Connecting ST7796s display via panel-mipi-dbi-spi

[HeavyPunk]

Hello! I'm trying to connect my display based on ST7796s to SoC Radxa Zero 3W using your driver but i have some issues.
Display doesn't work but dmesg logs looks like it really working.

Info about my setup:

Armbian (build on 6.18-rc2 kernel version)
DTS:

/dts-v1/;
/plugin/;

/ {
  fragment@0 {
    target = <&spi3>;
    __overlay__ {
      status = "okay";
      #address-cells = <1>;
      #size-cells = <0>;
      pinctrl-names = "default", "high_speed";
      pinctrl-0 = <&spi3m1_cs0 &spi3m1_pins>;
      pinctrl-1 = <&spi3m1_cs0 &spi3m1_pins_hs>;
      cs-gpios = <&gpio4 22 1>;
      max-freq = <50000000>;

      st7796: panel@0 {
        compatible = "panel", "panel-mipi-dbi-spi";
        reg = <0>;
        spi-max-frequency = <50000000>;

        width-mm = <55>;
        height-mm = <83>;
	width = <480>;
	height = <320>;

        dc-gpios = <&gpio3 12 1>;
        reset-gpios = <&gpio3 11 1>;
	backlight-gpios = <&gpio3 19 1>;

        panel-timing {
          hactive = <480>;
          vactive = <320>;
          hback-porch = <0>;
          vback-porch = <0>;

          clock-frequency = <0>;
          hfront-porch = <0>;
          hsync-len = <0>;
          vfront-porch = <0>;
          vsync-len = <0>;
        };
      };
    };
  };
};

Initialization sequence:

The first variant:

command 0x28
delay 120
command 0x01
delay 120
command 0x11
delay 120
command 0xF0 0xC3
command 0xF0 0x96
command 0x36 0x20
command 0x3A 0x05
command 0xB0 0x80
command 0xB6 0x00 0x02
command 0xB5 0x02 0x03 0x00 0x04
command 0xB1 0x80 0x10
command 0xB4 0x00
command 0xB7 0xC6
command 0xC5 0x24
command 0xE4 0x31
command 0xE8 0x40 0x8A 0x00 0x00 0x29 0x19 0xA5 0x33
command 0xC1 0x06
command 0xC2 0xA7
command 0xC5 0x18
delay 120
command 0xE0 0xF0 0x09 0x0b 0x06 0x04 0x15 0x2F 0x54 0x42 0x3C 0x17 0x14 0x18 0x1B
command 0xE1 0xE0 0x09 0x0B 0x06 0x04 0x03 0x2B 0x43 0x42 0x3B 0x16 0x14 0x17 0x1B
delay 120
command 0xF0 0x3C
command 0xF0 0x69
delay 120
command 0x29
delay 120

The second variant (taken from wiki here):

delay 120
command 0x01
delay 120
command 0x11
delay 120
command 0xF0 0xC3
command 0xF0 0x96
command 0x36 0x48
command 0x3A 0x55
command 0xB4 0x01
command 0xB6 0x80 0x02 0x3B
command 0xE8 0x40 0x8A 0x00 0x00 0x29 0x19 0xA5 0x33
command 0xC1 0x06
command 0xC2 0xA7
command 0xC5 0x18
delay 120
command 0xE0 0xF0 0x09 0x0b 0x06 0x04 0x15 0x2F 0x54 0x42 0x3C 0x17 0x14 0x18 0x1B
command 0xE1 0xE0 0x09 0x0B 0x06 0x04 0x03 0x2B 0x43 0x42 0x3B 0x16 0x14 0x17 0x1B
delay 120
command 0xF0 0x3C
command 0xF0 0x69
delay 120
command 0x29

Both of them doesn't work. The first variant taken from other driver for tinydrm.
This sequence was tested with driver for fbtft and it works fine. But fbtft deprecated and i can't use it for my purposes. Fbtft driver was tested with 6.1.115 kernel.

Also, I share with you logs related to DRM from dmesg
drm.log

Could you help me please 🙏 ? I wil share any information about my config if you need.

Also, when system is booting i see display is blinking (looks like just backlight dimming)

[HeavyPunk]

The display I use is https://www.lcdwiki.com/4.0inch_Capacitive_SPI_Module_ST7796

[robertojguerra]

Can you try the text or bin firmware file for ST7796s found in this thread:

https://forums.raspberrypi.com/viewtopic.php?t=380704

But with my method for armbian, using the same driver panel-mipi-dbi

https://forum.armbian.com/topic/47971-driving-the-ili9488-lcd-40-inch-cheap-chinese-clone/#findComment-208446

Of course, you would need to change the GPIO and SPI pins, from Orange Pi Zero 3 to Radxa Zero 3W

There's also a success case here: #8

[HeavyPunk]

So....
I really don't understand what's just happened but display is alive!!
All what I did it's just decrease SPI speed here: spi-max-frequency = <50000000>; to 48MHz, removed unused properties in DTS (make it as your DTS) and load your initialization sequence.
But I need to make a bit change of display settings because of invalid layout (just wanna try my previous initialization sequences)
Thank you very much for your help!!! You actually save a many hours of my life 😄
I'll post here my configs for other users a bit later when i'll complete the setup

[robertojguerra]

I am glad it worked :)
Yes. Post your solution... I hope you don't have problems with X11 and touch (for project reasons, I stick with resistive touch).

[HeavyPunk]

Currently I use wayland + xwayland and Phosh shell. It's working fine, I don't get any problems with that.
The module use FT6236u touch controller and i haven't internal driver for it but my custom driver under development now, it can be placed here when i'll be sure it will work good. I can place here the link to driver here, how do you think?

[robertojguerra]

It would be best if you post publish it in the armbian forum... since this github is specific for panel-mipi-dbi stuff.

[HeavyPunk]

My latest setup is:
Display module: ST7796S
Default layout: landscape

DTS for display (using SPI3 on 100MHz speed):

/dts-v1/;
/plugin/;

/ {
  fragment@0 {
    target = <&spi3>;
    __overlay__ {
      status = "okay";
      #address-cells = <1>;
      #size-cells = <0>;
      pinctrl-names = "default", "high_speed";
      pinctrl-0 = <&spi3m1_cs0 &spi3m1_pins>;
      pinctrl-1 = <&spi3m1_cs0 &spi3m1_pins_hs>;
      cs-gpios = <&gpio4 22 1>;
      max-freq = <100000000>;

      st7796: panel@0 {
        compatible = "panel", "panel-mipi-dbi-spi";
        reg = <0>;
        spi-max-frequency = <100000000>;

        width-mm = <84>;
        height-mm = <56>;

        dc-gpios = <&gpio3 12 0>;
        reset-gpios = <&gpio3 11 0>;
	format = "b6x2g6x2r6x2";
	write-only;

        panel-timing {
          hactive = <480>;
          vactive = <320>;
          hback-porch = <0>;
          vback-porch = <0>;

          clock-frequency = <0>;
          hfront-porch = <0>;
          hsync-len = <0>;
          vfront-porch = <0>;
          vsync-len = <0>;
        };
      };
    };
  };
};

Initialization sequence:

command 0x28
delay 120
command 0x01
delay 120
command 0x11
delay 120
command 0xF0 0xC3
command 0xF0 0x96
command 0x36 0x20 # landscape mode
command 0x3A 0x66 # BGR666 pixel format
command 0xB0 0x80
command 0xB6 0x00 0x02
command 0xB5 0x02 0x03 0x00 0x04
command 0xB1 0x80 0x10
command 0xB4 0x00
command 0xB7 0xC6
command 0xC5 0x24
command 0xE4 0x31
command 0xE8 0x40 0x8A 0x00 0x00 0x29 0x19 0xA5 0x33
command 0xC1 0x06
command 0xC2 0xA7
command 0xC5 0x18
delay 120
command 0xE0 0xF0 0x09 0x0b 0x06 0x04 0x15 0x2F 0x54 0x42 0x3C 0x17 0x14 0x18 0x1B
command 0xE1 0xE0 0x09 0x0B 0x06 0x04 0x03 0x2B 0x43 0x42 0x3B 0x16 0x14 0x17 0x1B
delay 120
command 0xF0 0x3C
command 0xF0 0x69
delay 120
command 0x29
delay 120

[robertojguerra]

The pixel color format = "b6x2g6x2r6x2" is only needed in ili9486 and ili9488.

Can you try it without that line? And change the BGR666 initialization sequence, to RGB565 (command 0x3a 0x55).
Maybe you will get RGB565 format, which requires 33% less bytes and may result in 50% more frames per second.

Details: https://github.com/notro/panel-mipi-dbi/wiki#rgb666
https://gitlab.freedesktop.org/drm/misc/kernel/-/blob/drm-misc-next/Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml

[HeavyPunk]

Thank you that you point me of this.
I tried this way and it really increase speed of display
But also I need to switch these commands:

command 0x36 0x28 # landscape mode + BGR color mode
command 0x3A 0x55 # BGR565

and remove format property in DTS file.

On my display RGB565 panel-mipi-dbi-spi mode is equals to BGR565 (i don't know why)