Re: [PATCH RFC] env: ti: fdt_high: set no DTB relocation

Tom Rini <[email protected]> Wed, 29 Jul 2026 09:17:19 -0600

Newsgroups	gmane.comp.boot-loaders.u-boot
Message-ID	<20260729151719.GB1773261@bill-the-cat>

On Wed, Jul 29, 2026 at 04:48:55PM +0530, Anshul Dalal wrote:

> From: Hari Nagalla <[email protected]>
> 
> AM62-SIP SK boards have only 512 MB SDRAM. u-boot relocates the kernel
> DTB to upper SDRAM region before starting Linux kernel. This region is
> overlapping with the Firmware IPC carveouts. To avoid the overlap, set
> 'fdt_high' environment variable in u-boot to prevent relocation of DT
> blob.
> 
> without this patch:
> Booting using the fdt blob at 0x88000000
> Working FDT set to 88000000
> Loading Device Tree to 000000009ce49000, end 000000009ce5b8f9 ... OK
> Working FDT set to 9ce49000
> ...
> and subsequently during Linux boot carveout reserve memory fails:
> 
> Starting kernel ...
> ...
> [    0.000000] printk: legacy bootconsole [ns16550a0] enabled
> [    0.000000] efi: UEFI not found.
> [    0.000000] OF: reserved mem: Reserved memory: failed to reserve
> memory for node 'memory@9cc00000': base 0x000000009cc00000, size 14 MiB
> [    0.000000] Reserved memory: created CMA memory pool at
> 0x0000000094600000, size 128 MiB
> 
> with the patch:
>    Booting using the fdt blob at 0x88000000
> Working FDT set to 88000000
>  Using Device Tree in place at 0000000088000000, end 0000000088013375
> Working FDT set to 88000000
> ...
> and subsequent Linux boot
> [    0.000000] efi: UEFI not found.
> [    0.000000] OF: reserved mem: Reserved memory: reserved region for
> node 'memory@9cc00000': base 0x000000009cc00000, size 14 MiB
> 
> Signed-off-by: Hari Nagalla <[email protected]>
> Signed-off-by: Anshul Dalal <[email protected]>
> ---
> During linux boot on AM62x SIP board, U-Boot relocates the fdt to
> reserved-memory regions for IPC. This causes the kernel to fail when
> trying to reserve said memory regions.
> 
> I'm not sure on what's the correct fix here but this RFC addresses the
> problem by disabling relocation to begin with.

The correct fix is to set bootm_size right, among other possibilities.
Please look up some of the older threads where I've explained why
disabling fdt relocation is wrong.

-- 
Tom

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