2020-10-08 07:24:20 -07:00
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.. SPDX-License-Identifier: GPL-2.0
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DeviceTree Booting
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------------------
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There is one single 32bit entry point to the kernel at code32_start,
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the decompressor (the real mode entry point goes to the same 32bit
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entry point once it switched into protected mode). That entry point
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supports one calling convention which is documented in
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2023-03-14 16:06:44 -07:00
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Documentation/arch/x86/boot.rst
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2020-10-08 07:24:20 -07:00
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The physical pointer to the device-tree block is passed via setup_data
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which requires at least boot protocol 2.09.
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The type filed is defined as
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#define SETUP_DTB 2
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This device-tree is used as an extension to the "boot page". As such it
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does not parse / consider data which is already covered by the boot
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page. This includes memory size, reserved ranges, command line arguments
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or initrd address. It simply holds information which can not be retrieved
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otherwise like interrupt routing or a list of devices behind an I2C bus.
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