[PATCH 6/6] Documentation/gpu: Add an intro about MES

[Bagas Sanjaya]

On Tue, Mar 25, 2025 at 11:18:47AM -0600, Rodrigo Siqueira wrote:
> diff --git a/Documentation/gpu/amdgpu/gc/mes.rst b/Documentation/gpu/amdgpu/gc/mes.rst
> new file mode 100644
> index 000000000000..b99eb211b179
> --- /dev/null
> +++ b/Documentation/gpu/amdgpu/gc/mes.rst
> @@ -0,0 +1,38 @@
> +.. _amdgpu-mes:
> +
> +=============================
> + MicroEngine Scheduler (MES)
> +=============================
> +
> +.. note::
> +   Queue and ring buffer are used as a synonymous.
> +
> +.. note::
> +   This section assumes that you are familiar with the concept of Pipes, Queues, and GC.
> +   If not, check :ref:`GFX, Compute, and SDMA Overall Behavior<pipes-and-queues-description>`
> +   and :ref:`drm/amdgpu - Graphics and Compute (GC) <amdgpu-gc>`.
> +
> +Every GFX has a pipe component with one or more hardware queues. Pipes can
> +switch between queues depending on certain conditions, and one of the
> +components that can request a queue switch to a pipe is the MicroEngine
> +Scheduler (MES). Whenever the driver is initialized, it creates one MQD per
> +hardware queue, and then the MQDs are handed to the MES firmware for mapping
> +to:
> +
> +1. Kernel Queues (legacy): This queue is statically mapped to HQDs and never
> +   preempted. Even though this is a legacy feature, it is the current default, and
> +   most existing hardware supports it. When an application submits work to the
> +   kernel driver, it submits all of the application command buffers to the kernel
> +   queues. The CS IOCTL takes the command buffer from the applications and
> +   schedules them on the kernel queue.
> +
> +2. User Queues: These queues are dynamically mapped to the HQDs. Regarding the
> +   utilization of User Queues, the userspace application will create its user
> +   queues and submit work directly to its user queues with no need to IOCTL for
> +   each submission and no need to share a single kernel queue.
> +
> +In terms of User Queues, MES can dynamically map them to the HQD. If there are
> +more MQDs than HQDs, the MES firmware will preempt other user queues to make
> +sure each queues get a time slice; in other words, MES is a microcontroller
> +that handles the mapping and unmapping of MQDs into HQDs, as well as the
> +priorities and oversubscription of MQDs.

The doc LGTM, thanks!

Reviewed-by: Bagas Sanjaya <bagasdotme at gmail.com>

-- 
An old man doll... just what I always wanted! - Clara
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