Documentation: arm: Update for DT-only platforms
The documentation specified that a machine type is mandatory and made that assumption in a few places. However, for DT-only platforms, the current advice is that no machine type should be registered, so update accordingly. Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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@ -58,13 +58,18 @@ serial format options as described in
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--------------------------
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Existing boot loaders: OPTIONAL
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New boot loaders: MANDATORY
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New boot loaders: MANDATORY except for DT-only platforms
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The boot loader should detect the machine type its running on by some
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method. Whether this is a hard coded value or some algorithm that
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looks at the connected hardware is beyond the scope of this document.
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The boot loader must ultimately be able to provide a MACH_TYPE_xxx
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value to the kernel. (see linux/arch/arm/tools/mach-types).
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value to the kernel. (see linux/arch/arm/tools/mach-types). This
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should be passed to the kernel in register r1.
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For DT-only platforms, the machine type will be determined by device
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tree. set the machine type to all ones (~0). This is not strictly
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necessary, but assures that it will not match any existing types.
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4. Setup boot data
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------------------
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@ -185,13 +185,20 @@ Kernel entry (head.S)
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board devices are used, or the device is setup, and provides that
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machine specific "personality."
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This fine-grained machine specific selection is controlled by the machine
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type ID, which acts both as a run-time and a compile-time code selection
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method.
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For platforms that support device tree (DT), the machine selection is
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controlled at runtime by passing the device tree blob to the kernel. At
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compile-time, support for the machine type must be selected. This allows for
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a single multiplatform kernel build to be used for several machine types.
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You can register a new machine via the web site at:
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For platforms that do not use device tree, this machine selection is
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controlled by the machine type ID, which acts both as a run-time and a
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compile-time code selection method. You can register a new machine via the
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web site at:
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<http://www.arm.linux.org.uk/developer/machines/>
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Note: Please do not register a machine type for DT-only platforms. If your
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platform is DT-only, you do not need a registered machine type.
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---
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Russell King (15/03/2004)
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