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Documentation: arm: Update for DT-only platforms

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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>
This commit is contained in:
Gregory Fong 2015-02-03 18:49:26 -08:00 committed by Jonathan Corbet
parent c517d838eb
commit dce12391d7
2 changed files with 18 additions and 6 deletions
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9
Documentation/arm/Booting
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@ -58,13 +58,18 @@ serial format options as described in
--------------------------
Existing boot loaders: OPTIONAL
New boot loaders: MANDATORY
New boot loaders: MANDATORY except for DT-only platforms
The boot loader should detect the machine type its running on by some
method. Whether this is a hard coded value or some algorithm that
looks at the connected hardware is beyond the scope of this document.
The boot loader must ultimately be able to provide a MACH_TYPE_xxx
value to the kernel. (see linux/arch/arm/tools/mach-types).
value to the kernel. (see linux/arch/arm/tools/mach-types). This
should be passed to the kernel in register r1.
For DT-only platforms, the machine type will be determined by device
tree. set the machine type to all ones (~0). This is not strictly
necessary, but assures that it will not match any existing types.
4. Setup boot data
------------------

15
Documentation/arm/README
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@ -185,13 +185,20 @@ Kernel entry (head.S)
board devices are used, or the device is setup, and provides that
machine specific "personality."
This fine-grained machine specific selection is controlled by the machine
type ID, which acts both as a run-time and a compile-time code selection
method.
For platforms that support device tree (DT), the machine selection is
controlled at runtime by passing the device tree blob to the kernel. At
compile-time, support for the machine type must be selected. This allows for
a single multiplatform kernel build to be used for several machine types.
You can register a new machine via the web site at:
For platforms that do not use device tree, this machine selection is
controlled by the machine type ID, which acts both as a run-time and a
compile-time code selection method. You can register a new machine via the
web site at:
<http://www.arm.linux.org.uk/developer/machines/>
Note: Please do not register a machine type for DT-only platforms. If your
platform is DT-only, you do not need a registered machine type.
---
Russell King (15/03/2004)