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[UNOFFICIAL][EXPERIMENT] TWRP for Galaxy Tab S7 Wifi

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Bushcat

Member
Nov 14, 2018
25
1
23
Samsung Galaxy S5 Mini
OnePlus 6T
At this point, I really want to think that the issue has something to do with how we're setting up/driving the display. I'm leaning away from it being an outright problem with the kernel (and definitely don't think it's the device tree), but I do wonder if the information in the kernel logs might help us find the problem.

In comparing logs from stock recovery (where video obviously works) with logs from TWRP, I can see some notably different values getting used for initial backlight/brightness settings, as well as some other differences related to the display.

Now, I don't know that the differences I've spotted actually matter, but the display in the T870 is obviously a different model than the larger one in the T976, where TWRP is functional, so it's certainly something to check at least. For now that's all I've really got, but I'll be digging into this more soon.
I can send you the log of T970 twrp and I can make los recovery and pbrp for the tab s7, maybe that has an effect because there was an effect with pbrp on the tab s7+, the tab s7+ has a small glitching strip that appears sometimes but is barely noticable but in pbrp it appears wiith every interaction, I was able to lower it but I couldn't fix it. Sometimes other recoveries work better than twrp, for example the oneplus 8 lineage recovery works better than twrp. Somebody suggested me to build the kernel inline with twrp because samsung had issues in the past, I tried with all the firmware files for our device and it fixed the timezone bug but nothing else.
 

bxlentpartyon

Member
Aug 19, 2020
47
47
I can send you the log of T970 twrp and I can make los recovery and pbrp for the tab s7, maybe that has an effect because there was an effect with pbrp on the tab s7+, the tab s7+ has a small glitching strip that appears sometimes but is barely noticable but in pbrp it appears wiith every interaction, I was able to lower it but I couldn't fix it.
I'd really appreciate any relevant (or semi-relevant) logs you can provide, as it all gives me data to compare to what I'm seeing. Thanks for offering!
 
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kabirsaad2007

Member
Jan 18, 2012
22
0
33
surat
Samsung Galaxy Z Fold2
This is my first thread of this kind, so bear with me if I'm not formatting it quite right.

I've run a test build of TWRP 3 for the Galaxy Tab S7 Wifi (T870) against a customized version of the kernel that shipped with the T870OXM2BUC6 firmware. At this point, this is completely untested, as I do not currently have my tablet in a state where I can test it (I'm working on this).

Here is a link to the recovery image on my Google Drive:


I will post it to somewhere better once it has been verified as working.

My work was based on what Ian Macdonald did here:


My source code is available here:

TWRP Source
Kernel source
Device tree

I'm finishing a write-up of what I did to create this image now. I'll post a link to that on this thread later today.
please make twrp for SM-T875 LTE MODEL
 
@bxlentpartyon So what can I say... unfortunately, no luck for you too. First of all, I'll also give it a try and make TWRP as T870 is my main tablet now, but neither my own built TWRP nor yours worked well so far. Getting the same "Blue screen" issue, that seems none of us knows how to fix. I will try to tweak some settings here and there, hopefully, we will be able to resolve this issue.
 

n0lan

Member
Apr 21, 2020
18
2
now that i have that out of the way. i decided to flash my tablet with this and i had a different issue. instead of a blue screen it was a black screen. i can see the top of twrp but the rest is cut off with blackness. i can get an image tomorrow. i hope that the image will help
 
now that i have that out of the way. i decided to flash my tablet with this and i had a different issue. instead of a blue screen it was a black screen. i can see the top of twrp but the rest is cut off with blackness. i can get an image tomorrow. i hope that the image will help
It really changes nothing. Blue screen appears after you turn the screen itself off and turn it on again back...
 
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RangeMachine

Member
Nov 4, 2021
5
4
So i found out that bug is probably related to pixelflinger rendering library which twrp uses, maybe someone who knows opengl will figure out.
 
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RangeMachine

Member
Nov 4, 2021
5
4
How did you actually find it out? Can you give some debug steps?
Welp i dont have any debug steps, but i compiled stock android recovery replacing bootable/recovery folder with some fixes and it worked just fine, so looking in source code i thought its mostly like related to minuitwrp/pixelfingler. Its really giving me headache reuploading each build to my device, but i hope i will find what casues that thing. In worst case we can modify stock recovery menu and make it using twrp features.
 
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Welp i dont have any debug steps, but i compiled stock android recovery replacing bootable/recovery folder with some fixes and it worked just fine, so looking in source code i thought its mostly like related to minuitwrp/pixelfingler. Its really giving me headache reuploading each build to my device, but i hope i will find what casues that thing. In worst case we can modify stock recovery menu and make it using twrp features.
You see, there is a method of debugging Android CODE via lldb while the device is running. Since every interface renderer is a process (like X11 in desktop Linux), you can start debugging it and maybe find a part of the code that may cause these issues. I'm a bit familiar with C++ and OpenGL, so I may try later. This investigation has gone really far... well
 
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RangeMachine

Member
Nov 4, 2021
5
4
My investigation continues: stock recovery using bit different DRM backend for rendering, you can see it on screenshot. I did not found any public sources containg that functions, good thing they are all exported from librecovery_ui.so. So i will probably try to use that precompiled library and call exported functions.
Безымянный.png
 
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n0lan

Member
Apr 21, 2020
18
2
Just guessing here, since TWRP does not use 3d rendering maybe the backend can use fbdev instead? Or is that not possible?
 

RangeMachine

Member
Nov 4, 2021
5
4
Just guessing here, since TWRP does not use 3d rendering maybe the backend can use fbdev instead? Or is that not possible?
Our devices dont have /dev/fb0 device which fbdev relies on. Not sure why even tho framebuffer driver compiled into kernel. I am on gts7l lte btw but pretty sure its same for wifi version.
 

n0lan

Member
Apr 21, 2020
18
2
Any further details you found? I am starting to get some hope now. Good luck with the search for the graphics issue. Sorry for being so edgy witc my whole development is dead rant
 

RangeMachine

Member
Nov 4, 2021
5
4
Any further details you found? I am starting to get some hope now. Good luck with the search for the graphics issue. Sorry for being so edgy witc my whole development is dead rant
Well no luck anymore :( I tried to use call Drm functions from librecovery_ui.so but no its just getting crashed, i will continue attempts anyway
 
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n0lan

Member
Apr 21, 2020
18
2
Well no luck anymore :( I tried to use call Drm functions from librecovery_ui.so but no its just getting crashed, i will continue attempts anyway
Does CWM still exist? I know that did not need a complex interface so maybe if it is updated still maybe try compiling that for the tab s7? The recovery does not matter as long as it can backup and flash custom roms
 

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  • 1
    So i found out that bug is probably related to pixelflinger rendering library which twrp uses, maybe someone who knows opengl will figure out.
    1
    So i found out that bug is probably related to pixelflinger rendering library which twrp uses, maybe someone who knows opengl will figure out.
    How did you actually find it out? Can you give some debug steps?
    1
    How did you actually find it out? Can you give some debug steps?
    Welp i dont have any debug steps, but i compiled stock android recovery replacing bootable/recovery folder with some fixes and it worked just fine, so looking in source code i thought its mostly like related to minuitwrp/pixelfingler. Its really giving me headache reuploading each build to my device, but i hope i will find what casues that thing. In worst case we can modify stock recovery menu and make it using twrp features.
    1
    Welp i dont have any debug steps, but i compiled stock android recovery replacing bootable/recovery folder with some fixes and it worked just fine, so looking in source code i thought its mostly like related to minuitwrp/pixelfingler. Its really giving me headache reuploading each build to my device, but i hope i will find what casues that thing. In worst case we can modify stock recovery menu and make it using twrp features.
    You see, there is a method of debugging Android CODE via lldb while the device is running. Since every interface renderer is a process (like X11 in desktop Linux), you can start debugging it and maybe find a part of the code that may cause these issues. I'm a bit familiar with C++ and OpenGL, so I may try later. This investigation has gone really far... well
    1
    My investigation continues: stock recovery using bit different DRM backend for rendering, you can see it on screenshot. I did not found any public sources containg that functions, good thing they are all exported from librecovery_ui.so. So i will probably try to use that precompiled library and call exported functions.
    Безымянный.png
  • 9
    This is my first thread of this kind, so bear with me if I'm not formatting it quite right.

    I've run a test build of TWRP 3 for the Galaxy Tab S7 Wifi (T870) against a customized version of the kernel that shipped with the T870OXM2BUC6 firmware. At this point, this is completely untested, as I do not currently have my tablet in a state where I can test it (I'm working on this).

    Here is a link to the recovery image on my Google Drive:


    I will post it to somewhere better once it has been verified as working.

    My work was based on what Ian Macdonald did here:


    My source code is available here:

    TWRP Source
    Kernel source
    Device tree

    I'm finishing a write-up of what I did to create this image now. I'll post a link to that on this thread later today.
    5
    Appreciate the effort, we do need devs here. But whats the actual point of twrp, when we have ZERO roms to flash.
    I did this partially as a learning exercise, to familiarize myself with the Android build process. I'm still obviously fairly new to the Android scene, but the biggest piece of TWRP that I hoped to utilize was the backup/restore functionality.

    Eventually I'm planning to try and install openSuSE on my tablet natively, and I wanted to be sure that I have solid backups, for when I eventually screw up and trash my device. I've learned through talking with jhill a bit that I'll probably get by just fine with just the stock firmware available to re-flash, but I wasn't entirely positive about that when I started working on this, and I figured I'd already burned the time building the kernel, so I might as well finish the job :p
    3
    Here is my write-up on how I did this.


    I tried to make it as complete as possible, but quite a bit of work went into this, so I'm sure I've left out some details. If you attempt this yourself, please let me know if/where you run into issues and I'll update the document accordingly.
    3
    Note that, once I have confirmation that my build process is sound, I'll be happy to try and perform builds for other devices in this family as well, as long as kernel sources are available.

    I've submitted a request to Samsung for the sources for the latest kernel for my device (T870XXU2BUF5). I'm not expecting a response until after the weekend, but I _think_ that they're obligated to provide the sources upon request.
    3
    There have been many people testing ianmacds build and trying to build twrp for the tab s7 but everybody had this blue screen issue which made the twrp screen unusable but you can use twrp from usb.
    Ianmacd and other users tried it with a slightly modified kernel from samsungs source
    Thanks for the explanation. From what I understood, nobody had really attempted a build for the T870 yet. I was unaware that it has been tried, but nobody has gotten it working. Judging from the fact that the TWRP source has been shown to be functional on the S7+, I'd assume that this is still a kernel issue, but knowing that certainly doesn't help anybody find what the actual issue is, haha.
    Welcome to the tab s7/+ dev community, I'm searching for more devs and custom stuff for our devices but sadly we aren't many, I've started trying to make Lineageos for the tab s7+ a while ago (my first from the ground up tree but I maintain ResurrectionRemix official for the OnePlus 6T since january) and I got further in small steps but since I'm stuck at this kernel issue since a month (I don't have much time atm but I'll try harder soon), the kernel doesn't want to load the fstab, I tried los17 and 18, asked many devs about this issue (jimbok77 mentioned a los18 init issue for the galaxy 20 series), this is my first device with dynamic partitions and my last samsung device was a samsung galaxy s5 mini exynos G800F, you can find more about my progress here Interest thread s7+ Lineage os and in the tab s7/+ development telegram chat, and you can find testers at telegram chat by ianmacd.

    My plans are to make a working lineageos and then postmarket os, ubuntu touch and jing os.
    The "custom ROMs" side of things is something I don't really have any knowledge about. To be honest, I don't have a ton of interest in going down that road, at least at the moment, as I don't really understand what benefits I would get from a custom ROM. From my point of view, I'm much more interested in getting "plain old Linux" running on the device, as that makes it far more powerful and useful, IMO.

    A big part of what I want to do with my device is to run gaming console emulators, and the whole added layer of complexity of needing to write a Java wrapper around an already-functional C program just to get it to run doesn't really appeal to me. Again, this could all be ignorance of the real possibilities on my part, but I'm just trying to give you an idea of where I'm coming from.

    Thanks again for the explanation of the current state of TWRP, and the introduction to some of the rest of what's going on out there!