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U-Boot has a fairly rigid memory map which is normally not visible unless debugging is enabled in board_f.c Update the 'meminfo' command to show it. This command does not cover arch-specific pieces but gives a good overview of where things are. Signed-off-by: Simon Glass <sjg@chromium.org>
128 lines
4 KiB
ReStructuredText
128 lines
4 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+:
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.. index::
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single: meminfo (command)
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meminfo command
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===============
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Synopsis
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--------
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::
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meminfo
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Description
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-----------
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The meminfo command shows the amount of memory. If ``CONFIG_CMD_MEMINFO_MAP`` is
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enabled, then it also shows the layout of memory used by U-Boot and the region
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which is free for use by images.
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The layout of memory is set up before relocation, within the init sequence in
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``board_init_f()``, specifically the various ``reserve_...()`` functions. This
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'reservation' of memory starts from the top of RAM and proceeds downwards,
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ending with the stack. This results in the maximum possible amount of memory
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being left free for image-loading.
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The meminfo command writes the DRAM size, then the rest of its outputs in 5
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columns:
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Region
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Name of the region
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Base
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Base address of the region, i.e. where it starts in memory
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Size
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Size of the region, which may be a little smaller than the actual size
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reserved, e.g. due to alignment
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End
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End of the region. The last byte of the region is one lower than the address
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shown here
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Gap
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Gap between the end of this region and the base of the one above
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Regions shown are:
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video
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Memory reserved for video framebuffers. This reservation happens in the
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bind() methods of all video drivers which are present before relocation,
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so the size depends on that maximum amount of memory which all such drivers
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want to reserve. This may be significantly greater than the amount actually
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needed, if the display is ultimately set to a smaller resolution or colour
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depth than the maximum supported.
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code
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U-Boot's code and Block-Starting Symbol (BSS) region. Before relocation,
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U-Boot copies its code to a high region and sets up a BSS immediately after
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that. The size of this region is generally therefore ``__bss_end`` -
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``__image_copy_start``
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malloc
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Contains the malloc() heap. The size of this is set by
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``CONFIG_SYS_MALLOC_LEN``.
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board_info
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Contains the ``bd_info`` structure, with some information about the current
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board.
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global_data
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Contains the global-data structure, pointed to by ``gd``. This includes
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various pointers, values and flags which control U-Boot.
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devicetree
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Contains the flatted devicetree blob (FDT) being used by U-Boot to configure
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itself and its devices.
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bootstage
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Contains the bootstage records, which keep track of boot time as U-Boot
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executes. The size of this is determined by
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``CONFIG_BOOTSTAGE_RECORD_COUNT``, with each record taking approximately
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32 bytes.
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bloblist
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Contains the bloblist, which is a list of tables and other data created by
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U-Boot while executed. The size of this is determined by
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``CONFIG_BLOBLIST_SIZE``.
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stack
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Contains U-Boot's stack, growing downwards from the top. The nominal size of
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this region is set by ``CONFIG_STACK_SIZE`` but there is no actual limit
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enforced, so the stack can grow behind that. Images should be loaded lower
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in memory to avoid any conflict.
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free
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Free memory, which is available for loading images. The base address of
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this is ``gd->ram_base`` which is generally set by ``CFG_SYS_SDRAM_BASE``.
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Example
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-------
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This example shows output with both ``CONFIG_CMD_MEMINFO`` and
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``CONFIG_CMD_MEMINFO_MAP`` enabled::
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=> meminfo
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DRAM: 256 MiB
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Region Base Size End Gap
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------------------------------------------------
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video f000000 1000000 10000000
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code ec3a000 3c5d28 efffd28 2d8
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malloc 8c38000 6002000 ec3a000 0
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board_info 8c37f90 68 8c37ff8 8
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global_data 8c37d80 208 8c37f88 8
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devicetree 8c33000 4d7d 8c37d7d 3
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bootstage 8c32c20 3c8 8c32fe8 18
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bloblist 8c32000 400 8c32400 820
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stack 7c31ff0 1000000 8c31ff0 10
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free 0 7c31ff0 7c31ff0 0
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Return value
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------------
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The return value $? is always 0 (true).
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