PI 7" Screen DSI issue on RPI 5 Board

donmahallem commented 6 months ago

Describe the bug

The official touchscreen doesn't work on the PI5(stays off, no sign of light or output). With the exact same SD-Card(same installation) on the RPI 3 Board the screen just works.

Steps to reproduce the behaviour

Attach screen via DSI to either DSI0 or DSI1 to the PI5. Specify in /boot/firmware/config.txt as required by the official documentation the DSI output port the screen uses.

dtoverlay=vc4-kms-v3d (did even try to specify the -pi5 version)
dtoverlay=vc4-kms-dsi-7inch,dsi0

Looking at raspinfo once the correct DSI port is specified the I2C controller times out:

[    4.071932] i2c_designware 1f00088000.i2c: controller timed out
[    4.071950] rpi_touchscreen_attiny 6-0045: Failed to read REG_ID reg: -5
[    4.071961] rpi_touchscreen_attiny: probe of 6-0045 failed with error -5

This doesn't happen when no DSI cable is connected or the incorrect dsi output for the 7inch screen is specified.

Device (s)

Other

System

https://pastebin.com/teagmKfa

Logs

No response

Additional context

No response

6by9 commented 6 months ago

What cable have you used to connect the Pi5 to the display? Pi Zero Camera cables can NOT be used for displays, and tend to result in I2C timeouts as you have due to SCL being tied low. (See https://forums.raspberrypi.com/viewtopic.php?t=362563 for having gone through exactly that loop).

Note that there are separate camera and display cables listed on the Pi product page - https://www.raspberrypi.com/products

Vizzyy commented 2 months ago

Running into similar issues with the official 7" display on my pi5. I'm attempting to completely clone my setup I had on my pi4 onto the 5, but am having to start from scratch as the pi5 requires bookworm. I'm using an official rpi5 display cable -- as others have noted, you can't just use a pi zero camera cable.

The display powers up and works, so does the touch, but I can't get the rpi_backlight python module to work on the pi5.

I noticed that in this directory /sys/class/backlight/ the screen device shows up at 6-0045 (which is how I found this thread, by googling that string), while on the pi4 it used to be 10-0045. There's something weirdly different with how the pi5 is interfacing with the display, on a hardware level.

Judging by the full hardware path: ../../devices/platform/axi/1000120000.pcie/1f00088000.i2c/i2c-6/6-0045/backlight/6-0045 i'm guessing it's the introduction of the pcie ?

6by9 commented 2 months ago

Seeing as you say your display and touch works, it is not the same issue that donmahallem has reported.

The Pi5 has 2 camera/display ports, and routes i2c-4 and i2c-6 to them. Pi4 has one camera and one display port. i2c-10 is routed to both as image sensors normally have different I2C addresses to the display.

It looks like rpi_backlight makes big assumptions about where the backlight driver will exist - https://github.com/linusg/rpi-backlight/blob/main/rpi_backlight/__init__.py#L31-L35. I see you've already found that repo and commented on https://github.com/linusg/rpi-backlight/issues/60 That is a third party library, so it's largely up to the developers (or others seeing as it is all open source) to add support. It's not an issue in the kernel.

raspberrypi / linux