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xtensa: add device trees support

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Device trees allow specification of hardware topology and device
parameters at runtime instead of hard-coding them in platform setup
code. This allows running single binary kernel on a range of compatible
boards.

New boot parameters tag BP_TAG_FDT is allocated and a pointer to flat
device tree is passed in it.

Note that current interrupt mapping scheme uses single cell for
interrupt identification. That means that IRQ numbers used in DTS must
be CPU internal IRQ numbers, not external. It is possible to extend
interrupt identification to two cells, and use second cell to tell
external IRQ numbers form internal. That would allow to use single DTS
on multiple boards with different mapping of external IRQ numbers.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>
This commit is contained in:
Max Filippov
2012-11-04 00:30:13 +04:00
committed by Chris Zankel
parent 2206d5dd9a
commit da844a8177
7 changed files with 166 additions and 27 deletions
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1
arch/xtensa/include/asm/bootparam.h
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@@ -22,6 +22,7 @@
#define BP_TAG_MEMORY 0x1003 /* memory addr and size (bp_meminfo) */
#define BP_TAG_SERIAL_BAUSRATE 0x1004 /* baud rate of current console. */
#define BP_TAG_SERIAL_PORT 0x1005 /* serial device of current console */
#define BP_TAG_FDT 0x1006 /* flat device tree addr */
#define BP_TAG_FIRST 0x7B0B /* first tag with a version number */
#define BP_TAG_LAST 0x7E0B /* last tag */