Re: [PATCH v4 1/2] of: create of_root if no dtb provided

From: Rob Herring <robh+dt@kernel.org>
To: Guenter Roeck <linux@roeck-us.net>, Stephen Boyd <sboyd@kernel.org>
Cc: "Frank Rowand" <frowand.list@gmail.com>,
	"Clément Léger" <clement.leger@bootlin.com>,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Lizhi Hou" <lizhi.hou@xilinx.com>,
	"Allan Nielsen" <allan.nielsen@microchip.com>,
	"Horatiu Vultur" <horatiu.vultur@microchip.com>,
	"Steen Hegelund" <steen.hegelund@microchip.com>,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH v4 1/2] of: create of_root if no dtb provided
Date: Mon, 18 Mar 2024 14:26:00 -0500	[thread overview]
Message-ID: <CAL_JsqKsF53v7d7uZ3XT4kPFy-2FBWHfvKNSFdTx2oZhmSZkDA@mail.gmail.com> (raw)
In-Reply-To: <886049ed-4f5f-4e17-86f4-1245024ade3a@roeck-us.net>

+Stephen

On Mon, Mar 18, 2024 at 12:09 PM Guenter Roeck <linux@roeck-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@gmail.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@desktop) (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