(OpenGL) Bios renders only a black screen

[orbea]

Description

With OpenGL the bios now renders as only black. Software is unaffected and I am not able to testing vulkan. Sound still works.

Expected behavior

The bios should render.

Actual behavior

The bios renders as a black screen with sound.

Steps to reproduce the bug

1. Build beetle-psx-libtetro with opengl
2. Start beetle-psx-librtetro with opengl and the bios skip hack off.
3. Observe a black screen instead of the bios.

Bisect Results

Previously unaffected beetle-psx-libretro commits either do not work at all anymore or also show this issue. Older RetroArch releases also seem affected. I will try checking other programs next like mesa.

Version/Commit

• RetroArch: 1.7.1
• beetle-psx-libretro: 063eec6

Environment information

• OS: Slackware64-current
• Compiler: gcc-7.3.0

[ghost]

Does the content render normally after the BIOS? What about if you take a screenshot during the BIOS boot (try with both GPU screenshot on and off)? Do you see any video in the screenshot then?

[orbea]

Content did seem to render before making this issue, but I must of been testing something wrong since it doesn't render now either. Taking screenshots with GPU screenshot on or off just shows a black screen.

[orbea]

No improvement with the llvmpipe or with a fresh config, but apitrace reveals lots of issues...

http://ks392457.kimsufi.com/orbea/stuff/trace/retroarch_beetle_psx_blackscreen.trace.xz
apitrace log - https://pastebin.com/fsU7jejG

[orbea]

Its getting worse for no known reason...now it just crashes.

Log - https://pastebin.com/fucUctse
When loading content with -L the backtrace changes - https://pastebin.com/VDM5WMuk

[orbea]

Clearing the mesa shader cache files resolved the crash and now its back to a black screen....

[ghost]

tried with GL_DEBUG and/or ASAN?

[orbea]

Not yet, its a change in mesa that caused this. I will bisect sometime today.

[orbea]

First bad commit.

a0c8b49284efe736849c0a45920ad0a1bbd8d93d is the first bad commit
commit a0c8b49284efe736849c0a45920ad0a1bbd8d93d
Author: Marek Olšák <[email protected]>
Date:   Wed Feb 14 20:13:40 2018 +0100

    mesa: enable OpenGL 3.1 with ARB_compatibility
    
    Tested-by: Dieter Nützel <[email protected]>
    Reviewed-by: Brian Paul <[email protected]>

:040000 040000 e77355f4d5979f42b5e8f55dd6c6ea62cba32ff3 24f0fe1b3e5f9d1daa801a706299f0115f9d8f2d M	docs
:040000 040000 89d6cc6fe13b05f4625fb48abbb94050f0cb5c96 3b91e5c0091caf1426b09568846f8f2b3bc64803 M	src

https://github.com/mesa3d/mesa/commit/a0c8b49284efe736849c0a45920ad0a1bbd8d93d

[orbea]

My understanding is that there might be something in beetle-psx or maybe libretro making assumptions about GL versions which are no longer correct after that commit.

[orbea]

This can be worked around by exporting MESA_GL_VERSION_OVERRIDE to at least 3.2 where 3.1 will display garbage and 3.0 doesn't boot the core.

For example.

export MESA_GL_VERSION_OVERRIDE=3.2

or

export MESA_GL_VERSION_OVERRIDE=4.5

[orbea]

This also fixes it.

diff --git a/libretro-common/glsm/glsm.c b/libretro-common/glsm/glsm.c
index ab8c562..0f01a27 100644
--- a/libretro-common/glsm/glsm.c
+++ b/libretro-common/glsm/glsm.c
@@ -2207,7 +2207,7 @@ static bool glsm_state_ctx_init(void *data)
 #ifdef CORE
    hw_render.context_type       = RETRO_HW_CONTEXT_OPENGL_CORE;
    hw_render.version_major      = 3;
-   hw_render.version_minor      = 1;
+   hw_render.version_minor      = 3;
 #else
    hw_render.context_type       = RETRO_HW_CONTEXT_OPENGL;
 #endif

I think libretro-common probably shouldn't request a 3.1 core context?

An excerpt from #nouveau which was kind enough to help debug this.

11:57 <imirkin_> ok. so ACTUALLY ... i think this is a mesa bug.
11:58 <imirkin_> we probably see GLX_CONTEXT_PROFILE_MASK_ARB + GLX_CONTEXT_CORE_PROFILE_BIT_ARB and happily return the 3.1 compat context.
11:58 <imirkin_> we should not do that.
11:58 <karolherbst> imirkin_: you mean they request core + 3.1?
11:58 <karolherbst> and then we screw up?
11:58 <imirkin_> it's also a psx core bug, in that it should not be asking for a 3.1 core context, since that's not a thing.
11:58 <imirkin_> yes
11:59 <imirkin_> i haven't looked at the code
11:59 <imirkin_> but this seems plausible.
11:59 <karolherbst> well it makes sense

[orbea]

This seems to be really a mesa + libretro-common bug.

As far as libretro-common goes, it probably should not be hardcoded to 3.1 and should use the highest available core context.

retroarch --verbose

[INFO] [GLX]: Using Xinerama on screen #0.
[INFO] [GLX]: X = 0, Y = 0, W = 1680, H = 1050.
[INFO] [GLX]: Using windowed fullscreen.
[INFO] [GLX]: Found swap function: glXSwapIntervalMESA.
[INFO] [GLX]: glXSwapInterval(1)
[INFO] [GL]: Vendor: nouveau, Renderer: NVF1.
[INFO] [GL]: Version: 3.1 Mesa 18.1.0-devel (git-163a29099a).

$ glxinfo | grep Core
OpenGL core profile version string: 4.5 (Core Profile) Mesa 18.1.0-devel (git-163a29099a)

[ghost]

How would you know what the highest available is?

[orbea]

I'm not sure yet, maybe I am misunderstanding the logs and its reporting the minimum available version and not the given context?

[orbea]

I know dolphin-emu reports that I have OpenGL 4.5 exposed correctly, maybe their code could offer clues?

[rz5]

@Themaister - Mind taking a quick peek? Noveau devs suggest that requesting a core context in addition to specifying a 3.1 version number is an error.

[simias]

In the original rust code I request a CORE 3.3 context, I'm not sure why or when the requirement got lowered in beetle.

[orbea]

@rz5 I missed you on irc so I will reply here.

My understanding is that there are two issues here.

1. beetle-psx is requesting a 3.1 context, getting one and then not liking it.
2. mesa is going along with this even when it should have good reasons to not.

This is a result of there being a lot of confusion with 3.1 contexts and any application that wants a real core profile should request at least 3.2.

This is also a general mesa issue and not just nouveau. I confirmed already that it already occurs with the llvmpipe too, it would be helpful if anyone that has either mesa and amd or intel could also test this with the mesa git master.

[rz5]

@twinaphex - Based on @simias's observation about the Rustation GL renderer being 3.3, then I propose we bump glsm.c's request up to at least match it since it's what beetle-psx's GL renderer is based on. This should be done at least after more info on this bug is found.

[orbea]

I've created a PR to raise it to 3.3 again. I'm not there is much more to discuss as far as beetle-psx is concerned.