[PATCH 0/2] arm/arm64: dts: Enable device-tree overlay support for RPi devices

[PATCH 0/2] arm/arm64: dts: Enable device-tree overlay support for RPi devices

[Aurelien Jarno]

This patchset changes the generation of the Raspberry Pi devices DTB
files to improve the support for out-of-tree device-tree overlays, like
it has recently been done for the Nvidia SoCs.

I personally only need that for arm64, but I have added a similar patch
to do the same on arm.

Aurelien Jarno (2):
  arm64: dts: broadcom: Enable device-tree overlay support for RPi
    devices
  arm: dts: Enable device-tree overlay support for RPi devices

 arch/arm/boot/dts/Makefile            | 18 ++++++++++++++++++
 arch/arm64/boot/dts/broadcom/Makefile | 11 +++++++++++
 2 files changed, 29 insertions(+)

-- 
2.34.1

[PATCH 1/2] arm64: dts: broadcom: Enable device-tree overlay support for RPi devices

[Aurelien Jarno]

Add the '-@' DTC option for the Raspberry Pi devices. This option
populates the '__symbols__' node that contains all the necessary symbols
for supporting device-tree overlays (for instance from the firmware or
the bootloader) on these devices.

The Rasbperry Pi devices are well known for their GPIO header, that
allow various "HATs" or other modules do be connected and this enables
users to create out-of-tree device-tree overlays for these modules.

Please note that this change does increase the size of the resulting DTB
by ~40%. For example, with v5.17 increase in size is as follows:

  bcm2711-rpi-400.dtb       26481 -> 36830 bytes
  bcm2711-rpi-4-b.dtb       26537 -> 36886 bytes
  bcm2711-rpi-cm4-io.dtb    26426 -> 36945 bytes
  bcm2837-rpi-3-a-plus.dtb  14133 -> 19740 bytes
  bcm2837-rpi-3-b.dtb       14310 -> 20006 bytes
  bcm2837-rpi-3-b-plus.dtb  14670 -> 20474 bytes
  bcm2837-rpi-cm3-io3.dtb   13680 -> 19266 bytes

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
---
 arch/arm64/boot/dts/broadcom/Makefile | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm64/boot/dts/broadcom/Makefile b/arch/arm64/boot/dts/broadcom/Makefile
index 5082fcd1fea5..0aa8ee2afdd5 100644
--- a/arch/arm64/boot/dts/broadcom/Makefile
+++ b/arch/arm64/boot/dts/broadcom/Makefile
@@ -1,4 +1,15 @@
 # SPDX-License-Identifier: GPL-2.0
+
+# Enables support for device-tree overlays
+DTC_FLAGS_bcm2711-rpi-400 := -@
+DTC_FLAGS_bcm2711-rpi-4-b := -@
+DTC_FLAGS_bcm2711-rpi-cm4-io := -@
+DTC_FLAGS_bcm2837-rpi-3-a-plus := -@
+DTC_FLAGS_bcm2837-rpi-3-b := -@
+DTC_FLAGS_bcm2837-rpi-3-b-plus := -@
+DTC_FLAGS_bcm2837-rpi-cm3-io3 := -@
+DTC_FLAGS_bcm2837-rpi-zero-2-w := -@
+
 dtb-$(CONFIG_ARCH_BCM2835) += bcm2711-rpi-400.dtb \
 			      bcm2711-rpi-4-b.dtb \
 			      bcm2711-rpi-cm4-io.dtb \
-- 
2.34.1

Re: [PATCH 1/2] arm64: dts: broadcom: Enable device-tree overlay support for RPi devices

[Uwe Kleine-König]

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Hello,

[expanded Cc: to include William Zhang and Florian Fainelli]

On Mon, Apr 11, 2022 at 12:59:39AM +0200, Aurelien Jarno wrote:
> Add the '-@' DTC option for the Raspberry Pi devices. This option
> populates the '__symbols__' node that contains all the necessary symbols
> for supporting device-tree overlays (for instance from the firmware or
> the bootloader) on these devices.
> 
> The Rasbperry Pi devices are well known for their GPIO header, that
> allow various "HATs" or other modules do be connected and this enables
> users to create out-of-tree device-tree overlays for these modules.
> 
> Please note that this change does increase the size of the resulting DTB
> by ~40%. For example, with v5.17 increase in size is as follows:
> 
>   bcm2711-rpi-400.dtb       26481 -> 36830 bytes
>   bcm2711-rpi-4-b.dtb       26537 -> 36886 bytes
>   bcm2711-rpi-cm4-io.dtb    26426 -> 36945 bytes
>   bcm2837-rpi-3-a-plus.dtb  14133 -> 19740 bytes
>   bcm2837-rpi-3-b.dtb       14310 -> 20006 bytes
>   bcm2837-rpi-3-b-plus.dtb  14670 -> 20474 bytes
>   bcm2837-rpi-cm3-io3.dtb   13680 -> 19266 bytes
> 
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> ---
>  arch/arm64/boot/dts/broadcom/Makefile | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/broadcom/Makefile b/arch/arm64/boot/dts/broadcom/Makefile
> index 5082fcd1fea5..0aa8ee2afdd5 100644
> --- a/arch/arm64/boot/dts/broadcom/Makefile
> +++ b/arch/arm64/boot/dts/broadcom/Makefile
> @@ -1,4 +1,15 @@
>  # SPDX-License-Identifier: GPL-2.0
> +
> +# Enables support for device-tree overlays
> +DTC_FLAGS_bcm2711-rpi-400 := -@
> +DTC_FLAGS_bcm2711-rpi-4-b := -@
> +DTC_FLAGS_bcm2711-rpi-cm4-io := -@
> +DTC_FLAGS_bcm2837-rpi-3-a-plus := -@
> +DTC_FLAGS_bcm2837-rpi-3-b := -@
> +DTC_FLAGS_bcm2837-rpi-3-b-plus := -@
> +DTC_FLAGS_bcm2837-rpi-cm3-io3 := -@
> +DTC_FLAGS_bcm2837-rpi-zero-2-w := -@

Instead of setting these all explicitly a single

DTC_FLAGS := -@

would work, too, without changing how the dts in subdirs are compiled.
IMHO this would be suiteable for arch/arm64/boot/dts/broadcom.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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[PATCH 2/2] arm: dts: Enable device-tree overlay support for RPi devices

[Aurelien Jarno]

Add the '-@' DTC option for the Raspberry Pi devices. This option
populates the '__symbols__' node that contains all the necessary symbols
for supporting device-tree overlays (for instance from the firmware or
the bootloader) on these devices.

The Rasbperry Pi devices are well known for their GPIO header, that
allow various "HATs" or other modules do be connected and this enables
users to create out-of-tree device-tree overlays for these modules.

Please note that this change does increase the size of the resulting DTB
by ~40%. For example, with v5.17 increase in size is as follows:

  bcm2711-rpi-400.dtb       26481 -> 36830 bytes
  bcm2711-rpi-4-b.dtb       26537 -> 36886 bytes
  bcm2711-rpi-cm4-io.dtb    26426 -> 36945 bytes
  bcm2835-rpi-a.dtb         12641 -> 17852 bytes
  bcm2835-rpi-a-plus.dtb    12765 -> 17976 bytes
  bcm2835-rpi-b.dtb         12763 -> 17998 bytes
  bcm2835-rpi-b-plus.dtb    12979 -> 18263 bytes
  bcm2835-rpi-b-rev2.dtb    12847 -> 18131 bytes
  bcm2835-rpi-cm1-io1.dtb   12839 -> 18113 bytes
  bcm2835-rpi-zero.dtb      12681 -> 17924 bytes
  bcm2835-rpi-zero-w.dtb    13135 -> 18430 bytes
  bcm2836-rpi-2-b.dtb       13687 -> 19255 bytes
  bcm2837-rpi-3-a-plus.dtb  14133 -> 19740 bytes
  bcm2837-rpi-3-b.dtb       14310 -> 20006 bytes
  bcm2837-rpi-3-b-plus.dtb  14670 -> 20474 bytes
  bcm2837-rpi-cm3-io3.dtb   13680 -> 19266 bytes

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
---
 arch/arm/boot/dts/Makefile | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm/boot/dts/Makefile b/arch/arm/boot/dts/Makefile
index 7c16f8a2b738..85644149de44 100644
--- a/arch/arm/boot/dts/Makefile
+++ b/arch/arm/boot/dts/Makefile
@@ -81,6 +81,24 @@ dtb-$(CONFIG_SOC_SAMA7G5) += \
 	at91-sama7g5ek.dtb
 dtb-$(CONFIG_ARCH_AXXIA) += \
 	axm5516-amarillo.dtb
+# Enables support for device-tree overlays
+DTC_FLAGS_bcm2835-rpi-b := -@
+DTC_FLAGS_bcm2835-rpi-a := -@
+DTC_FLAGS_bcm2835-rpi-b-rev2 := -@
+DTC_FLAGS_bcm2835-rpi-b-plus := -@
+DTC_FLAGS_bcm2835-rpi-a-plus := -@
+DTC_FLAGS_bcm2835-rpi-cm1-io1 := -@
+DTC_FLAGS_bcm2836-rpi-2-b := -@
+DTC_FLAGS_bcm2837-rpi-3-a-plus := -@
+DTC_FLAGS_bcm2837-rpi-3-b := -@
+DTC_FLAGS_bcm2837-rpi-3-b-plus := -@
+DTC_FLAGS_bcm2837-rpi-cm3-io3 := -@
+DTC_FLAGS_bcm2837-rpi-zero-2-w := -@
+DTC_FLAGS_bcm2711-rpi-400 := -@
+DTC_FLAGS_bcm2711-rpi-4-b := -@
+DTC_FLAGS_bcm2711-rpi-cm4-io := -@
+DTC_FLAGS_bcm2835-rpi-zero := -@
+DTC_FLAGS_bcm2835-rpi-zero-w := -@
 dtb-$(CONFIG_ARCH_BCM2835) += \
 	bcm2835-rpi-b.dtb \
 	bcm2835-rpi-a.dtb \
-- 
2.34.1

Re: [PATCH 0/2] arm/arm64: dts: Enable device-tree overlay support for RPi devices

[Uwe Kleine-König]

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Hello,

On Mon, Apr 11, 2022 at 12:59:38AM +0200, Aurelien Jarno wrote:
> This patchset changes the generation of the Raspberry Pi devices DTB
> files to improve the support for out-of-tree device-tree overlays, like
> it has recently been done for the Nvidia SoCs.
> 
> I personally only need that for arm64, but I have added a similar patch
> to do the same on arm.
> 
> Aurelien Jarno (2):
>   arm64: dts: broadcom: Enable device-tree overlay support for RPi
>     devices
>   arm: dts: Enable device-tree overlay support for RPi devices

I like these changes,

Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Given there was no feedback for >1 year now, I wonder if there are good
reasons against this change, or it just fell through the cracks?!

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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[PATCH 0/2] arm*/dts: Enable symbols for rpi device trees

[Uwe Kleine-König]

Hello,

based on an earlier submission by Aurelien Jarno, I rebased and slightly
simplified the patches.

There was some related irc conversion in #armlinux. Quoting the relevant
parts:

1685078851< ukleinek> arnd, [florian]: Who would pick up https://lore.kernel.org/linux-arm-kernel/20220410225940.135744-1-aurelien@aurel32.net ?
1685078920< ukleinek> arnd, [florian]: If there is an agreement in general that this is a good idea, I can coordinate with Aurelien that for arm64 there is a v2 with the simpler approach I pointed out.
1685083481< arnd> ukleinek: I have no objections to this, if [florian] wants to pick it up and send me for 6.5.
1685083809< arnd> robher: any comments on this one?
1685466520 < [florian]> ukleinek: I was hoping we would get an Ack for robher before picking it up in the brcm soc tree, don't want to ruffle any feathers unnecessarily

So it seems to start a beneficial chain reaction, only Rob's Ack is
needed.

As these two changes would greatly simplify the application of dtbos for
rpi hats, I look forward to Rob agreeing to them.

Best regards
Uwe

Aurelien Jarno (2):
  arm64: dts: broadcom: Enable device-tree overlay support for RPi
    devices
  arm: dts: Enable device-tree overlay support for RPi devices

 arch/arm/boot/dts/Makefile            | 18 ++++++++++++++++++
 arch/arm64/boot/dts/broadcom/Makefile |  4 ++++
 2 files changed, 22 insertions(+)

base-commit: ac9a78681b921877518763ba0e89202254349d1b
-- 
2.39.2

[PATCH 1/2] arm64: dts: broadcom: Enable device-tree overlay support for RPi devices

[Uwe Kleine-König]

From: Aurelien Jarno <aurelien@aurel32.net>

Add the '-@' DTC option for the Raspberry Pi devices. This option
populates the '__symbols__' node that contains all the necessary symbols
for supporting device-tree overlays (for instance from the firmware or
the bootloader) on these devices.

The Rasbperry Pi devices are well known for their GPIO header, that
allow various "HATs" or other modules do be connected and this enables
users to create out-of-tree device-tree overlays for these modules.

Please note that this change does increase the size of the resulting DTB
by ~40%. For example, with v6.4-rc1 increase in size is as follows:

  bcm2711-rpi-400.dtb       27556 -> 38141 bytes
  bcm2711-rpi-4-b.dtb       27484 -> 38069 bytes
  bcm2711-rpi-cm4-io.dtb    27373 -> 38076 bytes
  bcm2837-rpi-3-a-plus.dtb  14930 -> 20713 bytes
  bcm2837-rpi-3-b.dtb       15107 -> 20979 bytes
  bcm2837-rpi-3-b-plus.dtb  15463 -> 21443 bytes
  bcm2837-rpi-cm3-io3.dtb   14429 -> 20098 bytes
  bcm2837-rpi-zero-2-w.dtb  14781 -> 20524 bytes

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Link: https://lore.kernel.org/r/20220410225940.135744-2-aurelien@aurel32.net
[ukleinek: rebased to v6.4, replaced by a single assignment to DTC_FLAGS]
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 arch/arm64/boot/dts/broadcom/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/boot/dts/broadcom/Makefile b/arch/arm64/boot/dts/broadcom/Makefile
index 05d8c5ecf3b0..8b4591ddd27c 100644
--- a/arch/arm64/boot/dts/broadcom/Makefile
+++ b/arch/arm64/boot/dts/broadcom/Makefile
@@ -1,4 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
+
+# Enables support for device-tree overlays
+DTC_FLAGS := -@
+
 dtb-$(CONFIG_ARCH_BCM2835) += bcm2711-rpi-400.dtb \
 			      bcm2711-rpi-4-b.dtb \
 			      bcm2711-rpi-cm4-io.dtb \
-- 
2.39.2