Hi Nicolas, On Tue, Jan 18, 2011 at 2:26 PM, Nicolas Pitre <[email protected]> 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 <[email protected]> >> --- >> 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. _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
