Hi,
On 31/07/2023 03:46, MOESSBAUER, Felix wrote:
On Mon, 2023-07-31 at 00:12 +0200, Jernej Škrabec wrote:
Dne sreda, 19. julij 2023 ob 14:26:13 CEST je Moessbauer Felix
napisal(a):
On Tue, 2023-07-11 at 21:42 +0200, Jernej Škrabec wrote:
Dne torek, 27. junij 2023 ob 15:37:03 CEST je Felix Moessbauer
napisal(a):
Add the '-@' DTC option for the sun8i-h3 pi-class 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.
These devices allow various modules to 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 ~30%. For example, with v6.4 increase in size is as follows:
22909 -> 29564 sun8i-h3-orangepi-lite.dtb
24214 -> 30935 sun8i-h3-bananapi-m2-plus.dtb
23915 -> 30664 sun8i-h3-nanopi-m1-plus.dtb
22969 -> 29537 sun8i-h3-nanopi-m1.dtb
24157 -> 30836 sun8i-h3-nanopi-duo2.dtb
24110 -> 30845 sun8i-h3-orangepi-plus2e.dtb
23472 -> 30037 sun8i-h3-orangepi-one.dtb
24600 -> 31410 sun8i-h3-orangepi-plus.dtb
23618 -> 30230 sun8i-h3-orangepi-2.dtb
22170 -> 28548 sun8i-h3-orangepi-zero-plus2.dtb
23258 -> 29795 sun8i-h3-nanopi-neo-air.dtb
23113 -> 29699 sun8i-h3-zeropi.dtb
22803 -> 29270 sun8i-h3-nanopi-neo.dtb
24674 -> 31318 sun8i-h3-nanopi-r1.dtb
23477 -> 30038 sun8i-h3-orangepi-pc.dtb
24622 -> 31380 sun8i-h3-bananapi-m2-plus-v1.2.dtb
23750 -> 30366 sun8i-h3-orangepi-pc-plus.dtb
Signed-off-by: Felix Moessbauer <felix.moessbauer@xxxxxxxxxxx>
---
Please note that I only tested the overlay on the sun8i-h3-
nanopi-
neo
device. However, the devices are quite similar and in general
the
change to add symbols should be pretty safe. Similar patches
have
been
applied to various other devices in the past without any
negative
effect (except for the increased size).
I'm not a fan of this approach. What's wrong with letting kernel
builders
specify this flag on their own at compile time? That way size is
still
completely in domain of builder.
That's easier said than done. These symbols are only needed for
some
targets (that are commonly used with overlays). But how should a
general purpose kernel builder like Debian know which DT to build
with
symbols and which without? In Yocto the overlays are not really
needed,
as often the original dts is just patched directly.
LibreELEC (distro I help with) has support for DT overlays for some
time and
it was easy to enable symbols for all DTs with simple "DTC_FLAGS=-@"
addition
So why don't you use the U-Boot provided copy of the DTB? We sync the
DTs regularly from the kernel repo to the U-Boot repo, and the U-Boot
build system builds all DTBs with overlay support already.
This also saves you from the hassle to actually find and load the right
DTB, as it automatically comes as part of the U-Boot binary.
On the U-Boot prompt (or rather in a script) you would then do:
=> fdt move $fdtcontroladdr $fdt_addr_r
=> load <source> $fdtoverlay_addr_r <your_overlay>.dtbo
=> fdt apply $fdtoverlay_addr_r
You could also chime in on this U-Boot patch of mine, that loads and
applies all .dtbo files found in a given directory:
https://lore.kernel.org/u-boot/20230210110213.2531190-1-andre.przywara@xxxxxxx/
Cheers,
Andre
Thanks for the pointer. If this would be a kconfig option, I would
agree. There's a patch to add this option, but this did not get
accepted [3]. Just manually adding some "magic" options does not feel
correct.
to build command [1]. Do you see any downside except knowing you have
to
include it? On the upside, there is no need to patch each and every
file and
kernel builder has a choice if overlays should be supported or not.
There is a similar feature request for Debian, but without a decision
yet [4]. I just cross-referenced it to this thread.
Note that
in some cases overlays can be needed even in the case when board
doesn't have
expansion ports.
If that is the case, why can't we at least add the patch from [3] and
provide the distros an easy option to enable overlays? Once integrated,
we can eventually get rid of all the per-device patches in the kernel.
Best regards,
Felix
[3] https://www.spinics.net/lists/kernel/msg4252361.html
[4] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=910727
Best regards,
Jernej
[1]
https://github.com/LibreELEC/LibreELEC.tv/blob/master/packages/linux/
package.mk#L213
There has been a discussion in 2017 to improve the situation in
general, but without any final decision or implementation [1]. By
that,
these patches got more and more common. I recently sent a very
similar
patch for a riscv board that got accepted [2].
IMHO it is better to have these patches in the kernel instead of
carrying different variants of this in each Linux distro. IMHO, the
board vendors themselves should add this when they add a board.
[1]
https://lore.kernel.org/lkml/1502831736-28282-1-git-send-email-trini@konsulk
o.com/ [2]
https://lore.kernel.org/linux-devicetree/20230627080620.329873-1-felix.moess
bauer@xxxxxxxxxxx/
Best regards,
Felix
Best regards,
Jernej
Felix Moessbauer
Siemens AG
arch/arm/boot/dts/allwinner/Makefile | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/arch/arm/boot/dts/allwinner/Makefile
b/arch/arm/boot/dts/allwinner/Makefile index
589a1ce1120a..eebb5a0c873a
100644
--- a/arch/arm/boot/dts/allwinner/Makefile
+++ b/arch/arm/boot/dts/allwinner/Makefile
@@ -179,6 +179,25 @@ dtb-$(CONFIG_MACH_SUN7I) += \
sun7i-a20-pcduino3-nano.dtb \
sun7i-a20-wexler-tab7200.dtb \
sun7i-a20-wits-pro-a20-dkt.dtb
+
+# Enables support for device-tree overlays for all pis
+DTC_FLAGS_sun8i-h3-orangepi-lite := -@
+DTC_FLAGS_sun8i-h3-bananapi-m2-plus := -@
+DTC_FLAGS_sun8i-h3-nanopi-m1-plus := -@
+DTC_FLAGS_sun8i-h3-nanopi-m1 := -@
+DTC_FLAGS_sun8i-h3-nanopi-duo2 := -@
+DTC_FLAGS_sun8i-h3-orangepi-plus2e := -@
+DTC_FLAGS_sun8i-h3-orangepi-one := -@
+DTC_FLAGS_sun8i-h3-orangepi-plus := -@
+DTC_FLAGS_sun8i-h3-orangepi-2 := -@
+DTC_FLAGS_sun8i-h3-orangepi-zero-plus2 := -@
+DTC_FLAGS_sun8i-h3-nanopi-neo-air := -@
+DTC_FLAGS_sun8i-h3-zeropi := -@
+DTC_FLAGS_sun8i-h3-nanopi-neo := -@
+DTC_FLAGS_sun8i-h3-nanopi-r1 := -@
+DTC_FLAGS_sun8i-h3-orangepi-pc := -@
+DTC_FLAGS_sun8i-h3-bananapi-m2-plus-v1.2 := -@
+DTC_FLAGS_sun8i-h3-orangepi-pc-plus := -@
dtb-$(CONFIG_MACH_SUN8I) += \
sun8i-a23-evb.dtb \
sun8i-a23-gt90h-v4.dtb \
