linux-kernel - Re: [PATCH v3 7/7] of: Add KUnit test to confirm DTB is loaded

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Message-ID: <2185a3cc3152a0b9a94b0c64353bc9a1.sboyd@kernel.org>
Date: Fri, 09 Feb 2024 18:59:33 -0800
From: Stephen Boyd <sboyd@...nel.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: David Gow <davidgow@...gle.com>, Rob Herring <robh+dt@...nel.org>, linux-kernel@...r.kernel.org, patches@...ts.linux.dev, linux-um@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, kunit-dev@...glegroups.com, linux-kselftest@...r.kernel.org, devicetree@...r.kernel.org, Frank Rowand <frowand.list@...il.com>, Brendan Higgins <brendan.higgins@...ux.dev>
Subject: Re: [PATCH v3 7/7] of: Add KUnit test to confirm DTB is loaded

Quoting Geert Uytterhoeven (2024-02-05 11:55:29)
> On Mon, Feb 5, 2024 at 8:19 PM Stephen Boyd <sboyd@...nel.org> wrote:
> > Quoting David Gow (2024-02-02 20:10:17)
> > > On Sat, 3 Feb 2024 at 03:59, Stephen Boyd <sboyd@...nel.org> wrote:
> > > > Add a KUnit test that confirms a DTB has been loaded, i.e. there is a
> > > > root node, and that the of_have_populated_dt() API works properly.
> > > >
> > > > Cc: Rob Herring <robh+dt@...nel.org>
> > > > Cc: Frank Rowand <frowand.list@...il.com>
> > > > Cc: David Gow <davidgow@...gle.com>
> > > > Cc: Brendan Higgins <brendan.higgins@...ux.dev>
> > > > Signed-off-by: Stephen Boyd <sboyd@...nel.org>
> > > > ---
> > >
> > > This looks pretty good to me test-wise, though it still fails on m68k.
> > > (Everything else I tried it on works, though I've definitely not tried
> > > _every_ architecture.)
> > >
> > > aarch64: PASSED
> > > i386: PASSED
> > > x86_64: PASSED
> > > x86_64 KASAN: PASSED
> > > powerpc64: PASSED
> > > UML: PASSED
> > > UML LLVM: PASSED
> > > m68k: FAILED
> > > > $ qemu-system-m68k -nodefaults -m 1024 -kernel .kunit-all-m68k/vmlinux -append 'kunit.enable=1 console=hvc0 kunit_shutdown=reboot' -no-reboot -nographic -serial stdio -machine virt
> > > > [11:55:05] ===================== dtb (2 subtests) =====================
> > > > [11:55:05] # dtb_root_node_found_by_path: EXPECTATION FAILED at drivers/of/of_test.c:18
> > > > [11:55:05] Expected np is not null, but is
> > > > [11:55:05] [FAILED] dtb_root_node_found_by_path
> > > > [11:55:05] # dtb_root_node_populates_of_root: EXPECTATION FAILED at drivers/of/of_test.c:28
> > > > [11:55:05] Expected of_root is not null, but is
> > > > [11:55:05] [FAILED] dtb_root_node_populates_of_root
> > > > [11:55:05]     # module: of_test
> > > > [11:55:05] # dtb: pass:0 fail:2 skip:0 total:2
> > > > [11:55:05] # Totals: pass:0 fail:2 skip:0 total:2
> > > > [11:55:05] ======================= [FAILED] dtb =======================
> >
> > Ah yeah I forgot to mention that. m68k fails because it doesn't call the
> > unflatten_(and_copy)?_device_tree() function, so we don't populate a
> > root node on that architecture. One solution would be to make CONFIG_OF
> > unavailable on m68k. Or we have to make sure DT works on any
> > architecture. Rob, what do you prefer here?
> 
> I guess the latter?
> Alpha, hexagon, parisc, s390, and sparc are also lacking calls
> to unflatten.*device_tree().
> 

sparc does that on purpose. Perhaps it's simplest to call
unflatten_device_tree() if of_root is still NULL after setup_arch()
returns.

---8<---
diff --git a/init/main.c b/init/main.c
index e24b0780fdff..02f5cf8be6c1 100644
--- a/init/main.c
+++ b/init/main.c
@@ -97,6 +97,8 @@
 #include <linux/jump_label.h>
 #include <linux/kcsan.h>
 #include <linux/init_syscalls.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
 #include <linux/stackdepot.h>
 #include <linux/randomize_kstack.h>
 #include <net/net_namespace.h>
@@ -895,6 +897,8 @@ void start_kernel(void)
 	pr_notice("%s", linux_banner);
 	early_security_init();
 	setup_arch(&command_line);
+	if (!of_root)
+		unflatten_device_tree();
 	setup_boot_config();
 	setup_command_line(command_line);
 	setup_nr_cpu_ids();