[BUG] silent hangup when debugging lib/fdtdec.c

[Tom Rini]

On Wed, Nov 26, 2025 at 11:41:14AM +0100, alexander.feilke at ew.tq-group.com wrote:
> On Tuesday, November 25, 2025 17:35 CET, Tom Rini <trini at konsulko.com> wrote:
> 
> > On Tue, Nov 25, 2025 at 05:14:12PM +0100, Alexander Feilke wrote:
> > 
> > > From: Alexander Feilke <alexander.feilke at ew.tq-group.com>
> > > 
> > > Description: U-Boot hangs silently during boot when enabling DEBUG in
> > > lib/fdtdec.c
> > > 
> > > Not sure if its really a bug or rather a configuration issue on my side.
> > > 
> > > Minimal steps to reproduce: <see patch>
> > > 
> > > The hang is caused by `panic("FDT overlap");` later inside the if block.
> > > (see `lib/fdtdec.c:1279` in `fdt_find_separate(void)`)
> > > 
> > > Additionally, no boot log can be seen because serial is initialized after
> > > loading the devicetree in this boot stage (see `common/board_r.c:665` in
> > > `initcall_run_r(void)`)
> > > 
> > > Tested on i.MX6 with configs for tqma6d_mba6 and other tq boards that aren't,
> > > mainlined yet (tqma6ulx_mba6ul and tqma7d_mba7).
> > > 
> > > Any idea what to look for to fix this on our side?
> > > 
> > > Thanks in advance,
> > > Alexander
> > 
> > For very early failures you might need to look at enabling DEBUG_UART
> > which wires in a more direct "just write this to serial port".
> > 
> > -- 
> > Tom
> 
> Thanks for pointing that out. The debug log shows that the global data is
> still located in the SRAM after relocation.
> Printing all variables involved in the panic condition shows, that the stack
> pointer also overflowed, so there appear to be two separate issues.
> 
> if (top > (void *)gd || top > (void *)&stack_ptr) {
> 
> including top, sp and sys_init_sp_addr for completeness:
> 
> <debug_uart>
> FDT 8789d3a0 gd 0091de40
> top 878a7aa8 sp 878543e7
> sys_init_sp_addr 0091ff20
> FDT overlap
> resetting ...
> System reset not supported on this platform
> ### ERROR ### Please RESET the board ###
> 
> 
> Note: I don't use CUSTOM_SYS_INIT_SP_ADDR so the default is used. GENERATED_GBL_DATA_SIZE is 0xe0
> 
> #define SYS_INIT_SP_ADDR	(CFG_SYS_INIT_RAM_ADDR + CFG_SYS_INIT_RAM_SIZE
>  - GENERATED_GBL_DATA_SIZE)
> #define CFG_SYS_INIT_RAM_ADDR	IRAM_BASE_ADDR
> #define CFG_SYS_INIT_RAM_SIZE	IRAM_SIZE
> 
> Do you have any idea how to address these two problems?

Are there similar configs upstream? I know that imx6 is not generally
broken, I boot my mx6cuboxi on current next (and master recently) and
it's not failing like that, for example. Also, adding in one of the imx
custodians..

-- 
Tom
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