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microblaze: Fix DTB passing from bootloader

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Little endian system needs to check OF_DT_HEADER
but it is swapped because it is in big-endian.
Microblaze LE provides lwr instruction which loads
magic number in BIG endian format which can be compared.

There is used the fact that if you write 0x1 as word
and load it as byte then you get for big-endian zero
and 1 for little-endian.

Signed-off-by: Michal Simek <monstr@monstr.eu>
This commit is contained in:
Michal Simek 2011-01-26 13:41:05 +01:00
parent 1f0324caef
commit 026a207879
1 changed files with 12 additions and 2 deletions
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14
arch/microblaze/kernel/head.S
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@ -77,8 +77,18 @@ real_start:
We ensure r7 points to a valid FDT, just in case the bootloader
is broken or non-existent */
beqi r7, no_fdt_arg /* NULL pointer? don't copy */
lw r11, r0, r7 /* Does r7 point to a */
rsubi r11, r11, OF_DT_HEADER /* valid FDT? */
/* Does r7 point to a valid FDT? Load HEADER magic number */
/* Run time Big/Little endian platform */
/* Save 1 as word and load byte - 0 - BIG, 1 - LITTLE */
addik r11, r0, 0x1 /* BIG/LITTLE checking value */
/* __bss_start will be zeroed later - it is just temp location */
swi r11, r0, TOPHYS(__bss_start)
lbui r11, r0, TOPHYS(__bss_start)
beqid r11, big_endian /* DO NOT break delay stop dependency */
lw r11, r0, r7 /* Big endian load in delay slot */
lwr r11, r0, r7 /* Little endian load */
big_endian:
rsubi r11, r11, OF_DT_HEADER /* Check FDT header */
beqi r11, _prepare_copy_fdt
or r7, r0, r0 /* clear R7 when not valid DTB */
bnei r11, no_fdt_arg /* No - get out of here */