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

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bxlentpartyon

Member
Aug 19, 2020
47
46
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.
 

bxlentpartyon

Member
Aug 19, 2020
47
46
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.
 

bxlentpartyon

Member
Aug 19, 2020
47
46
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.
 

Bushcat

Member
Nov 14, 2018
25
1
22
Samsung Galaxy S5 Mini
OnePlus 6T
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.
when I requested the sources for my T970 it took over a month and I requested it 3 times.
 
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Bushcat

Member
Nov 14, 2018
25
1
22
Samsung Galaxy S5 Mini
OnePlus 6T
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.
I doubt that it'll work, I tried it a while ago (I didn't test it myself) with added firmware files, updated kernel and device tree stuff and I used a very custom upstreamed samsung sm8250 common kernel which I had good experience with but it had the same issue, your commits are mostly updates for the twrp a11 source and new kernel source, so the differrences from my build and yours are that I have a more custom and upstreamed kernel with firmware but you used the a11 twrp source (which manifest wasn't available for me when I made it).
 
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bxlentpartyon

Member
Aug 19, 2020
47
46
I used a very custom upstreamed samsung sm8250 common kernel which I had good experience with but it had the same issue
Not sure what issue you're talking about here. The guy whose process I copied didn't seem to have problems, or at least not many significant ones.

If you did this same thing with a "very custom" kernel and were not successful, my instinct would be that the kernel was "too custom." The whole idea behind my method of customizing my kernel was to minimize the differences between what I built, and the kernel that Samsung shipped, which is known to be functional.
 
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bxlentpartyon

Member
Aug 19, 2020
47
46
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
 

bs3pro

Senior Member
Jul 24, 2020
323
71
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
Keep up the good work! Not complaining, just wish we had a couple devs making aosp. Thanks
 
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Bushcat

Member
Nov 14, 2018
25
1
22
Samsung Galaxy S5 Mini
OnePlus 6T
Not sure what issue you're talking about here. The guy whose process I copied didn't seem to have problems, or at least not many significant ones.

If you did this same thing with a "very custom" kernel and were not successful, my instinct would be that the kernel was "too custom." The whole idea behind my method of customizing my kernel was to minimize the differences between what I built, and the kernel that Samsung shipped, which is known to be functional.
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, I wanted to try a differrent kernel because samsungs kernel source can be ****ty sometimes so I tried an upstreamed lineageos samsung sm8250 common kernel (which I'm also using for my galaxy tab s7+ TWRP and PBRP builds and it's working well there) but it had the same issue. The Tab S7+ also has a small display issue in twrp but it's still usable, when hitting some ubttons in twrp you can sometimes see a small flickering stripe at the top. In twrp it's hard to notice but in PBRP this issue was very annoying because it happenned much mnore often and longer, it got very bad when you turn off and on the display in recovery, I was able to lower the glitches with some screen values like timeout but I wasn't able to fix this issue.


5467927950235120033_121.jpg
 
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Bushcat

Member
Nov 14, 2018
25
1
22
Samsung Galaxy S5 Mini
OnePlus 6T
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
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.

Mod Edit: TG links removed as per XDA Telegram Chat Rules.
 
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bxlentpartyon

Member
Aug 19, 2020
47
46
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!
 

bxlentpartyon

Member
Aug 19, 2020
47
46
I doubt that it'll work, I tried it a while ago (I didn't test it myself) with added firmware files, updated kernel and device tree stuff and I used a very custom upstreamed samsung sm8250 common kernel which I had good experience with but it had the same issue
Arrrgh, you were right. I finally spent the time to fully root my tablet and get my TWRP build installed, but the end result was exactly like the screen pic you posted. You can see the top of the screen, but everything else is just blue. Being new to TWRP, I didn't know how to pull the log at the time to see if there were any obvious errors in it, and I've already flashed back to stock recovery at this point.

I'll give this another go sometime later this week, or over the weekend, and see if I can learn anything else.

If anyone has some basic TWRP debugging tips that would be helpful. From what I've seen the number one option is:

abd pull /tmp/recovery.log

But I'm not sure if that is still valid, or if there are other things that can be done.
 

bxlentpartyon

Member
Aug 19, 2020
47
46
Scratch some of what I said above. I determined that:

/cache/recovery/last_kernel.log

Contains the log buffer from TWRP booting my custom kernel, and:

/cache/recovery/last_kmsg*

Contain log buffers from regular kernel boots. I'm combing through these looking for any interesting differences now, but there's obviously a lot to comb through, and it takes some effort to determine what is expected to be different due to config differences, and what might actually be important.

At least I've got something interesting to stare at for a little while.
 

Jerry12798

Senior Member
Scratch some of what I said above. I determined that:

/cache/recovery/last_kernel.log

Contains the log buffer from TWRP booting my custom kernel, and:

/cache/recovery/last_kmsg*

Contain log buffers from regular kernel boots. I'm combing through these looking for any interesting differences now, but there's obviously a lot to comb through, and it takes some effort to determine what is expected to be different due to config differences, and what might actually be important.

At least I've got something interesting to stare at for a little while.
Anything you need help with? Unfortunately I'm only a web developer so I don't think my Pyhton, CSS, or HTML knowledge would help much in the development of custom recovery but if there's anything we can do I'm happy to contribute.
 
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Vntnox

Senior Member
Feb 12, 2017
157
51
London
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.
I put a lot of effort and tried hard to find out the issue source. Mixed and compiled many different dtbos but every attempt gave me exactly the same result. I used almost stock sammy kernel and my highly modified Amnesty build.
 
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bxlentpartyon

Member
Aug 19, 2020
47
46
Anything you need help with? Unfortunately I'm only a web developer so I don't think my Pyhton, CSS, or HTML knowledge would help much in the development of custom recovery but if there's anything we can do I'm happy to contribute.
Unfortunately I barely know enough about Android/TWRP to even know what to ask for help with, haha. If you want to pitch in, I'd encourage you to get your feet wet and try to run a TWRP build and see if you can reach the same point that others have gotten to (i.e. blue screen). You can use the guide I posted above to attempt that. I'll be glad to help with any questions you have along the way.

From there, it seems like it's basically anybody's game at this point. Apply whatever knowledge you have to see if you can make progress on the current issue!
 

Jerry12798

Senior Member
Unfortunately I barely know enough about Android/TWRP to even know what to ask for help with, haha. If you want to pitch in, I'd encourage you to get your feet wet and try to run a TWRP build and see if you can reach the same point that others have gotten to (i.e. blue screen). You can use the guide I posted above to attempt that. I'll be glad to help with any questions you have along the way.

From there, it seems like it's basically anybody's game at this point. Apply whatever knowledge you have to see if you can make progress on the current issue!
Yea I've tried it but blue screened too. I know a few different devices I've messed around with before has had weird screen issues (flickering, off colors, etc) in TWRP.. I don't know if they had the sames issue we are or not but it seems probable.
 

bxlentpartyon

Member
Aug 19, 2020
47
46
I put a lot of effort and tried hard to find out the issue source. Mixed and compiled many different dtbos but every attempt gave me exactly the same result. I used almost stock sammy kernel and my highly modified Amnesty build.
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.
 
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  • 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
    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!
    2
    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
    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.

    Mod Edit: TG links removed as per XDA Telegram Chat Rules.