linux-kernel - Re: [PATCH v4 1/2] of: create of

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Message-ID: <CAL_JsqKsF53v7d7uZ3XT4kPFy-2FBWHfvKNSFdTx2oZhmSZkDA@mail.gmail.com>
Date: Mon, 18 Mar 2024 14:26:00 -0500
From: Rob Herring <robh+dt@...nel.org>
To: Guenter Roeck <linux@...ck-us.net>, Stephen Boyd <sboyd@...nel.org>
Cc: Frank Rowand <frowand.list@...il.com>, Clément Léger <clement.leger@...tlin.com>, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Lizhi Hou <lizhi.hou@...inx.com>, Allan Nielsen <allan.nielsen@...rochip.com>, 
	Horatiu Vultur <horatiu.vultur@...rochip.com>, 
	Steen Hegelund <steen.hegelund@...rochip.com>, 
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v4 1/2] of: create of_root if no dtb provided

+Stephen

On Mon, Mar 18, 2024 at 12:09 PM Guenter Roeck <linux@...ck-us.net> wrote:
>
> Hi,
>
> On Fri, Mar 17, 2023 at 12:34:14AM -0500, Frank Rowand wrote:
> > When enabling CONFIG_OF on a platform where of_root is not populated by
> > firmware, we end up without a root node. In order to apply overlays and
> > create subnodes of the root node, we need one. Create this root node
> > by unflattening an empty builtin dtb.
> >
> > If firmware provides a flattened device tree (FDT) then the FDT is
> > unflattened via setup_arch().  Otherwise setup_of(), which is called
> > immediately after setup_arch(), will create the default root node
> > if it does not exist.
> >
> > Signed-off-by: Frank Rowand <frowand.list@...il.com>
>
> This patch results in a crash on nios2.

This patch was never applied. I assume you meant a later version of it
that did get applied.

>
> Building nios2:10m50-ghrd:10m50_defconfig:10m50_devboard.dts ... running ..R failed (crashed)

Booting with DT?

> ------------
> qemu log:
> earlycon: uart8250 at MMIO32 0x18001600 (options '')
> printk: legacy bootconsole [uart8250] enabled
> Linux version 6.8.0-11409-gf6cef5f8c37f (groeck@...ktop) (nios2-linux-gcc (GCC) 11.4.0, GNU ld (GNU Binutils) 2.40) #1 Sun Mar 17 23:38:59 PDT 2024
> Kernel panic - not syncing: early_init_dt_alloc_memory_arch: Failed to allocate 72 bytes align=0x40
> ---[ end Kernel panic - not syncing: early_init_dt_alloc_memory_arch: Failed to allocate 72 bytes align=0x40 ]---

nios2 looks utterly broken to me. This change should be a nop unless
initial_boot_params is NULL. It looks like it is possible for r6 (dtb
address) to be 0 depending on kconfig options, but that would have
skipped copying and unflattening which would then panic in
setup_cpuinfo(). If initial_boot_params is not NULL, then the same
early_init_dt_alloc_memory_arch() calls should fail when copying the
DT. So I don't see how nios2 booting with DT ever worked.

Rob