[PATCH 1/8] arm/dt: Make __vet_atags also accept a dtb image
Grant Likely
grant.likely at secretlab.ca
Wed Jan 19 08:42:52 EST 2011
Hi Nicolas,
On Tue, Jan 18, 2011 at 2:26 PM, Nicolas Pitre <nicolas.pitre at linaro.org> wrote:
> On Tue, 18 Jan 2011, Grant Likely wrote:
>
>> The dtb is passed to the kernel via register r2, which is the same
>> method that is used to pass an atags pointer. This patch modifies
>> __vet_atags to not clear r2 when it encounters a dtb image.
>>
>> Signed-off-by: Grant Likely <grant.likely at secretlab.ca>
>> ---
>> arch/arm/kernel/head-common.S | 19 +++++++++++++------
>> arch/arm/kernel/head.S | 8 ++++----
>> 2 files changed, 17 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
>> index 8f57515..d9a9105 100644
>> --- a/arch/arm/kernel/head-common.S
>> +++ b/arch/arm/kernel/head-common.S
>> @@ -14,6 +14,7 @@
>> #define ATAG_CORE 0x54410001
>> #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
>> #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
>> +#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
>
> ARM can be big endian too. Would be nice to make this endian
> independent, or at least list this limitation in the commit log.
How about:
#ifdef CONFIG_CPU_BIG_ENDIAN
#define OF_DT_MAGIC 0xd00dfeed
#else
#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
#endif
Or is there a better way for loading and comparing big endian values in ARM?
>
>> /*
>> * Exception handling. Something went wrong and we can't proceed. We
>> @@ -105,22 +106,28 @@ __lookup_machine_type_data:
>>
>> /* Determine validity of the r2 atags pointer. The heuristic requires
>> * that the pointer be aligned, in the first 16k of physical RAM and
>> - * that the ATAG_CORE marker is first and present. Future revisions
>> + * that the ATAG_CORE marker is first and present. If CONFIG_OF_FLATTREE
>> + * is selected, then it will also accept a dtb pointer. Future revisions
>> * of this function may be more lenient with the physical address and
>> * may also be able to move the ATAGS block if necessary.
>> *
>> * r8 = machinfo
>> *
>> * Returns:
>> - * r2 either valid atags pointer, or zero
>> + * r2 either valid atags pointer, valid dtb pointer, or zero
>> * r5, r6 corrupted
>> */
>> __vet_atags:
>> tst r2, #0x3 @ aligned?
>> bne 1f
>>
>> - ldr r5, [r2, #0] @ is first tag ATAG_CORE?
>> - cmp r5, #ATAG_CORE_SIZE
>> +#ifdef CONFIG_OF_FLATTREE
>> + ldr r5, [r2, #0] @ is it a DTB?
>> + ldr r6, =OF_DT_MAGIC
>> + cmp r5, r6
>> + beq 2f
>> +#endif
>> + cmp r5, #ATAG_CORE_SIZE @ is first tag ATAG_CORE?
>
> The "ldr r5 ..." is now done only within #ifdef CONFIG_OF_FLATTREE. So
> if CONFIG_OF_FLATTREE is undefined then r5 will contain garbage.
Oops, that was a silly oversight. Fixed now.
g.
>
>
> Nicolas
>
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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