The touchscreen (official RPi 7") no longer registers touch input after moving from Sarpi kernel 4.19.x to 5.4.x. Screen display works fine, backlight works fine, keyboard & mouse works fine.

TIL after some hours of digging -

In 4.19 the config option was CONFIG_TOUCHSCREEN_RPI_FT5406=m, which generates the module kernel/drivers/input/touchscreen/rpi-ft5406.ko.

Since 4.20 or 4.21, a driver was mainstreamed and the option is now CONFIG_TOUCHSCREEN_RASPBERRYPI_FW=m, which generates the module kernel/drivers/input/touchscreen/raspberrypi-ts.ko

Things I tried with no luck on the 5.4.16 kernel:
* modprobe raspberrypi-ts: nothing shows up in dmesg
* Added /sbin/modprobe raspberrypi-ts to /etc/rc.d/rc.modules.local and reboot
* Modified /boot/config.txt to add dtoverlay=rpi-ft5406 (but I never needed to do this before)
* Searched online for a while with no luck

Next I would probably need to install Raspbian on a new drive and see if the touchscreen works there, and try to get hints as to what they may be doing right.

I'm guessing it has something to do with missing modules. It would be prudent to do a 'lsmod' while running kernel 4.19.x and then compare with the same from kernel 5.4.x and see what the differences are. Testing with Raspbian would only be eventful if they are running kernel 5.4.x because last time I checked they were still on the 4.19.97 release. You can always 'upgradepkg' using the older kernel 4.19.x SARPi packages and revert to your previous settings/setup.

[EDIT] I just checked the SARPi4 (Raspberry Pi 4) kernel 5.4.16 .config and it tells me:

[EDIT#2] I just checked the SARPi3 (Raspberry Pi 3) kernel 5.4.16 .config and it tells me:

[EDIT#3] I just checked the SARPi2 (Raspberry Pi 2) kernel 5.4.16 .config and it tells me:

There must be something else causing this issue. I don't have a touchscreen so I'm unable to assist with any practical support.

[EDIT#4] I just checked the SARPi3 (Raspberry Pi 3) kernel 4.19.89 .config and found this:

But there doesn't appear to be a setting for 'CONFIG_TOUCHSCREEN_RASPBERRYPI_FW' in the RPi3 kernel 4.19.89 .config

@Exaga thanks for looking into this!

I believe that's correct, that the relevant change causing the issue is the change from:
4.19: CONFIG_TOUCHSCREEN_RPI_FT5406=m

to

4.20/1 and later: CONFIG_TOUCHSCREEN_RASPBERRYPI_FW=m

Raspbian is still on 4.19 so nothing I can currently learn from there. I'll wait for Raspbian to rev to a newer kernel and see what I can learn once they do that.

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OF COURSE! It's very much in my interest to ensure any software released by the SARPi Project is working as expected so I need to look into problems such as yours.

Also thanks for letting me know about this problem because it does highlight an issue which I would never have found - as I don't use touchscreen. I have done some research online about the official 7" touchscreen on the RPis and it seems that it can be a troublesome affair on most Linux distros - including Raspbian! I'm not surprised you found it difficult to locate information to help in problem-solving because I found the same thing, unless you are using Raspbian! haha!

Waiting for the RPi guys to decide which kernel version they will ship next after 4.19 is one option available to you. Troubleshooting and testing yourself is another (I read that users have been successful on Ubuntu and Gentoo with this touchscreen). Installing a previous 4.19 kernel and modules will undoubtabley solve your issue until a later date. I know that's only a stop-gap but your Raspberry Pi 3 won't be any worse off for it.

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Tried a couple of other things -

Touchscreen module under Linux 4.19.89-v7-arm:
$ rmmod rpi_ft5406: touchscreen stops working
$ modprobe rpi_ft5406: touchscreen works again

Compared lsmod:
$ lsmod (on Linux 4.19.89-v7-arm)
$ lsmod (on Linux 5.4.16-v7-arm)

-> The only modules that are missing moving from 4.19 to 5.4 are v4l2_common (not relevant to touch) and rpi_ft5406 (runs touchscreen under 4.19).

I'll look into Gentoo/Ubuntu and see what I can learn.

Thanks again.

It might be possible to 'borrow' from other distributions; whatever firmware/modules are needed to make the hardware work. Any OS would probably have to be running the same kernel major version but you'd surely find out through 'trial and error' testing to see what worked, or not as the case may be. Given that this can be simple, or a complete PITA, it's up to you to decide if it's worth it while there are alternatives.

FWIW: If I were in your shoes I'd revert to kernel 4.19.x release and wait a while, if touchscreen was that crucial to the setup. You might find that after spending considerable time (days/weeks/months) solving this problem - with or without success - that something somewhere else gets fixed upstream and your efforts have been somewhat squandered. It's happened to me a few times in my experience, and it's so damned annoying!

Touchscreen works again on newest sarpi kernel 5.4.18-v7-arm! Not sure what magic made it happen .

Then, thanks to the RPi guys for that because something obviously got fixed upstream - saving me the time and effort of butchering it myself.

Turns out the issue was fixed by an updated rpi-ft5406.dtbo overlay.

I confirmed by copying rpi-ft5406.dtbo from the contents of the package sarpi3-boot-firmware-armv7-1_slackcurrent_08Feb20_sp1 to my system running 5.4.16 and sarpi3-boot-firmware-armv7-1_slackcurrent_31Jan20_sp1 and this made the touchscreen work under 5.4.16 after rebooting.

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The Raspberry Pi device tree blobs are supported from userspace by means of 'overlays' but they're actually built off the back of the kernel [a.k.a. 'make dtbs'] just like the modules - i.e. from the same source code as the kernel, etc. This page gives you some idea of the order of things: https://www.raspberrypi.org/document...el/building.md

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