[Buildroot] [Proposal] Build RPi dtbo overlays instead of just copying

[Buildroot] [Proposal] Build RPi dtbo overlays instead of just copying

[Scott Ellis]

Currently RPi dtbo overlays come from the rpi-firmware package and are
just copies of the binaries built upstream.

The source for the dtbos are in the same github.com/raspberrypi/linux
tree that Buildroot is using for the kernel and the main board dtb.

I'm suggesting the overlay dtbos should be in sync with the kernel
and the main dtb we are using and get built at the same time.

The particular problem I want to solve is to allow my modifications 
to overlays or addition of new overlays both via standard kernel patches
get built and installed into the image.

I have a patch for this that I am already using.

I understand this is an RPi specific change to linux.mk, so I'm asking
first whether it is of interest and worthwhile submitting a patch.

It currently looks like this in my tree

diff --git a/linux/Config.in b/linux/Config.in
index f19dce1..7f0cb9d 100644
--- a/linux/Config.in
+++ b/linux/Config.in
@@ -383,6 +383,13 @@ config BR2_LINUX_KERNEL_CUSTOM_DTS_PATH

 endif

+config BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT
+       bool "Build Device Tree Overlays"
+       depends on BR2_LINUX_KERNEL_DTS_SUPPORT
+       help
+         Build in-tree device tree overlays.
+         Currently supports Raspberry Pi kernels.
+
 config BR2_LINUX_KERNEL_INSTALL_TARGET
        bool "Install kernel image to /boot in target"
        depends on !BR2_TARGET_ROOTFS_INITRAMFS
diff --git a/linux/linux.mk b/linux/linux.mk
index 7f4432e..f270e6e 100644
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -309,6 +309,13 @@ define LINUX_INSTALL_DTB
 endef
 endif # BR2_LINUX_KERNEL_APPENDED_DTB
 endif # BR2_LINUX_KERNEL_DTB_IS_SELF_BUILT
+
+ifeq ($(BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT),y)
+define LINUX_INSTALL_DTB_OVERLAYS
+       cp $(KERNEL_ARCH_PATH)/boot/dts/overlays/*.dtbo $(1)
+endef
+endif # BR2_LINUX_KERNEL_DTS_OVERLAYS
+
 endif # BR2_LINUX_KERNEL_DTS_SUPPORT

 ifeq ($(BR2_LINUX_KERNEL_APPENDED_DTB),y)
@@ -350,6 +357,10 @@ define LINUX_BUILD_CMDS
        @if grep -q "CONFIG_MODULES=y" $(@D)/.config; then      \
                $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) modules ;        \
        fi
+       $(if $(BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT),
+               $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) dtbs ;           \
+       )
+
        $(LINUX_BUILD_DTB)
        $(LINUX_APPEND_DTB)
 endef
@@ -373,6 +384,8 @@ ifeq ($(BR2_LINUX_KERNEL_INSTALL_TARGET),y)
 define LINUX_INSTALL_KERNEL_IMAGE_TO_TARGET
        $(call LINUX_INSTALL_IMAGE,$(TARGET_DIR)/boot)
        $(call LINUX_INSTALL_DTB,$(TARGET_DIR)/boot)
+       mkdir -p $(TARGET_DIR)/boot/overlays
+       $(call LINUX_INSTALL_DTB_OVERLAYS,$(TARGET_DIR)/boot/overlays)
 endef
 endif

@@ -390,6 +403,8 @@ endef
 define LINUX_INSTALL_IMAGES_CMDS
        $(call LINUX_INSTALL_IMAGE,$(BINARIES_DIR))
        $(call LINUX_INSTALL_DTB,$(BINARIES_DIR))
+       mkdir -p $(BINARIES_DIR)/rpi-firmware/overlays
+       $(call LINUX_INSTALL_DTB_OVERLAYS,$(BINARIES_DIR)/rpi-firmware/overlays)
 endef

 ifeq ($(BR2_STRIP_strip),y)



And something like this to prevent the rpi-firmware package from clobbering
the dtbos just built


diff --git a/package/rpi-firmware/rpi-firmware.mk b/package/rpi-firmware/rpi-firmware.mk
index f71991e..94ceb3b 100644
--- a/package/rpi-firmware/rpi-firmware.mk
+++ b/package/rpi-firmware/rpi-firmware.mk
@@ -21,6 +21,7 @@ define RPI_FIRMWARE_INSTALL_DTB
 endef
 endif

+ifneq ($(BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT),y)
 ifeq ($(BR2_PACKAGE_RPI_FIRMWARE_INSTALL_DTB_OVERLAYS),y)
 define RPI_FIRMWARE_INSTALL_DTB_OVERLAYS
        for ovldtb in  $(@D)/boot/overlays/*.dtbo; do \
@@ -28,6 +29,7 @@ define RPI_FIRMWARE_INSTALL_DTB_OVERLAYS
        done
 endef
 endif
+endif # BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT

 ifeq ($(BR2_PACKAGE_RPI_FIRMWARE_INSTALL_VCDBG),y)
 define RPI_FIRMWARE_INSTALL_TARGET_CMDS


Probably better would be if the new BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT
and the existing BR2_PACKAGE_RPI_FIRMWARE_DTB_OVERLAYS vars were mutually
exclusive in the configuration. I can fix this.

At any rate, is this worth pursuing?

Best regards,
Scott

[Buildroot] [Proposal] Build RPi dtbo overlays instead of just copying

[Thomas Petazzoni]

Hello,

On Wed, 18 Jan 2017 14:32:46 -0500 (EST), Scott Ellis wrote:
> Currently RPi dtbo overlays come from the rpi-firmware package and are
> just copies of the binaries built upstream.
> 
> The source for the dtbos are in the same github.com/raspberrypi/linux
> tree that Buildroot is using for the kernel and the main board dtb.

Indeed.

> I'm suggesting the overlay dtbos should be in sync with the kernel
> and the main dtb we are using and get built at the same time.
> 
> The particular problem I want to solve is to allow my modifications 
> to overlays or addition of new overlays both via standard kernel patches
> get built and installed into the image.

Makes sense.

> I understand this is an RPi specific change to linux.mk, so I'm asking
> first whether it is of interest and worthwhile submitting a patch.

Indeed the below is too RPi specific in my opinion. If we want to merge
a solution, it has to be more generic, which is difficult to achieve
because there are no overlays in the upstream Linux kernel so there is
nothing that shows what should be the "standard" way of
storing/building overlays.

> +ifeq ($(BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT),y)
> +define LINUX_INSTALL_DTB_OVERLAYS
> +       cp $(KERNEL_ARCH_PATH)/boot/dts/overlays/*.dtbo $(1)

Perhaps the location where the .dtbo are produced should be
configurable, since it's not a standardized behavior that they end up
in arch/ARCH/boot/dts/overlays/ ?

>  ifeq ($(BR2_LINUX_KERNEL_APPENDED_DTB),y)
> @@ -350,6 +357,10 @@ define LINUX_BUILD_CMDS
>         @if grep -q "CONFIG_MODULES=y" $(@D)/.config; then      \
>                 $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) modules ;        \
>         fi
> +       $(if $(BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT),
> +               $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) dtbs ;           \
> +       )

I'm not sure how to handle that one. It doesn't relate only to overlay
support, but also to regular Device Trees. It is actually going to
build all Device Trees that are enabled for the currently selected
kernel configuration.

BTW, if there is a make rule for .dtbo, have you tried simply adding
your list of .dtbo of interest to BR2_LINUX_KERNEL_USE_INTREE_DTS ?

> @@ -390,6 +403,8 @@ endef
>  define LINUX_INSTALL_IMAGES_CMDS
>         $(call LINUX_INSTALL_IMAGE,$(BINARIES_DIR))
>         $(call LINUX_INSTALL_DTB,$(BINARIES_DIR))
> +       mkdir -p $(BINARIES_DIR)/rpi-firmware/overlays
> +       $(call LINUX_INSTALL_DTB_OVERLAYS,$(BINARIES_DIR)/rpi-firmware/overlays)

This rpi-firmware reference is clearly too RPi specific to be in
linux.mk.

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

[Buildroot] [Proposal] Build RPi dtbo overlays instead of just copying

[Scott Ellis]

> BTW, if there is a make rule for .dtbo, have you tried simply adding
> your list of .dtbo of interest to BR2_LINUX_KERNEL_USE_INTREE_DTS ?
>

Its a little awkward, but I think it will work.

I had to add the 'overlays/' path to the dts name for the kernel
build to see it

For example

  BR2_LINUX_KERNEL_INTREE_DTS_NAME="bcm2710-rpi-3-b overlays/pwm-with-clk-overlay"

This is the same thing you have to do manually if you don't use the
'make dtbs' target.

scott at fractal:~/rpi/linux$ make pwm-with-clk.dtbo
make: *** No rule to make target 'pwm-with-clk.dtbo'.  Stop.

scott at fractal:~/rpi/linux$ make pwm-with-clk-overlay.dtbo
make: *** No rule to make target 'pwm-with-clk-overlay.dtbo'.  Stop.

scott at fractal:~/rpi/linux$ make overlays/pwm-with-clk.dtbo
make: *** No rule to make target 'overlays/pwm-with-clk.dtbo'.  Stop.

scott at fractal:~/rpi/linux$ make overlays/pwm-with-clk-overlay.dtbo
make: *** No rule to make target 'overlays/pwm-with-clk-overlay.dtbo'.  Stop.

scott at fractal:~/rpi/linux$ make overlays/pwm-with-clk-overlay.dtb
...
DTC     arch/arm/boot/dts/overlays/pwm-with-clk-overlay.dtb


The overlay that's generated has the name 'pwm-with-clk-overlay.dtb'

So it still has to be renamed for the RPi to use it as an overlay

  pwm-with-clk-overlay.dtb -> pwm-with-clk.dtbo

And it has to be copied to the boot partition 'overlays/' directory.

But this can all be handled in a post-xxx script.

Unless there is a better suggestion, I'll play around with doing
it this way instead.

Thanks.

Best regards,
Scott

"Thomas Petazzoni" <thomas.petazzoni@free-electrons.com> said:

> Hello,
> 
> On Wed, 18 Jan 2017 14:32:46 -0500 (EST), Scott Ellis wrote:
>> Currently RPi dtbo overlays come from the rpi-firmware package and are
>> just copies of the binaries built upstream.
>>
>> The source for the dtbos are in the same github.com/raspberrypi/linux
>> tree that Buildroot is using for the kernel and the main board dtb.
> 
> Indeed.
> 
>> I'm suggesting the overlay dtbos should be in sync with the kernel
>> and the main dtb we are using and get built at the same time.
>>
>> The particular problem I want to solve is to allow my modifications
>> to overlays or addition of new overlays both via standard kernel patches
>> get built and installed into the image.
> 
> Makes sense.
> 
>> I understand this is an RPi specific change to linux.mk, so I'm asking
>> first whether it is of interest and worthwhile submitting a patch.
> 
> Indeed the below is too RPi specific in my opinion. If we want to merge
> a solution, it has to be more generic, which is difficult to achieve
> because there are no overlays in the upstream Linux kernel so there is
> nothing that shows what should be the "standard" way of
> storing/building overlays.
> 
>> +ifeq ($(BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT),y)
>> +define LINUX_INSTALL_DTB_OVERLAYS
>> +       cp $(KERNEL_ARCH_PATH)/boot/dts/overlays/*.dtbo $(1)
> 
> Perhaps the location where the .dtbo are produced should be
> configurable, since it's not a standardized behavior that they end up
> in arch/ARCH/boot/dts/overlays/ ?
> 
>>  ifeq ($(BR2_LINUX_KERNEL_APPENDED_DTB),y)
>> @@ -350,6 +357,10 @@ define LINUX_BUILD_CMDS
>>         @if grep -q "CONFIG_MODULES=y" $(@D)/.config; then      \
>>                 $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) modules ; 
>>       \
>>         fi
>> +       $(if $(BR2_LINUX_KERNEL_DTS_OVERLAYS_SUPPORT),
>> +               $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) dtbs ;    
>>       \
>> +       )
> 
> I'm not sure how to handle that one. It doesn't relate only to overlay
> support, but also to regular Device Trees. It is actually going to
> build all Device Trees that are enabled for the currently selected
> kernel configuration.
> 
> BTW, if there is a make rule for .dtbo, have you tried simply adding
> your list of .dtbo of interest to BR2_LINUX_KERNEL_USE_INTREE_DTS ?
>
>> @@ -390,6 +403,8 @@ endef
>>  define LINUX_INSTALL_IMAGES_CMDS
>>         $(call LINUX_INSTALL_IMAGE,$(BINARIES_DIR))
>>         $(call LINUX_INSTALL_DTB,$(BINARIES_DIR))
>> +       mkdir -p $(BINARIES_DIR)/rpi-firmware/overlays
>> +       $(call LINUX_INSTALL_DTB_OVERLAYS,$(BINARIES_DIR)/rpi-firmware/overlays)
> 
> This rpi-firmware reference is clearly too RPi specific to be in
> linux.mk.
> 
> Thomas
> --
> Thomas Petazzoni, CTO, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com
>