Screen scrambled on Clip Zip with RB 3.15

[sansalex]

Hello there, this is Alex, happy owner of a Sansa Clip Zip mounting RockBox since years
Unfortunately with 3.15 and 3.14 I have the following issue: at boot, the main menu screen is all scrambled (see attached photo).
If I wait until the screen turns off to black, when I turn it on again with the power button, the graphics are perfect.
This happens with the release candidate and the latest developer build too. This doesn't occur with 3.13!
Is there any way you could help me? Thanks a lot 

[Bilgus]

is this with a theme or totally stock? have you tried deleting the whole rockbox directory?

I have changed some display clocks since 3.14 IIRC but out of quite a few I have yet to see it look like
that unless there is memory corruption

[sansalex]

There is no theme but the default one. I checked the failsafe theme, same thing. Also tried to delete RockBox folder and reinstall from scratch, same problem.
Please note that, as already said, when the screen turns off and then again on, there are no longer issues. The issue is at boot.

[Bilgus]

hmm insanely hard to diagnose do you have the latest bootloader as well?

[Bilgus]

does it only clear up after screen off / on or will it clear up if you run an app maybe one of the lua ones?

[sansalex]

Yes, I have the latest bootloader as well.
Tried to install bootloader from RockBox Utility with the original firmware both .18 and .21 but same behaviour.
I can confirm running apps doesn't resolve, it resolves only after screen off/on and doesn't occur again, until reboot.

[Bilgus]

Ok, I have compiled a version for you that turns the screen off and back on at initialization lets see if that works

http://www.mediafire.com/file/1322rd061hixj4h/ClipZip_Corrupted_display_2-27-20_rockbox-full.zip

[sansalex]

Thank you so much, this solved the issue!
However, booting takes a huge time: previously 2-3 seconds and now 37 seconds, why? 

[Bilgus]

I'm guessing now it has to wait for the screen to become available so lets try a different method

I think the variable is_enabled is in an indeterminate state so lets try setting its value explicitly
http://www.mediafire.com/file/9a3mhc8r0ndwipw/ClipZip_Corrupted_displayV2_2-27-20_rockbox-full.zip

and if that version doesn't work I have another idea which is pretty much the same as the original that takes 37s to boot but does it later in the boot process
http://www.mediafire.com/file/96wqqqyrprdzc3v/ClipZip_Corrupted_displayV3_2-27-20_rockbox-full.zip

[sansalex]

Here are the results (not so good, V1 was better):

V2: 41 seconds. The screen turns off after the boot splash and turns on when the system is ready. Turning it on manually while waiting, will result in a new automatic turn off.
V3: 43 seconds. Same behaviour.

Thanks for your time!

[Bilgus]

hmm rather odd lets try a version with no changes to rule everything else out

http://www.mediafire.com/file/3ymlzaj5s6wta3g/ClipZip_HEAD_2-27-20_rockbox-full.zip

[Bilgus]

Probably the battery life 'improvements' strike again

http://forums.rockbox.org/index.php/topic,48549.msg229832.html#msg229832

@saratoga

Going into the debug menu and manually boosting hard locks the player, so I suppose that is the problem.

Edit:  1 time hard locked, the next corrupted the display, and the third worked correctly but crashed shortly there after when I tried to play a song.

Maybe a better approach would be to confirm that frequency scaling is really working, and then try to adjust PCLK? I think 120MHz is probably far outside of the device spec.

[Bilgus]

when you get a chance try this version with power saving disabled and see if that improves the display
this build is older somewhere after 3.14 was released but before 3.15

http://www.mediafire.com/file/ncva10187km6za3/clipzip_powersave_12-5-17_rockbox-full.zip

[sansalex]

Probably the battery life 'improvements' strike again

This is very interesting about the probable root cause of the problem.
Anyway, I must apologize for this inconvenience: after realizing I was having long boot times with any RockBox version, I searched everywhere and found that folders ##MUSIC# and ##PORT# contained corrupted files which I was unable to backup or delete and were freezing my PC, maybe due to the many tests I did on my ClipZip 
I decided to format the unit and reinstall all on the empty memory... magically the boot time is good again, and I can confirm that the very first build you provided (V1) is working flawlessly with a boot time of 2 seconds!
If you want to proceed further to find a "real" solution to the bug, I'm available to test your new builds.
I'm just wondering this: when 3.16 will be released, will I have again the screen problem or a fix (temporary/permanent) will be included?

ps: now testing the power saving one

Thanks again.

[sansalex]

when you get a chance try this version with power saving disabled and see if that improves the display
this build is older somewhere after 3.14 was released but before 3.15

This is an update to the post above. Nope, this build still has the scrambled screen.