what is the good way to edit the device tree ? and where is it ? (meta-sunxi) - yocto

Question

I have currently build a Yocto core-minimal-images (with meta-sunxi) for an orange pi zero board(a cheap chinese board that i use for my studies)
https://github.com/linux-sunxi/meta-sunxi
And it succesfully boot on my board,but in the /dev directory i didnt have acces to the SPI NOR memory. After some search on the orange pi wiki i find that i need some line to my device tree : https://linux-sunxi.org/Orange_Pi_Zero#Installing_from_linux
&spi0 {
status = "okay";
flash: m25p80#0 {
#address-cells = <1>;
#size-cells = <1>;
compatible = "winbond,w25q128";
reg = <0>;
spi-max-frequency = <40000000>;
};
};
But i dont really understand how to proceed...because i don't find which files i need to edit ? and maybe this not a good idee ? i think its better to create a .bbappend recipes no ?
the information that i have gather by searching in the meta-sunxi directories:
in conf/orange-pi-zero/KERNEL_DEVICETREE = "sun8i-h2-plus-orangepi-zero.dtb"
but there is no "sun8i-h2-plus-orangepi-zero.dts" file in the meta-sunxi directories ?
"sun8i-h2-plus-orangepi-zero.dtb"file is present in /build/tmp/deploy/images/orange-pi-zero/ so i don't really know how it is generated ? is it only download by yocto ? ( no device tree compilation ? )
by serachin on the net i was able to find sun8i-h2-plus-orangepi-zero.dts
at: https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts
and it contains theses interesting lines :
&spi0 {
/* Disable SPI NOR by default: it optional on Orange Pi Zero boards */
status = "disabled";
flash#0 {
#address-cells = <1>;
#size-cells = <1>;
compatible = "mxicy,mx25l1606e", "winbond,w25q128";
reg = <0>;
spi-max-frequency = <40000000>;
};
};
So maybe someone is able to give some advice to add SPI NOR support on my board ? what is the best way ? make some .bbappend ? or create my own meta by copying "meta-sunxi" and edit it ? and then which files i need to edit ?
thanks in advance for your time
Pierre.

Answer 1

Compiling the image with Yocto with the meta BSP layer pulls the kernel (checksout into tmp/work-shared/<MACHINE>/kernel-source/) and compiles it and you get the final output image which you can flash from tmp/deploy/images/<MACHINE>/. But in your case the mainline kernel doesn't enabled the SPI by default, so you need to enable it in the Linux Kernel source code.
If you have the Yocto build setup already, then you can edit the Device Tree and prepare the patch. You can move into tmp/work-shared/orange-pi-zero/kernel-source/ and edit the kernel source code and change
status = "okay";
and prepare the git patch using usually sequence,
git add arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts
git commit -s -m "Enable SPI by default"
git format-patch HEAD~
Then you append this patch in two ways.
Edit the recipes-kernel/linux/linux-mainline_git.bb and add your patch file into SRC_URI. Copy the patch file into recipes-kernel/linux/linux-mainline
If you don't want to edit the meta-sunxi layer, create linux-mainline_%.bbappend in your meta layer and do the same.
The below patch can be directly applied to meta-sunxi to fix this case. You can find the same here.
From 3a1a3515d33facdf8ec9ab9735fb9244c65521be Mon Sep 17 00:00:00 2001
From: Parthiban Nallathambi <parthiban#linumiz.com>
Date: Sat, 10 Nov 2018 12:20:41 +0100
Subject: [PATCH] orange pi zero: Add SPI support by default
Signed-off-by: Parthiban Nallathambi <parthiban#linumiz.com>
---
...rm-dts-enable-SPI-for-orange-pi-zero.patch | 26 +++++++++++++++++++
recipes-kernel/linux/linux-mainline_git.bb | 1 +
2 files changed, 27 insertions(+)
create mode 100644 recipes-kernel/linux/linux-mainline/0001-arm-dts-enable-SPI-for-orange-pi-zero.patch
diff --git a/recipes-kernel/linux/linux-mainline/0001-arm-dts-enable-SPI-for-orange-pi-zero.patch b/recipes-kernel/linux/linux-mainline/0001-arm-dts-enable-SPI-for-orange-pi-zero.patch
new file mode 100644
index 0000000..e6d7933
--- /dev/null
+++ b/recipes-kernel/linux/linux-mainline/0001-arm-dts-enable-SPI-for-orange-pi-zero.patch
## -0,0 +1,26 ##
+From 1676d9767686404211c769de40e6aa55642b63d5 Mon Sep 17 00:00:00 2001
+From: Parthiban Nallathambi <parthiban#linumiz.com>
+Date: Sat, 10 Nov 2018 12:16:36 +0100
+Subject: [PATCH] arm: dts: enable SPI for orange pi zero
+
+Signed-off-by: Parthiban Nallathambi <parthiban#linumiz.com>
+---
+ arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts b/arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts
+index 0bc031fe4c56..0036065da81c 100644
+--- a/arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts
++++ b/arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts
+## -144,7 +144,7 ##
+
+ &spi0 {
+ /* Disable SPI NOR by default: it optional on Orange Pi Zero boards */
+- status = "disabled";
++ status = "okay";
+
+ flash#0 {
+ #address-cells = <1>;
+--
+2.17.2
+
diff --git a/recipes-kernel/linux/linux-mainline_git.bb b/recipes-kernel/linux/linux-mainline_git.bb
index 5b8e321..9b2bcbe 100644
--- a/recipes-kernel/linux/linux-mainline_git.bb
+++ b/recipes-kernel/linux/linux-mainline_git.bb
## -27,5 +27,6 ## SRCREV_pn-${PN} = "b04e217704b7f879c6b91222b066983a44a7a09f"
SRC_URI = "git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git;protocol=git;branch=master \
file://defconfig \
+ file://0001-arm-dts-enable-SPI-for-orange-pi-zero.patch \
"
S = "${WORKDIR}/git"
--
2.17.2