[PATCH] fdt: Allow OF_HAS_PRIOR_STAGE to be disabled in defconfig

[PATCH] fdt: Allow OF_HAS_PRIOR_STAGE to be disabled in defconfig

[Simon Glass]

At present it is impossible to change the qemu_arm64 defconfig to
obtain a devicetree from the U-Boot build.

This is necessary for FIT validation, for example, where the signature
node must be compiled into U-Boot.

A proposed change to QEMU has been blocked for several years. As a
workaround, the only option is to use QEMU's dumpdtb option, merge in
the signature node manually and then disable OF_HAS_PRIOR_STAGE

Unfortunately the only way to disable OF_HAS_PRIOR_STAGE at present is
to hack the Kconfig. So update it to allow use from defconfig. This
avoids needing to patch U-Boot to get this working.

Signed-off-by: Simon Glass <sjg@chromium.org>
Link: https://patchwork.kernel.org/project/qemu-devel/patch/20210926183410.256484-1-sjg@chromium.org/#24481799
---

 dts/Kconfig | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/dts/Kconfig b/dts/Kconfig
index 2e88d210bb8..2fe4468d1a9 100644
--- a/dts/Kconfig
+++ b/dts/Kconfig
@@ -190,7 +190,7 @@ config OF_BOARD
 	  earlier stage should enable OF_HAS_PRIOR_STAGE.
 
 config OF_HAS_PRIOR_STAGE
-	bool
+	bool "Device tree comes from prior-stage firmware"
 	help
 	  Indicates that a prior stage of the firmware (before U-Boot proper)
 	  makes use of device tree and this board normally boots with that prior
@@ -205,8 +205,13 @@ config OF_HAS_PRIOR_STAGE
 	  development purposes, but it is not recommended, and likely will not
 	  even work, for production systems.
 
-	  Note: This option must be set in Kconfig and cannot be enabled or
-	  disabled in the board's defconfig file.
+	  Note: This option can be updated in the board's defconfig file if
+	  needed. E.g. for QEMU to support FIT validation the devicetree must
+	  include a public key.
+
+	  See also this for context:
+
+	  https://patchwork.kernel.org/project/qemu-devel/patch/20210926183410.256484-1-sjg@chromium.org/#24481799
 
 config OF_OMIT_DTB
 	bool "Omit the device tree output when building"
-- 
2.43.0

Re: [PATCH] fdt: Allow OF_HAS_PRIOR_STAGE to be disabled in defconfig

[Tom Rini]

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On Fri, Apr 04, 2025 at 06:53:49AM +1300, Simon Glass wrote:

> At present it is impossible to change the qemu_arm64 defconfig to
> obtain a devicetree from the U-Boot build.
> 
> This is necessary for FIT validation, for example, where the signature
> node must be compiled into U-Boot.
> 
> A proposed change to QEMU has been blocked for several years. As a
> workaround, the only option is to use QEMU's dumpdtb option, merge in
> the signature node manually and then disable OF_HAS_PRIOR_STAGE
> 
> Unfortunately the only way to disable OF_HAS_PRIOR_STAGE at present is
> to hack the Kconfig. So update it to allow use from defconfig. This
> avoids needing to patch U-Boot to get this working.
> 
> Signed-off-by: Simon Glass <sjg@chromium.org>
> Link: https://patchwork.kernel.org/project/qemu-devel/patch/20210926183410.256484-1-sjg@chromium.org/#24481799

How about instead we do something like:
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b7311d3b754b..44e45a304cd0 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1080,7 +1080,7 @@ config ARCH_QEMU
 	imply DM_RNG
 	imply DM_RTC
 	imply RTC_PL031
-	imply OF_HAS_PRIOR_STAGE if !TARGET_QEMU_ARM_SBSA
+	imply OF_HAS_PRIOR_STAGE if !QEMU_MANUAL_DTB
 	imply VIDEO
 	imply VIDEO_BOCHS
 	imply SYS_WHITE_ON_BLACK
diff --git a/board/emulation/common/Kconfig b/board/emulation/common/Kconfig
index 4c15c8bcb891..9053f2ff2f55 100644
--- a/board/emulation/common/Kconfig
+++ b/board/emulation/common/Kconfig
@@ -13,3 +13,10 @@ config MTDPARTS_NOR1
 	help
 	  This define the partition of nor1 used to build mtparts dynamically
 	  for the u-boot env stored on nor1.
+
+config QEMU_MANUAL_DTB
+	bool "Manually provide a device tree to QEMU"
+	depends on ARCH_QEMU # Expand more if needed
+	help
+	  For some use cases, such as FIT validation of U-Boot itself we need
+	  to override the device tree that QEMU would normally provide to us.

This way we don't start opening asking OF_HAS_PRIOR_STAGE.

-- 
Tom

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Re: [PATCH] fdt: Allow OF_HAS_PRIOR_STAGE to be disabled in defconfig

[Simon Glass]

Hi Tom,

On Fri, 4 Apr 2025 at 08:02, Tom Rini <trini@konsulko.com> wrote:
>
> On Fri, Apr 04, 2025 at 06:53:49AM +1300, Simon Glass wrote:
>
> > At present it is impossible to change the qemu_arm64 defconfig to
> > obtain a devicetree from the U-Boot build.
> >
> > This is necessary for FIT validation, for example, where the signature
> > node must be compiled into U-Boot.
> >
> > A proposed change to QEMU has been blocked for several years. As a
> > workaround, the only option is to use QEMU's dumpdtb option, merge in
> > the signature node manually and then disable OF_HAS_PRIOR_STAGE
> >
> > Unfortunately the only way to disable OF_HAS_PRIOR_STAGE at present is
> > to hack the Kconfig. So update it to allow use from defconfig. This
> > avoids needing to patch U-Boot to get this working.
> >
> > Signed-off-by: Simon Glass <sjg@chromium.org>
> > Link: https://patchwork.kernel.org/project/qemu-devel/patch/20210926183410.256484-1-sjg@chromium.org/#24481799
>
> How about instead we do something like:
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index b7311d3b754b..44e45a304cd0 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1080,7 +1080,7 @@ config ARCH_QEMU
>         imply DM_RNG
>         imply DM_RTC
>         imply RTC_PL031
> -       imply OF_HAS_PRIOR_STAGE if !TARGET_QEMU_ARM_SBSA
> +       imply OF_HAS_PRIOR_STAGE if !QEMU_MANUAL_DTB
>         imply VIDEO
>         imply VIDEO_BOCHS
>         imply SYS_WHITE_ON_BLACK
> diff --git a/board/emulation/common/Kconfig b/board/emulation/common/Kconfig
> index 4c15c8bcb891..9053f2ff2f55 100644
> --- a/board/emulation/common/Kconfig
> +++ b/board/emulation/common/Kconfig
> @@ -13,3 +13,10 @@ config MTDPARTS_NOR1
>         help
>           This define the partition of nor1 used to build mtparts dynamically
>           for the u-boot env stored on nor1.
> +
> +config QEMU_MANUAL_DTB
> +       bool "Manually provide a device tree to QEMU"
> +       depends on ARCH_QEMU # Expand more if needed
> +       help
> +         For some use cases, such as FIT validation of U-Boot itself we need
> +         to override the device tree that QEMU would normally provide to us.
>
> This way we don't start opening asking OF_HAS_PRIOR_STAGE.

Yes that seems fine, thanks. If it ends up becoming a more general
problem we can worry about it then.

Regards,
Simon

Re: [PATCH] fdt: Allow OF_HAS_PRIOR_STAGE to be disabled in defconfig

[Tom Rini]

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On Fri, Apr 04, 2025 at 09:40:18AM +1300, Simon Glass wrote:
> Hi Tom,
> 
> On Fri, 4 Apr 2025 at 08:02, Tom Rini <trini@konsulko.com> wrote:
> >
> > On Fri, Apr 04, 2025 at 06:53:49AM +1300, Simon Glass wrote:
> >
> > > At present it is impossible to change the qemu_arm64 defconfig to
> > > obtain a devicetree from the U-Boot build.
> > >
> > > This is necessary for FIT validation, for example, where the signature
> > > node must be compiled into U-Boot.
> > >
> > > A proposed change to QEMU has been blocked for several years. As a
> > > workaround, the only option is to use QEMU's dumpdtb option, merge in
> > > the signature node manually and then disable OF_HAS_PRIOR_STAGE
> > >
> > > Unfortunately the only way to disable OF_HAS_PRIOR_STAGE at present is
> > > to hack the Kconfig. So update it to allow use from defconfig. This
> > > avoids needing to patch U-Boot to get this working.
> > >
> > > Signed-off-by: Simon Glass <sjg@chromium.org>
> > > Link: https://patchwork.kernel.org/project/qemu-devel/patch/20210926183410.256484-1-sjg@chromium.org/#24481799
> >
> > How about instead we do something like:
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index b7311d3b754b..44e45a304cd0 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -1080,7 +1080,7 @@ config ARCH_QEMU
> >         imply DM_RNG
> >         imply DM_RTC
> >         imply RTC_PL031
> > -       imply OF_HAS_PRIOR_STAGE if !TARGET_QEMU_ARM_SBSA
> > +       imply OF_HAS_PRIOR_STAGE if !QEMU_MANUAL_DTB
> >         imply VIDEO
> >         imply VIDEO_BOCHS
> >         imply SYS_WHITE_ON_BLACK
> > diff --git a/board/emulation/common/Kconfig b/board/emulation/common/Kconfig
> > index 4c15c8bcb891..9053f2ff2f55 100644
> > --- a/board/emulation/common/Kconfig
> > +++ b/board/emulation/common/Kconfig
> > @@ -13,3 +13,10 @@ config MTDPARTS_NOR1
> >         help
> >           This define the partition of nor1 used to build mtparts dynamically
> >           for the u-boot env stored on nor1.
> > +
> > +config QEMU_MANUAL_DTB
> > +       bool "Manually provide a device tree to QEMU"
> > +       depends on ARCH_QEMU # Expand more if needed
> > +       help
> > +         For some use cases, such as FIT validation of U-Boot itself we need
> > +         to override the device tree that QEMU would normally provide to us.
> >
> > This way we don't start opening asking OF_HAS_PRIOR_STAGE.
> 
> Yes that seems fine, thanks. If it ends up becoming a more general
> problem we can worry about it then.

Thanks. I'll let you make that up in to a more general and complete
patch, that was just me poking at the files for a moment.

-- 
Tom

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