[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[James Balean]

Similaly to Linux, this patch adds the ability to copy in and build
out-of-source device tree sources during a U-Boot build.

Signed-off-by: James Balean <james@balean.com.au>
---
 boot/uboot/Config.in | 7 +++++++
 boot/uboot/uboot.mk  | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/boot/uboot/Config.in b/boot/uboot/Config.in
index c33861b..b60541e 100644
--- a/boot/uboot/Config.in
+++ b/boot/uboot/Config.in
@@ -407,4 +407,11 @@ config BR2_TARGET_UBOOT_ENVIMAGE_REDUNDANT
 
 endif # BR2_TARGET_UBOOT_ENVIMAGE
 
+config BR2_TARGET_UBOOT_CUSTOM_DTS_PATH
+	string "Device Tree Source file paths"
+	help
+		Path to the device tree source files. You can
+		provide a list of dts paths to copy,
+		separated by spaces.
+
 endif # BR2_TARGET_UBOOT
diff --git a/boot/uboot/uboot.mk b/boot/uboot/uboot.mk
index 1e22eaa..6104b7d 100644
--- a/boot/uboot/uboot.mk
+++ b/boot/uboot/uboot.mk
@@ -195,6 +195,9 @@ endef
 endif # BR2_TARGET_UBOOT_BUILD_SYSTEM_LEGACY
 
 define UBOOT_BUILD_CMDS
+	$(if $(BR2_TARGET_UBOOT_CUSTOM_DTS_PATH),
+		cp -f $(call qstrip,$(BR2_TARGET_UBOOT_CUSTOM_DTS_PATH)) $(@D)/arch/$(UBOOT_ARCH)/dts/
+	)
 	$(TARGET_CONFIGURE_OPTS) 	\
 		$(MAKE) -C $(@D) $(UBOOT_MAKE_OPTS) 		\
 		$(UBOOT_MAKE_TARGET)
-- 
2.7.4

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[Arnout Vandecappelle]

On 27-03-17 08:12, James Balean wrote:
> Similaly to Linux, this patch adds the ability to copy in and build
> out-of-source device tree sources during a U-Boot build.
> 
> Signed-off-by: James Balean <james@balean.com.au>
> ---
>  boot/uboot/Config.in | 7 +++++++
>  boot/uboot/uboot.mk  | 3 +++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/boot/uboot/Config.in b/boot/uboot/Config.in
> index c33861b..b60541e 100644
> --- a/boot/uboot/Config.in
> +++ b/boot/uboot/Config.in
> @@ -407,4 +407,11 @@ config BR2_TARGET_UBOOT_ENVIMAGE_REDUNDANT
>  
>  endif # BR2_TARGET_UBOOT_ENVIMAGE
>  
> +config BR2_TARGET_UBOOT_CUSTOM_DTS_PATH
> +	string "Device Tree Source file paths"

 Would it make sense to add
	default BR2_LINUX_KERNEL_CUSTOM_DTS_PATH if BR2_LINUX_KERNEL_USE_CUSTOM_DTS
?

 Perhaps also
	depends on BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG
(AFAIK it's not possible to link in a DTB in the legacy build system.)

> +	help
> +		Path to the device tree source files. You can
> +		provide a list of dts paths to copy,
> +		separated by spaces.

 Indentation should be 1 tab + 2 spaces, and wrap at 72 columns (where tab
counts as 8, so 62 significant characters).

 Perhaps you can add

	  To use this device tree source file, the U-Boot configuration
	  file must refer to it.


 Regards,
 Arnout

> +
>  endif # BR2_TARGET_UBOOT
> diff --git a/boot/uboot/uboot.mk b/boot/uboot/uboot.mk
> index 1e22eaa..6104b7d 100644
> --- a/boot/uboot/uboot.mk
> +++ b/boot/uboot/uboot.mk
> @@ -195,6 +195,9 @@ endef
>  endif # BR2_TARGET_UBOOT_BUILD_SYSTEM_LEGACY
>  
>  define UBOOT_BUILD_CMDS
> +	$(if $(BR2_TARGET_UBOOT_CUSTOM_DTS_PATH),
> +		cp -f $(call qstrip,$(BR2_TARGET_UBOOT_CUSTOM_DTS_PATH)) $(@D)/arch/$(UBOOT_ARCH)/dts/
> +	)
>  	$(TARGET_CONFIGURE_OPTS) 	\
>  		$(MAKE) -C $(@D) $(UBOOT_MAKE_OPTS) 		\
>  		$(UBOOT_MAKE_TARGET)
> 

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[James Balean]

Hi Arnout,

Thank you for your reviewing this patch and for your response.

On 27 March 2017 at 23:12, Arnout Vandecappelle <arnout@mind.be> wrote:
>  Would it make sense to add
>         default BR2_LINUX_KERNEL_CUSTOM_DTS_PATH if BR2_LINUX_KERNEL_USE_CUSTOM_DTS
> ?

>  Perhaps also
>         depends on BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG
> (AFAIK it's not possible to link in a DTB in the legacy build system.)

>  Indentation should be 1 tab + 2 spaces, and wrap at 72 columns (where tab
> counts as 8, so 62 significant characters).

>  Perhaps you can add
>
>           To use this device tree source file, the U-Boot configuration
>           file must refer to it.

All very good suggestions, which I will incorporate in a new version of the patch shortly.

Thanks again,
James
-- 
2.7.4

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[James Balean]

Hi Arnout,

On 27 March 2017 at 23:12, Arnout Vandecappelle <arnout@mind.be> wrote:
>  Would it make sense to add
>         default BR2_LINUX_KERNEL_CUSTOM_DTS_PATH if BR2_LINUX_KERNEL_USE_CUSTOM_DTS
> ?

Have reconsidered this suggestion. I think that perhaps it would be best
not to make the U-boot option dependent on the Linux option. As Linux
and U-Boot use two different device tree sources, there may be occasions
when custom DTS configuration must be made to one or the other rather
than both. This is the case with my boards, which have device tree
support in Linux, but not in U-Boot.

Kind regards,
James
-- 
2.7.4

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[Arnout Vandecappelle]

On 28-03-17 08:14, James Balean wrote:
> Hi Arnout,
> 
> On 27 March 2017 at 23:12, Arnout Vandecappelle <arnout@mind.be> wrote:
>>  Would it make sense to add
>>         default BR2_LINUX_KERNEL_CUSTOM_DTS_PATH if BR2_LINUX_KERNEL_USE_CUSTOM_DTS
>> ?
> 
> Have reconsidered this suggestion. I think that perhaps it would be best
> not to make the U-boot option dependent on the Linux option. As Linux
> and U-Boot use two different device tree sources, there may be occasions
> when custom DTS configuration must be made to one or the other rather
> than both. This is the case with my boards, which have device tree
> support in Linux, but not in U-Boot.

 Certainly, but I only suggested to *default* to the same DTS. It is also
possible that the kernel isn't built at all by Buildroot, or that it uses an
in-tree DTS, or that it is built without DTS because the DTB is provided by
U-Boot. All of these cases are covered by the "if
BR2_LINUX_KERNEL_USE_CUSTOM_DTS" part. And even if the both kernel and U-Boot
use a DTS, it is possible to change the default.

 Regards,
 Arnout

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[Thomas Petazzoni]

Hello,

On Tue, 28 Mar 2017 11:01:46 +0200, Arnout Vandecappelle wrote:

> > Have reconsidered this suggestion. I think that perhaps it would be best
> > not to make the U-boot option dependent on the Linux option. As Linux
> > and U-Boot use two different device tree sources, there may be occasions
> > when custom DTS configuration must be made to one or the other rather
> > than both. This is the case with my boards, which have device tree
> > support in Linux, but not in U-Boot.  
> 
>  Certainly, but I only suggested to *default* to the same DTS. It is also
> possible that the kernel isn't built at all by Buildroot, or that it uses an
> in-tree DTS, or that it is built without DTS because the DTB is provided by
> U-Boot. All of these cases are covered by the "if
> BR2_LINUX_KERNEL_USE_CUSTOM_DTS" part. And even if the both kernel and U-Boot
> use a DTS, it is possible to change the default.

I am not entirely convinced that this:

  default BR2_LINUX_KERNEL_CUSTOM_DTS_PATH if BR2_LINUX_KERNEL_USE_CUSTOM_DTS

is really a good idea. IMO, it tries to be too "clever". I'd really
prefer to keep the U-Boot and Linux configurations independent from
each other.



Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[Arnout Vandecappelle]

On 28-03-17 21:53, Thomas Petazzoni wrote:
> Hello,
> 
> On Tue, 28 Mar 2017 11:01:46 +0200, Arnout Vandecappelle wrote:
> 
>>> Have reconsidered this suggestion. I think that perhaps it would be best
>>> not to make the U-boot option dependent on the Linux option. As Linux
>>> and U-Boot use two different device tree sources, there may be occasions
>>> when custom DTS configuration must be made to one or the other rather
>>> than both. This is the case with my boards, which have device tree
>>> support in Linux, but not in U-Boot.  
>>
>>  Certainly, but I only suggested to *default* to the same DTS. It is also
>> possible that the kernel isn't built at all by Buildroot, or that it uses an
>> in-tree DTS, or that it is built without DTS because the DTB is provided by
>> U-Boot. All of these cases are covered by the "if
>> BR2_LINUX_KERNEL_USE_CUSTOM_DTS" part. And even if the both kernel and U-Boot
>> use a DTS, it is possible to change the default.
> 
> I am not entirely convinced that this:
> 
>   default BR2_LINUX_KERNEL_CUSTOM_DTS_PATH if BR2_LINUX_KERNEL_USE_CUSTOM_DTS
> 
> is really a good idea. IMO, it tries to be too "clever". I'd really
> prefer to keep the U-Boot and Linux configurations independent from
> each other.

 Yeah, thinking a bit more about it: if you use the same DT in U-Boot as in the
kernel, then you probably let U-Boot pass it to the kernel so you don't need it
at kernel build time...

 So forget I suggested this :-)

 Regards,
 Arnout

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[Thomas Petazzoni]

Hello,

On Tue, 28 Mar 2017 22:19:02 +0200, Arnout Vandecappelle wrote:

>  Yeah, thinking a bit more about it: if you use the same DT in U-Boot as in the
> kernel, then you probably let U-Boot pass it to the kernel so you don't need it
> at kernel build time...

Not necessarily. The DT can be used by U-Boot itself to know which
peripherals are available, and how they should be configured. I am not
sure there is a U-Boot option to bundle the DT within U-Boot just for
the purpose of passing it to the kernel. But I might be wrong, I
haven't looked in details at how U-Boot uses the DT.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[Arnout Vandecappelle]

On 28-03-17 22:29, Thomas Petazzoni wrote:
> Hello,
> 
> On Tue, 28 Mar 2017 22:19:02 +0200, Arnout Vandecappelle wrote:
> 
>>  Yeah, thinking a bit more about it: if you use the same DT in U-Boot as in the
>> kernel, then you probably let U-Boot pass it to the kernel so you don't need it
>> at kernel build time...
> 
> Not necessarily. The DT can be used by U-Boot itself to know which
> peripherals are available, and how they should be configured.

 But U-Boot can always pass the device tree it uses internally to the kernel, no?


> I am not
> sure there is a U-Boot option to bundle the DT within U-Boot just for
> the purpose of passing it to the kernel.

 I never heard of such an option either.

 Regards,
 Arnout

> But I might be wrong, I
> haven't looked in details at how U-Boot uses the DT.

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[Thomas Petazzoni]

Hello,

On Wed, 29 Mar 2017 00:17:06 +0200, Arnout Vandecappelle wrote:

> > Not necessarily. The DT can be used by U-Boot itself to know which
> > peripherals are available, and how they should be configured.  
> 
>  But U-Boot can always pass the device tree it uses internally to the kernel, no?

I don't know. Would have to check.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[Buildroot] [PATCH] Add out-of-source U-Boot device tree support

[James Balean]

Hi All,

Thank you for your responses. I will submit a new version of the patch
with your suggestions following this.

On 29 March 2017 at 18:09, Thomas Petazzoni
<thomas.petazzoni@free-electrons.com> wrote:
> > > Not necessarily. The DT can be used by U-Boot itself to know which
> > > peripherals are available, and how they should be configured.  
> > 
> >  But U-Boot can always pass the device tree it uses internally to
> >  the kernel, no?
> 
> I don't know. Would have to check.

I believe it is possible to use U-Boot's device tree blob when booting
Linux. U-Boot's DTB is simply concatenated on the end of itself, so the
address at which the blob starts could be determined and supplied to the
'bootm' command when booting Linux. I have not tested this though, so
will report back if I get around to it.

Thanks again,
James

[Buildroot] [PATCH v2] Add out-of-source U-Boot device tree support

[James Balean]

Similaly to Linux, this patch adds the ability to copy in and build
out-of-source device tree sources during a U-Boot build.

Signed-off-by: James Balean <james@balean.com.au>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
Changes for v2:
  - Added dependency on U-Boot Kconfig build system.
  - Code style cleanup

 boot/uboot/Config.in | 14 ++++++++++++++
 boot/uboot/uboot.mk  |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/boot/uboot/Config.in b/boot/uboot/Config.in
index c33861b..ca94749 100644
--- a/boot/uboot/Config.in
+++ b/boot/uboot/Config.in
@@ -407,4 +407,18 @@ config BR2_TARGET_UBOOT_ENVIMAGE_REDUNDANT
 
 endif # BR2_TARGET_UBOOT_ENVIMAGE
 
+if BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG
+
+config BR2_TARGET_UBOOT_CUSTOM_DTS_PATH
+	string "Device Tree Source file paths"
+	help
+	  Path to the device tree source files. You can provide a list
+	  of dts paths to copy, separated by spaces.
+
+	  To use this device tree source file, the U-Boot configuration
+	  file must refer to it.
+
+endif
+
 endif # BR2_TARGET_UBOOT
+
diff --git a/boot/uboot/uboot.mk b/boot/uboot/uboot.mk
index aac692c..1d464d9 100644
--- a/boot/uboot/uboot.mk
+++ b/boot/uboot/uboot.mk
@@ -195,6 +195,9 @@ endef
 endif # BR2_TARGET_UBOOT_BUILD_SYSTEM_LEGACY
 
 define UBOOT_BUILD_CMDS
+	$(if $(BR2_TARGET_UBOOT_CUSTOM_DTS_PATH),
+		cp -f $(call qstrip,$(BR2_TARGET_UBOOT_CUSTOM_DTS_PATH)) $(@D)/arch/$(UBOOT_ARCH)/dts/
+	)
 	$(TARGET_CONFIGURE_OPTS) 	\
 		$(MAKE) -C $(@D) $(UBOOT_MAKE_OPTS) 		\
 		$(UBOOT_MAKE_TARGET)
-- 
2.7.4

[Buildroot] [PATCH v2] Add out-of-source U-Boot device tree support

[Thomas Petazzoni]

Hello,

On Tue,  4 Apr 2017 22:45:51 -0500, James Balean wrote:
> Similaly to Linux, this patch adds the ability to copy in and build
> out-of-source device tree sources during a U-Boot build.
> 
> Signed-off-by: James Balean <james@balean.com.au>
> Cc: Arnout Vandecappelle <arnout@mind.be>
> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> ---
> Changes for v2:
>   - Added dependency on U-Boot Kconfig build system.
>   - Code style cleanup

Applied to master after slightly tweaking the help text and dropping a
needlessly added newline at the end of Config.in.

Thanks!

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com