# Enable graphics acceleration on Raspberry Pi 4B

###### tags: `Raspberry Pi` `Linux Kernel` `DRM` `GPU`

**Note:** This is a test report, not an official solution yet.

Thanks to the ecosystem's effort. The pure Linux mainline kernel (not RPi OS kernel) works well on Raspberry Pi 4B 4GB, which I have on hands. System boots up, gets into GNOME desktop environment, has the VC4 DRM driver, connects to the HDMI (including HDMI audio). The ethernet & WiFi work as well.

It is **"almost"** good to be a normal computer for daily usage now. Why it is **"almost"**??? Because, it lacks the driver to support the V3D GPU on BCM2711, which will make the UI acting more smoothly.

Stefan has listed the supporting status at "[Upstream Raspberry Pi 4 B support](https://github.com/lategoodbye/rpi-zero/issues/43)".

In Febuaraury of this year, Nicolas sent out the patch series "[RFC/PATCH,00/11] [Raspberry PI 4 V3D enablement](https://patchwork.kernel.org/project/linux-arm-kernel/cover/[e-mail]/)".
Following that, a few days later, there is the new patch series "[v3,00/15] [Raspberry PI 4 V3D enablement](https://patchwork.kernel.org/project/linux-arm-kernel/cover/[e-mail]/)".

Earlier this month, I participated in #EndlessOrangeWeek, a program where the entire Endless team engages in projects designed to grow our collective learning related to our skills, work and mission. I chose this topic to test the GPU on Raspberry Pi 4B.

## Build the kernel
I applied the v3 patch series based on [mainline Linux kernel at tags/v5.15](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/?h=v5.15). Then tested the modified kernel with [Ubuntu 21.10 RPi 4B image](https://ubuntu.com/download/raspberry-pi) by replacing the kernel, device tree blob and initrd.

#### Applied cleanly:
* [v3,01/15] [dt-bindings: soc: bcm: bcm2835-pm: Convert bindings to DT schema](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,02/15] [dt-bindings: soc: bcm: bcm2835-pm: Introduce reg-names](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,03/15] [dt-bindings: soc: bcm: bcm2835-pm: Add support for bcm2711](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,04/15] [ARM: dts: bcm2835/bcm2711: Introduce reg-names in watchdog node](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,05/15] [ARM: dts: bcm2711: Use proper compatible in PM/Watchdog node](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,06/15] [mfd: bcm2835-pm: Use 'reg-names' to get resources](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,07/15] [mfd: bcm2835-pm: Add support for BCM2711](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,08/15] [soc: bcm: bcm2835-power: Add support for BCM2711's RPiVid ASB](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,09/15] [soc: bcm: bcm2835-power: Bypass power_on/off() calls](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,10/15] [dt-bindings: gpu: v3d: Add BCM2711's compatible](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,13/15] [ARM: dts: bcm2711: Enable V3D](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)

#### Fixed conflict and applied:

* [v3,11/15] [drm/v3d: Get rid of pm code](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,12/15] [drm/v3d: Add support for bcm2711](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)

#### Just the build config:

* [v3,14/15] [ARM: configs: Enable DRM_V3D](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)
* [v3,15/15] [arm64: config: Enable DRM_V3D](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/)

Here is my test repository: https://github.com/starnight/linux/tree/v3d-5.15
The kernel is built as aarch64 architecture with enabled `CONFIG_DRM_V3D` and `CONFIG_DRM_VC4`.
Then, install the kernel, initrd and device tree blob into the boot partion.

## Prepare the system boot path
Edit the **config.txt** to use the modified kernel and initrd.

kernel=vmlinux-5.15.0+
initramfs initrd.imag-5.15.0+ followkernel

Comment all of the `dtoverlay` in **config.txt** as well. I use the device tree blob from the patched kernel for this test.

Insert the SD card to Rasperry Pi 4B and power on!

## Check the V3D
Seems the kernel initialized the V3D GPU.

$ dmesg | grep v3d
[ 2.274145] [drm] Initialized v3d 1.0.0 20180419 for fec00000.gpu on minor 0

The device tree has the GPU node.

$ cat /proc/device-tree/scb/gpu@7ec00000/compatible
brcm,bcm2711-v3d

Mesa shows "`GL_RENDERER: V3D 4.2`"!

$ es2_info
EGL_VERSION: 1.4
EGL_VENDOR: Mesa Project
EGL_EXTENSIONS:
EGL_ANDROID_blob_cache, EGL_CHROMIUM_sync_control, EGL_EXT_buffer_age,
EGL_EXT_image_dma_buf_import, EGL_EXT_image_dma_buf_import_modifiers,
EGL_EXT_swap_buffers_with_damage, EGL_KHR_cl_event2,
EGL_KHR_config_attribs, EGL_KHR_create_context,
EGL_KHR_create_context_no_error, EGL_KHR_fence_sync,
EGL_KHR_get_all_proc_addresses, EGL_KHR_gl_colorspace,
EGL_KHR_gl_renderbuffer_image, EGL_KHR_gl_texture_2D_image,
EGL_KHR_gl_texture_3D_image, EGL_KHR_gl_texture_cubemap_image,
EGL_KHR_image, EGL_KHR_image_base, EGL_KHR_image_pixmap,
EGL_KHR_no_config_context, EGL_KHR_reusable_sync,
EGL_KHR_surfaceless_context, EGL_KHR_swap_buffers_with_damage,
EGL_EXT_pixel_format_float, EGL_KHR_wait_sync,
EGL_MESA_configless_context, EGL_MESA_drm_image,
EGL_MESA_image_dma_buf_export, EGL_MESA_query_driver,
EGL_NOK_texture_from_pixmap
EGL_CLIENT_APIS: OpenGL OpenGL_ES
GL_VERSION: OpenGL ES 3.1 Mesa 21.2.2
GL_RENDERER: V3D 4.2
GL_EXTENSIONS:
GL_EXT_blend_minmax, GL_EXT_multi_draw_arrays,
GL_EXT_texture_compression_s3tc, GL_EXT_texture_compression_dxt1,
GL_EXT_texture_format_BGRA8888, GL_OES_compressed_ETC1_RGB8_texture,
GL_OES_depth24, GL_OES_element_index_uint, GL_OES_fbo_render_mipmap,
GL_OES_mapbuffer, GL_OES_rgb8_rgba8, GL_OES_standard_derivatives,
GL_OES_stencil8, GL_OES_texture_3D, GL_OES_texture_float,
GL_OES_texture_half_float, GL_OES_texture_half_float_linear,
GL_OES_texture_npot, GL_OES_vertex_half_float, GL_EXT_draw_instanced,
GL_EXT_texture_sRGB_decode, GL_OES_EGL_image, GL_OES_depth_texture,
GL_OES_packed_depth_stencil, GL_EXT_texture_type_2_10_10_10_REV,
GL_OES_get_program_binary, GL_APPLE_texture_max_level,
GL_EXT_discard_framebuffer, GL_EXT_read_format_bgra, GL_EXT_frag_depth,
GL_NV_fbo_color_attachments, GL_OES_EGL_image_external, GL_OES_EGL_sync,
GL_OES_vertex_array_object, GL_ANGLE_pack_reverse_row_order,
GL_ANGLE_texture_compression_dxt3, GL_ANGLE_texture_compression_dxt5,
GL_EXT_occlusion_query_boolean, GL_EXT_texture_rg, GL_EXT_unpack_subimage,
GL_NV_draw_buffers, GL_NV_read_buffer, GL_NV_read_depth,
GL_NV_read_depth_stencil, GL_NV_read_stencil, GL_EXT_draw_buffers,
GL_EXT_map_buffer_range, GL_KHR_debug,
GL_KHR_texture_compression_astc_ldr, GL_NV_pixel_buffer_object,
GL_OES_depth_texture_cube_map, GL_OES_required_internalformat,
GL_OES_surfaceless_context, GL_EXT_color_buffer_float,
GL_EXT_sRGB_write_control, GL_EXT_separate_shader_objects,
GL_EXT_shader_implicit_conversions, GL_EXT_shader_integer_mix,
GL_EXT_base_instance, GL_EXT_compressed_ETC1_RGB8_sub_texture,
GL_EXT_draw_elements_base_vertex, GL_EXT_primitive_bounding_box,
GL_EXT_shader_io_blocks, GL_EXT_texture_border_clamp,
GL_KHR_context_flush_control, GL_NV_image_formats,
GL_OES_draw_elements_base_vertex, GL_OES_primitive_bounding_box,
GL_OES_shader_io_blocks, GL_OES_texture_border_clamp,
GL_OES_texture_stencil8, GL_OES_texture_storage_multisample_2d_array,
GL_EXT_buffer_storage, GL_EXT_float_blend, GL_EXT_geometry_point_size,
GL_EXT_geometry_shader, GL_KHR_no_error,
GL_KHR_texture_compression_astc_sliced_3d, GL_OES_EGL_image_external_essl3,
GL_OES_geometry_point_size, GL_OES_geometry_shader,
GL_OES_shader_image_atomic, GL_EXT_texture_compression_s3tc_srgb,
GL_MESA_shader_integer_functions, GL_KHR_parallel_shader_compile,
GL_EXT_EGL_image_storage, GL_MESA_framebuffer_flip_y,
GL_EXT_texture_query_lod, GL_MESA_bgra

Then, test it with `es2gears`.
But, the UI becomes frozen some times and the kernel shows the error "`flip_done timed out`":

[drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
[drm:drm_atomic_helper_wait_for_flip_done] *ERROR* [CRTC:68:crtc-3] flip_done timed out
[drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CRTC:68:crtc-3] commit wait timed out
[drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
vc4-drm gpu: [drm] *ERROR* Timed out waiting for commit

I notice that this error happens when ever applications touch GL related things with ont only patched kernel, but also the pure mainline kernel. So, I filed this bug to upstream as "[VC4 DRM waiting for flip down makes UI freeze a while with kernel 5.15](https://bugzilla.kernel.org/show_bug.cgi?id=214991)".

I found this error is related to the commits:

* [f3c420fe19f8 ("drm/vc4: kms: Convert to atomic helpers")](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f3c420fe19f8cc39adf379365decf63167596dc3)
* [82faa3276012 ("drm/vc4: kms: Remove async modeset semaphore")](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=82faa3276012d272d930026e7666d978ef2c6fef)

So, I reverted these two commits as a workaround. After this, the "flip_done timed out" error does not appear again.

Okay! Let's play the 3D game [OpenArena](http://openarena.ws/smfnews.php) for test!!!

It works better than without GPU! However, the resolution has to be downgraded to 1024x576 for example. Otherwise, the UI response will be so lag.

## Recap

* The v5.15 and latest mainline kernel with fixed conflict patches and fixed "flip_done timed out" bug can play the v3d gpu on Ubuntu 21.10. So, the device tree part & binding in the patch series are okay.
* However, the patch [v3,11/15] [drm/v3d: Get rid of pm code](https://patchwork.kernel.org/project/linux-arm-kernel/patch/[e-mail]/) makes me thinking: Is there any better way to do that. And, this might be why upstream did not merge the patch series.
* Have to find out why the v3d gpu of modified kernel works with Ubuntu, but does not work with other distros, like Endless OS. Problems in mesa, libdrm, Xorg/Wayland or any other packages?
* Mesa: Installed the same Mesa 21.2.2-1ubuntu1
* libdrm: Installed the same libdrm 2.4.107-8ubuntu1
* Xorg/Wayland (both run with Wayland):
* Ubuntu Impish has xwayland 2:1.20.13-1ubuntu1
* Endless OS has xwayland 2:1.20.11-1endless1bem1