Update Tyr Upstream Development Process

Currently the upstream development process for Tyr suggests that a
developer could open a merge request for review and discussion in
the panfrost-linux repository on Freedesktop GitLab.

While merge requests can still be a useful collaboration tool, other DRM
developers might not be reading those merge requests, so to be absolutely
clear, just direct new upstream contributions to the mailing lists.

Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>

Author: deborahbrouwer

src/Tyr-GPU-Driver.md

@@ -2,17 +2,13 @@
 
 ## What is Tyr?
 
-Tyr is a new Rust-based DRM driver for CSF-based Arm Mali GPUs. It is a port of
-Panthor — a driver written in C for the same hardware — and written as a joint
-effort between Collabora, Arm and Google engineers.
+Tyr is a new Rust-based DRM driver for CSF-based Arm Mali GPUs. It is a Rust
+reimplementation of Panthor — a driver written in C for the same hardware —
+developed jointly by Collabora, Arm, and Google engineers.
 
 Tyr aims to eventually implement the same userspace API offered by Panthor for
-compatibility reasons, so that it can be used as a drop-in replacement in our
-Vulkan driver, called
-[PanVK](https://gitlab.freedesktop.org/mesa/mesa/-/tree/main/src/panfrost/vulkan?ref_type=heads).
-In any case, we foresee Panthor being used — and of course supported — for a
-relatively long time, as it is a mature driver with a large adoption in the
-ecosystem. It will probably take a couple of years for Tyr to fully pick up.
+compatibility reasons, so that it can be used as a drop-in replacement by the
+[PanVK](https://gitlab.freedesktop.org/mesa/mesa/-/tree/main/src/panfrost/vulkan?ref_type=heads) Vulkan driver.
 
 ## Where is Tyr developed?
 
@@ -22,76 +18,42 @@ Tyr is developed both upstream and downstream.
 
 The initial skeleton of the Tyr driver is now [upstream](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/tyr). Submissions against
 the upstream Tyr driver should go to the [`dri-devel`](https://lore.kernel.org/dri-devel/)
-and [`rust-for-linux`](https://lore.kernel.org/rust-for-linux/) mailing lists. If the
-submission is larger and/or needs to be pre-reviewed, open a merge request
-against the
-[`tyr-for-upstream`](https://gitlab.freedesktop.org/panfrost/linux/-/tree/tyr-for-upstream)
-branch in the [`panfrost/linux`](https://gitlab.freedesktop.org/panfrost/linux)
-repository.
+and [`rust-for-linux`](https://lore.kernel.org/rust-for-linux/) mailing lists.
+
+Tyr commits should usually apply cleanly to [`drm-rust-next`](https://gitlab.freedesktop.org/drm/rust/kernel.git).
 
 ### Downstream
 
-A more complete implementation of the Tyr driver is also available in the
+Patches that are close to going upstream are collected for convenience in the
+[`tyr-for-upstream`](https://gitlab.freedesktop.org/panfrost/linux/-/tree/tyr-for-upstream) branch.
+
+A work-in-progress implementation of the full Tyr driver is also available in the
 [`tyr-dev`](https://gitlab.freedesktop.org/panfrost/linux/-/tree/tyr-dev) branch.
-Make submissions against the downstream Tyr driver by opening a merge request
-against `tyr-dev`. It's expected that `tyr-dev` will be significantly
-refactored before upstreaming.
-
-This split is unfortunately necessary as we do not have the required
-infrastructure in upstream yet, although our plan is to eventually migrate to
-an upstream-only development model once this changes.
-
-We go into more details about why we chose to develop Tyr this way on our
-series of [blog
-posts](https://www.collabora.com/news-and-blog/news-and-events/introducing-tyr-a-new-rust-drm-driver.html)
-at [Collabora's blog](https://www.collabora.com/news-and-blog/). Anyone willing
-to get acquainted with Mali's open source stack should refer to that, as we
-will be covering the whole infrastructure from a simple Vulkan application to
-the actual GPU hardware in Mali's CSF architecture. We will also cover the
-various components needed to write a driver, as well as the status of the
-abstractions needed to interact with them from Rust code.
-
-As it currently stands, our downstream branch can be used to test the
-abstractions that are still being developed. It makes sure that we can write a
-functional driver with the abstractions that are currently being proposed.
 
-## What is the current status of the driver?
 
-The current upstream driver can power up the GPU and probe the device on an
-RK3588 system-on-chip. This lets us read a few sections of ROM in the GPU,
-which in turn lets us provide this information to userspace by means of a
-`DRM_IOCTL_PANTHOR_DEV_QUERY` call.
+## What is the current status of the driver?
 
-This is all that can be done for now in upstream code, at least until the Micro
-Controller Unit can be made to work.
+The current upstream driver can probe and register an Arm Mali Valhall CSF GPU,
+currently tested on RK3588 systems. During probe it enables the required clocks
+and regulators, maps the GPU registers, issues a soft reset, powers on the L2
+block, reads the GPU identification and feature registers, and exposes that
+information to userspace through `DRM_IOCTL_PANTHOR_DEV_QUERY`.
 
-Our downstream branch (`tyr-dev`) provides a full, working prototype that can run GNOME, Weston, and full-screen 3D games like SuperTuxKart: see [Racing karts on a Rust GPU kernel driver](https://www.collabora.com/news-and-blog/news-and-events/racing-karts-on-a-rust-gpu-kernel-driver.html).
+The next major milestone is the Microcontroller Unit (MCU) firmware bring-up.
+Until that is in place, the upstream driver is limited to device probing and
+basic GPU information queries.
 
 ## Can I try it out?
 
-Anyone with a RK3588 SoC can test Tyr, but the driver is not capable of
+Anyone with an RK3588 SoC can test Tyr, but the driver is not capable of
 replacing Panthor yet. A good candidate device is Radxa's
 [ROCK 5B](https://radxa.com/products/rock5/5b/) Single Board Computer.
 
-A good starting point is to use the Tyr driver to run the Panthor [IGT
+A good starting point is to experiment with the Panthor [IGT
 tests](https://gitlab.freedesktop.org/drm/igt-gpu-tools/-/tree/master/tests/panthor).
-While only a subset of the tests pass on the upstream code for the reasons
-highlighted above, they should all pass if run on `tyr-dev`.
-
-Note that Mali GPUs are found in a vast array of devices, and that we will
-support more hardware as we progress in the implementation.
-
-## Contributing
-
-Tyr is open-source software, and as such, anyone interested in its development
-can check our [issue
-board](https://gitlab.freedesktop.org/panfrost/linux/-/issues/?label_name%5B%5D=tyr).
-We will be posting good starting tasks at a future point.
-
-To work on any given task, assign it to yourself and follow up with a merge
-request against `tyr-for-upstream` (for patches targeting the upstream driver)
-or `tyr-dev` (for work in the downstream staging branch).
 
-Please also write the IGT tests needed to ensure that your code works.
+If you would like to contribute, check our [issue
+board](https://gitlab.freedesktop.org/panfrost/linux/-/issues/?label_name%5B%5D=tyr)
+to look for open tasks.
 
 Happy hacking!