linux-kernel - Re: [PATCH 6/6] of: Add KUnit test to confirm DTB is loaded

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Message-ID: <47062115ff518edf8c4b02e22f3058bc.sboyd@kernel.org>
Date: Mon, 22 Jan 2024 14:48:03 -0800
From: Stephen Boyd <sboyd@...nel.org>
To: David Gow <davidgow@...gle.com>
Cc: 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 6/6] of: Add KUnit test to confirm DTB is loaded

Quoting David Gow (2024-01-15 21:03:12)
> On Sat, 13 Jan 2024 at 04:07, 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>
> > ---
> 
> I won't pretend to be a devicetree expert, but this looks good to me
> from a KUnit point of view, and passes comfortably here.
> 
> checkpatch seems to have one complaint about the kconfig help text.
> Personally, I think the brief description is fine.
> 
> Reviewed-by: David Gow <davidgow@...gle.com>
> 

Thanks! I noticed that x86 has some devicetree init code. Did you happen
to try on an x86 kvm instance? Or only run on UML?

----8<----
diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
index afd09924094e..650752d112a6 100644
--- a/arch/x86/kernel/devicetree.c
+++ b/arch/x86/kernel/devicetree.c
@@ -283,22 +283,24 @@ void __init x86_flattree_get_config(void)
 	u32 size, map_len;
 	void *dt;
 
-	if (!initial_dtb)
-		return;
+	if (initial_dtb) {
+		map_len = max(PAGE_SIZE - (initial_dtb & ~PAGE_MASK), (u64)128);
 
-	map_len = max(PAGE_SIZE - (initial_dtb & ~PAGE_MASK), (u64)128);
+		dt = early_memremap(initial_dtb, map_len);
+		size = fdt_totalsize(dt);
+		if (map_len < size) {
+			early_memunmap(dt, map_len);
+			dt = early_memremap(initial_dtb, size);
+			map_len = size;
+		}
 
-	dt = early_memremap(initial_dtb, map_len);
-	size = fdt_totalsize(dt);
-	if (map_len < size) {
-		early_memunmap(dt, map_len);
-		dt = early_memremap(initial_dtb, size);
-		map_len = size;
+		early_init_dt_verify(dt);
 	}
 
-	early_init_dt_verify(dt);
 	unflatten_and_copy_device_tree();
-	early_memunmap(dt, map_len);
+
+	if (initial_dtb)
+		early_memunmap(dt, map_len);
 }
 #endif