Re: [PATCH 1/5] of: Add support for linking device tree blobs intovmlinux

[Dirk Brandewie]

On 11/16/2010 06:58 PM, Grant Likely wrote:
> On Tue, Nov 16, 2010 at 7:21 PM, Dirk Brandewie
> <dirk.brandewie@xxxxxxxxx>  wrote:
> > On 11/16/2010 04:39 PM, David Daney wrote:
> > > Thanks for doing this. However I have a few comments...
> > >
> > > On 11/16/2010 02:41 PM, dirk.brandewie@xxxxxxxxx wrote:
> > > > From: Dirk Brandewie<dirk.brandewie@xxxxxxxxx>
> > > >
> > > > /* .data section */
> > > > #define DATA_DATA \
> > > > *(.data) \
> > > > @@ -468,7 +482,8 @@
> > > > MCOUNT_REC() \
> > > > DEV_DISCARD(init.rodata) \
> > > > CPU_DISCARD(init.rodata) \
> > > > - MEM_DISCARD(init.rodata)
> > > > + MEM_DISCARD(init.rodata) \
> > > > + KERNEL_DTB()
> > >
> > > I thought the init.rodata was only for data used by __init things.
> > > Although the
> > > current linker scripts do not put it in the section that gets recycled as
> > > usable
> > > memory.
> > >
> > > IIRC the unflattened version of the device tree has pointers to the
> > > flattened
> > > data. Since the device tree nodes are live for the entire kernel
> > > lifecycle,
> > > shouldn't the device tree blobs be in non-init memory?
> >
> > The contents of the blob get copied to allocated memory during
> > unflatten_device_tree() so the blob that is linked in is no longer needed
> > after init.
>
> Have you written a patch to add this behaviour?  The current code doesn't.  :-)

I misspoke, my blob gets copied to allocated memory during unflatten_device_tree.
my early_init_dt_alloc_memory_arch() returns the physical address of a kmalloc'd
buffer.

You would want copy the dtb that your platform is going to use to non-init memory.

--Dirk

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