Support Vulkan 1.1 on Raspberry Pi 4

[mzyy94]

TL;DR

I found a way to resolve Error: GraphicsAdapterNotFound bug on Raspberry Pi OS with Vulkan 1.1.

Related issues

• Iced on Raspberry PI 4 (almost working) #428
• feat: add support to ARM devices (and older hardware) #1160

Description

Since #1160, iced on Raspberry Pi runs only on top of OpenGL with "glow" feature flag.

Currently Raspberry Pi 4 is Vulkan 1.1 compliant. I think iced should work on Vulkan on Raspberry Pi 4.

Vulkan update: version 1.1 conformance for Raspberry Pi 4 - Raspberry Pi

Install Vulkan on Raspberry Pi 4 - Q-engineering

I installed Vulkan 1.1 on Raspberry Pi OS (32bit) following the above instructions, and then examples of wgpu work well.

glxinfo -B output

pi@raspberrypi:~ $ glxinfo -B
name of display: :0
display: :0  screen: 0
direct rendering: Yes
Extended renderer info (GLX_MESA_query_renderer):
    Vendor: Broadcom (0x14e4)
    Device: V3D 4.2 (0xffffffff)
    Version: 20.3.5
    Accelerated: yes
    Video memory: 3786MB
    Unified memory: yes
    Preferred profile: compat (0x2)
    Max core profile version: 0.0
    Max compat profile version: 2.1
    Max GLES1 profile version: 1.1
    Max GLES[23] profile version: 3.1
OpenGL vendor string: Broadcom
OpenGL renderer string: V3D 4.2
OpenGL version string: 2.1 Mesa 20.3.5 (git-42a4d76fcc)
OpenGL shading language version string: 1.20
OpenGL ES profile version string: OpenGL ES 3.1 Mesa 20.3.5 (git-42a4d76fcc)

OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.10
pi@raspberrypi:~ $ 

But, running iced example that depends on wgpu renderer (such as svg) fails with error message Error: GraphicsAdapterNotFound.
It should be expected to work correctly as good as wgpu example on Vulkan enabled platform, but it did not.

pi@raspberrypi:~/Desktop/iced $ WGPU_BACKEND=vulkan cargo run --package svg
   Compiling iced_wgpu v0.4.0 (/home/pi/Desktop/iced/wgpu)
   Compiling iced v0.3.0 (/home/pi/Desktop/iced)
   Compiling svg v0.1.0 (/home/pi/Desktop/iced/examples/svg)
    Finished dev [unoptimized + debuginfo] target(s) in 1m 25s
     Running `target/debug/svg`
WARNING: v3dv is neither a complete nor a conformant Vulkan implementation. Testing use only.
Error: GraphicsAdapterNotFound
pi@raspberrypi:~/Desktop/iced $

I wrote some code to find the bug and found that there is a problem in specifying a limits of wgpu::DeviceDescriptor.

diff --git a/wgpu/src/window/compositor.rs b/wgpu/src/window/compositor.rs
index 6feb795..64c5360 100644
--- a/wgpu/src/window/compositor.rs
+++ b/wgpu/src/window/compositor.rs
@@ -53,7 +53,7 @@ impl Compositor {
             .using_resolution(adapter.limits());

         #[cfg(not(target_arch = "wasm32"))]
-        let limits = wgpu::Limits::default();
+        let limits = wgpu::Limits::downlevel_defaults();

         let (device, queue) = adapter
             .request_device(

After changing the value of limits to wgpu::Limits::downlevel_defaults() shown in the patch above, the svg example worked good on Raspberry Pi 4.

There are still some issues with Vulkan backend on Raspberry Pi 4:

• The first frame is not drawn until some events occur
• Running with WGPU_BACKEND=gl env-var fails
• Glitches in some projects (e.g. game_of_life)

So, this is one way to support Vulkan 1.1 on a Raspberry Pi 4. But I don't have ideas to make better patch to source code.
Any ideas?

[hecrj]

Limits::downlevel_defaults sounds like a better default strategy. I have applied the patch in a53fa91. Thank you! 🙇

As to the game_of_life glitches, does it help if you disable the grid? What if you turn off the antialising field?

iced/examples/game_of_life/src/main.rs

Lines 23 to 30 in a53fa91

	GameOfLife::run(Settings {
	antialiasing: true,
	window: window::Settings {
	position: window::Position::Centered,
	..window::Settings::default()
	},
	..Settings::default()
	})

[mzyy94]

Superb patch! 🎉
The glitch continues regardless of the value of antialising. 😢

gameoflife.mp4