MALLOC_LEN)

    |

    +--------------------+ <== CFG_MALLOC_BASE

    |

    | global data (128 B = CFG_GBL_DATA_SIZE)

    |

    +--------------------+ <== CFG_GLB_DATA_OFFSET, CFG_INIT_SP

    |

    | STACK (Grows down)

    |

    The heap includes room for the ram-based environment (which is dynamically allocated)

    and copied from flash at startup.

    > And How to set them in nios2 system?

    Typically the monitor length is set to some value (2**n) that is larger than the u-boot

    memory footprint. In this case 256 KB ... which is almost twice what is required (depending

    on which features are configured in u-boot).

    The heap can be set to whatever value you like (subject to your actual memory resources). If

    you add your own commands and require a large heap, you can increase this. Many boards

    set this to 128 KB -- a good empirical starting point.

    Set the global data area to 128 -- the global data area is currently less than this ... and is

    very unlikely to change.

    The stack simply grows downward -- so it&#39;s a bad idea to tftpboot or loadb into memory just

    under the u-boot text ;-)

    The macros (which I agree are not the most readable) are set up so the size of the memory

    regions can be easily changed ... without changing the relative layout.

    Regards,

    --Scott