Note: I did not write this driver. I only modified it to clean up compiler warnings/errors. The original(Sharp Memory LCD Kernel Driver) can be found here: (http://www.librecalc.com/en/wp-content/uploads/sites/4/2014/10/sharp.c)
More information can be found here: (http://www.librecalc.com/en/downloads/)
The original code appears to be LCD made by shap. Therefore, we used this code as a reference for JDI MIP LCD:(https://github.com/a8ksh4/JDI-LCD-Kernel-Driver)
Also, when installing on Radxa zero, I used this code as a reference for the Device Tree Overlay:(https://github.com/imnotjames/Sharp-Memory-LCD-Kernel-Driver/tree/radxa-zero-hacks)
This driver is for the LPM027M128B.
Connect the following pins:
| Display | Radxa Zero Pin |
|---|---|
| SCLK | 23 (SPI_B_SCLK) |
| SI | 19 (SPI_B_MOSI) |
| SCS | 24 (SPI_B_SS0) |
| EXTCOMIN | 16 (GPIOX_10) |
| DISP | 18 (GPIOX_8) |
| VDDA | GND |
| VDD | GND |
| EXTMODE | +3.3V |
| VSSA | +3.3V |
| VSS | +3.3V |
If you want to change the connection pins, change jdi_mip.dtsi.
Verify that you have the linux kernel headers for your platform.
sudo apt install make gcc build-essential device-tree-compiler
sudo apt install linux-headers-$(uname -r)
To compile the driver, run:
make
To install the driver, run:
sudo make modules_install
Update the module dependencies and test if they are loaded correctly:
sudo depmod -a
sudo modprobe jdi_mip
If you want the module to load at boot you'll need to add it to the /etc/modules file, like:
...
# This file contains...
# at boot time...
jdi_mip
When you make, mji_mip.dtbo should be generated from mji_mip.dtsi through mji_mip.dts.
To load it at runtime, copy it to /boot/dtbs/$(uname -r)/amlogic/overlay/:
sudo cp jdi_mip.dtbo /boot/dtbs/$(uname -r)/amlogic/overlay/
And then modify the following line to /boot/uEnv.txt:
overlays=meson-g12a-uart-ao-a-on-gpioao-0-gpioao-1 jdi_mip
param_spidev_spi_bus=1
param_spidev_max_freq=20000000
If the module is loaded correctly, the framebuffer will be recognized as /dev/fb0 and the console will be assigned /dev/tty1.
However, if /dev/fb1 is subsequently added because of HDMI, tty1 will become inactive.
To activate tty1 again, execute the following command
sudo chvt 1
If you want to activate it automatically at boot time, use systemd or similar.
Create /etc/systemd/system/chvt1.service
[Unit]
Description=Switch to /dev/tty1
[Service]
ExecStart=/bin/bash
ExecStart=/bin/bash -c "sleep 5 && chvt 1"
Type=oneshot
[Install]
WantedBy=multi-user.target
Here, the command on the ExecStart line will wait for 5 seconds before executing chvt 1.
After saving this file, make systemd aware of the new service with the following command:
sudo chmod +x /etc/systemd/system/chvt1.service
sudo systemctl daemon-reload
Then, activate this new service with the following command so that it will run automatically at system startup:
sudo systemctl enable chvt1
If you want to log in automatically on tty1, use the sudo systemctl edit getty@tty1 command and write the following information.
[Service]
ExecStart=
ExecStart=-/sbin/agetty --autologin rock %I 38400 linux
This will automatically log you in as the default user "rock". If you want to log in as a different user, please change the user name.
Finally, reboot the system to verify that the configuration works correctly:
sudo reboot