This helps building the ili9163 SPI TFT display tinydrm Linux kernel driver out of tree.
The source of the kernel module is https://patchwork.kernel.org/project/dri-devel/list/?series=457553 (disregard the wrong patch title), by Daniel Mack
Provided is also a device tree overlay file to connect the display to a Raspberry PI with the following connections:
| RPi function | RPi physical pin | display physical pin | display function |
|---|---|---|---|
| GND | 1 | GND | |
| 3.3V | 2 | VDD | |
| 3.3V | 3 | VDD | |
| CS0, GPIO 8 | 24 | 4 | /CS |
| GPIO 23 | 16 | 5 | /RST |
| MOMI | 19 | 6 | SDIO |
| GND | 7 | GND | |
| GPIO 18 | 12 | 8 | D/C |
| SCL | 23 | 9 | SCL |
| GND | 10 | GND | |
| 3.3V | 11 | 4-wire mode | |
| GND | 20 | GND | |
| 3.3V | 17 | LED Anode | |
| GND | 18 | LED Kathode | |
| GND | 19 | LED Kathode |
For (cross-)compiling for Raspberry Pi you'll need a kernel source tree that matches your pi. If you're using a standard Raspbian kernel you can follow the instructions at https://www.raspberrypi.org/documentation/linux/kernel/building.md and https://lostindetails.com/articles/compiling-a-kernel-module-for-the-raspberry-pi-2
On the pi:
FIRMWARE_HASH=$(zgrep "* firmware as of" /usr/share/doc/raspberrypi-bootloader/changelog.Debian.gz | head -1 | awk '{ print $5 }')
KERNEL_HASH=$(wget https://raw.github.com/raspberrypi/firmware/$FIRMWARE_HASH/extra/git_hash -O -)
echo $KERNEL_HASHThis will output a commit hash, such as 081f560bde7188ca6f40cf297bd55c680e0179c0.
Then on your build host do:
sudo apt install git bc bison flex libssl-dev make libc6-dev libncurses5-dev
sudo apt install crossbuild-essential-armhf
git clone https://github.com/raspberrypi/linux raspberrypi-linux
cd raspberrypi-linux
git checkout 081f560bde7188ca6f40cf297bd55c680e0179c0Default configuration and build command differs between Raspberry Pi hardware versions, see the documentation linked above. For Pi 0 do, on your buildhost:
KERNEL=kernel
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- bcmrpi_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- -j5 zImage modules dtbsNow you have a fully built and usable Raspberry Pi linux kernel tree in raspberrypi-linux.
To build the module and device tree overlay in this directory you'll need to provide the path, such as ../raspberrypi-linux/ to the linux source directory. Then simply do
make KDIR=../raspberrypi-linux/ ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf-To install the module, copy the resulting ili9163.ko into /lib/modules/$(uname -r)/extra/ and run sudo depmod -a. Also, create a /etc/modules-load.d/ili9163.conf with a single line ili9163 to have the module autoloaded at boot (for some reason it's not automatically loaded by the device tree, FIXME).
To install the kbdisp.dtbo file, copy it into /boot/overlays/ and append the line dtoverlay=kbdisp to /boot/config.txt.
Note: Even when the module is loaded and the /dev/fb1 device is created, the display is not enabled by default: /sys/class/drm/card0-SPI-1/enabled shows disabled. I have not found the 'correct' way to enable it.
Hacky: Opening /dev/dri/card0 seems to enable the display, even without writing anything into it. Simply do cat /dev/zero > /dev/dri/card0 and ignore the 'invalid argument' error.
More proper: By editing /boot/cmdline.txt you can use the fbcon module to activate a console (tty) on the display.
Two variants: append fbcon=map:10 to the command line to swap SPI display and broadcom video core, so the SPI display becomes tty1 and the normal raspberry pi display becomes tty2. You'll get normal linux/systemd boot messages on the SPI display.
Or: append fbcon=map:01 to the command line. Now the SPI display will be tty2, which is normally unused and no output is written to it, but it is under control of fbcon and enabled.
To test:
sudo apt install fbi
sudo fbi -T 1 -d /dev/fb1 /usr/share/icons/hicolor/32x32/apps/rpi.pngNote: fbi tends to hang around. Do a killall fbi afterwards.