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Tab A7 (SM-T500) - Cannot boot custom kernel

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Hi everyone, as the title already says, I am having issues booting a custom kernel on my SM-T500. I have been able to flash agreenbhm's TWRP and boot that just fine, but that is using the prebuilt kernel. When I try to boot a custom kernel, OEM locking gets enabled out of nowhere and I have to reflash the stock ROM in order to be able to use the tab. I initially tried booting a WIP close-to-mainline kernel, so I assumed it's just an issue of the bootloader not liking the mainline kernel, but then I tried to flash a custom compiled downstream kernel and I got the same issue. Has anyone else ever had such an issue, even if it's on another device? Were you able to work around it? If yes, how? Thanks in advance for any answers.
 

lewmur

Senior Member
Apr 30, 2011
1,859
400
Hi everyone, as the title already says, I am having issues booting a custom kernel on my SM-T500. I have been able to flash agreenbhm's TWRP and boot that just fine, but that is using the prebuilt kernel. When I try to boot a custom kernel, OEM locking gets enabled out of nowhere and I have to reflash the stock ROM in order to be able to use the tab. I initially tried booting a WIP close-to-mainline kernel, so I assumed it's just an issue of the bootloader not liking the mainline kernel, but then I tried to flash a custom compiled downstream kernel and I got the same issue. Has anyone else ever had such an issue, even if it's on another device? Were you able to work around it? If yes, how? Thanks in advance for any answers.
What do you mean by "OEM locking"? Do you mean the FRP lock that you disable by enabling OEM mode in Developer options? That only requires you to enter the google account login and password to finish booting.
 
What do you mean by "OEM locking"? Do you mean the FRP lock that you disable by enabling OEM mode in Developer options? That only requires you to enter the google account login and password to finish booting.
OEM locking is indeed what I mean. Google Account is not a problem because I never log into it in the first place, and when I open up developer options OEM unlocking is enabled and grayed out with a "Bootloader is already unlocked" message.
 

lewmur

Senior Member
Apr 30, 2011
1,859
400
OEM locking is indeed what I mean. Google Account is not a problem because I never log into it in the first place, and when I open up developer options OEM unlocking is enabled and grayed out with a "Bootloader is already unlocked" message.
If you don't have a google account setup on the tablet, the FRP is irrelevant. So what's the problem? BTW, the FRP lock and the bootloader lock are two entirely different things. One has nothing to do with the other. The FRP lock has been around long before Samsung started locking the bootloader on non-carrier tablets.
 
The problem is that, even when the bootloader is unlocked, the tablet simply won't accept a custom kernel. If you want to know why I believe OEM lock is at fault here, first take a look at the download mode screen **before** flashing a custom kernel:
IMG_20210727_113457.jpg

Then, after flashing a custom kernel:
IMG_20210721_153947.jpg

(sorry for the below average picture quality, especially on the last one)

After flashing the custom kernel, "Current Binary" goes from "Samsung Official" to "Custom", and **OEM lock** goes from Off to **On**, and every time I restart the tablet it will go straight to download mode until I reflash the stock firmware.
 

lewmur

Senior Member
Apr 30, 2011
1,859
400
The problem is that, even when the bootloader is unlocked, the tablet simply won't accept a custom kernel. If you want to know why I believe OEM lock is at fault here, first take a look at the download mode screen **before** flashing a custom kernel:
View attachment 5371623
Then, after flashing a custom kernel:
View attachment 5371625
(sorry for the below average picture quality, especially on the last one)

After flashing the custom kernel, "Current Binary" goes from "Samsung Official" to "Custom", and **OEM lock** goes from Off to **On**, and every time I restart the tablet it will go straight to download mode until I reflash the stock firmware.
If you ever get the tablet to boot, and look in Develper options, you find the setting for OEM is enabled and greyed out so you can't change it. IOW, OEM lock is ON and your custom ROM has no Factory Reset Protection. If someone steels the tablet, they can get past the lock screen simply by doing a factory reset. There is some other reason you are boot looping.
 

lewmur

Senior Member
Apr 30, 2011
1,859
400
I think that is controlled by the vbmeta.img. That's normally the first step in flashing a custom ROM. I copied the following from the thread on installing LOS 18.1.

  1. Boot into download mode and flash "vbmeta_disabled_R.tar" via Odin in the "Userdata" slot to disable verified boot. This will wipe your device again.
 
Last edited:

xAriana

Member
May 12, 2018
24
0
I think that is controlled by the vbmeta.img. That's normally the first step in flashing a custom ROM. I copied the following from the thread on installing LOS 18.1.

  1. Boot into download mode and flash "vbmeta_disabled_R.tar" via Odin in the "Userdata" slot to disable verified boot. This will wipe your device again.
did u ever solve this