130 lines
3.5 KiB
Text
130 lines
3.5 KiB
Text
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Kernel initialisation parameters on ARM Linux
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---------------------------------------------
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The following document describes the kernel initialisation parameter
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structure, otherwise known as 'struct param_struct' which is used
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for most ARM Linux architectures.
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This structure is used to pass initialisation parameters from the
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kernel loader to the Linux kernel proper, and may be short lived
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through the kernel initialisation process. As a general rule, it
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should not be referenced outside of arch/arm/kernel/setup.c:setup_arch().
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There are a lot of parameters listed in there, and they are described
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below:
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page_size
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This parameter must be set to the page size of the machine, and
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will be checked by the kernel.
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nr_pages
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This is the total number of pages of memory in the system. If
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the memory is banked, then this should contain the total number
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of pages in the system.
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If the system contains separate VRAM, this value should not
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include this information.
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ramdisk_size
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This is now obsolete, and should not be used.
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flags
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Various kernel flags, including:
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bit 0 - 1 = mount root read only
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bit 1 - unused
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bit 2 - 0 = load ramdisk
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bit 3 - 0 = prompt for ramdisk
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rootdev
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major/minor number pair of device to mount as the root filesystem.
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video_num_cols
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video_num_rows
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These two together describe the character size of the dummy console,
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or VGA console character size. They should not be used for any other
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purpose.
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It's generally a good idea to set these to be either standard VGA, or
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the equivalent character size of your fbcon display. This then allows
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all the bootup messages to be displayed correctly.
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video_x
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video_y
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This describes the character position of cursor on VGA console, and
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is otherwise unused. (should not used for other console types, and
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should not be used for other purposes).
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memc_control_reg
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MEMC chip control register for Acorn Archimedes and Acorn A5000
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based machines. May be used differently by different architectures.
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sounddefault
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Default sound setting on Acorn machines. May be used differently by
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different architectures.
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adfsdrives
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Number of ADFS/MFM disks. May be used differently by different
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architectures.
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bytes_per_char_h
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bytes_per_char_v
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These are now obsolete, and should not be used.
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pages_in_bank[4]
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Number of pages in each bank of the systems memory (used for RiscPC).
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This is intended to be used on systems where the physical memory
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is non-contiguous from the processors point of view.
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pages_in_vram
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Number of pages in VRAM (used on Acorn RiscPC). This value may also
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be used by loaders if the size of the video RAM can't be obtained
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from the hardware.
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initrd_start
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initrd_size
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This describes the kernel virtual start address and size of the
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initial ramdisk.
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rd_start
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Start address in sectors of the ramdisk image on a floppy disk.
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system_rev
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system revision number.
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system_serial_low
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system_serial_high
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system 64-bit serial number
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mem_fclk_21285
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The speed of the external oscillator to the 21285 (footbridge),
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which control's the speed of the memory bus, timer & serial port.
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Depending upon the speed of the cpu its value can be between
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0-66 MHz. If no params are passed or a value of zero is passed,
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then a value of 50 Mhz is the default on 21285 architectures.
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paths[8][128]
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These are now obsolete, and should not be used.
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commandline
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Kernel command line parameters. Details can be found elsewhere.
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