Re: [PATCH v4] accel/rocket: Report NPU usage through fdinfo

[Gyeyoung Baek]

Hi Sidong,

On Wed, Nov 4, 2026 at 12:53 AM Sidong Yang <sidong.yang@xxxxxxxxxx> wrote:
>
> There is no way to tell how much of the NPU a client uses. Implement the
> DRM usage stats: account the time each job occupies a core and report
> it per client as drm-engine-npu, along with drm_show_memory_stats() for
> the BOs.
>
> The cores are identical, so they are reported as a single engine with
> drm-engine-capacity-npu set to rdev->max_cores, the number of core
> slots. The time is summed over all cores, with an atomic counter as the
> cores complete jobs concurrently.
>
> Jobs can outlive the file that submitted them, so the counter is
> refcounted and each job holds a reference. The time covers the whole
> period a job owns a core, so it also includes handling the completion
> interrupt and the gaps between the tasks of a multi-task job.

nit: "the time completed jobs occupy a core" would be more accurate than
"the whole period", as timed-out jobs are not accounted.


>  * RK3588
> +
> +.. _rocket-usage-stats:
> +
> +Rocket DRM client usage stats implementation
> +============================================
> +
> +The accel/rocket driver implements the DRM client usage stats specification as
> +documented in :ref:`drm-client-usage-stats`.
> +
> +The NPU cores are reported as a single engine, npu, with a capacity equal to the
> +number of cores. The time is summed over all cores, and covers the whole period
> +a job occupies a core.

Same here

> @@ -139,7 +183,28 @@ static const struct drm_ioctl_desc rocket_drm_driver_ioctls[] = {
>         ROCKET_IOCTL(FINI_BO, fini_bo),
>  };
>
> -DEFINE_DRM_ACCEL_FOPS(rocket_accel_driver_fops);
> +static void rocket_show_fdinfo(struct drm_printer *p, struct drm_file *file)
> +{
> +       struct rocket_device *rdev = to_rocket_device(file->minor->dev);
> +       struct rocket_file_priv *rocket_priv = file->driver_priv;
> +
> +       /*
> +        * This is an estimate: the time is taken around the whole period a job
> +        * occupies a core, so it also covers handling the completion interrupt
> +        * and, for a job made of several tasks, the gaps between them.
> +        */

And here.

with these addressed:

Tested on RK3588: no OOB access, and fdinfo reads correctly with several
apps running concurrently.

Reviewed-by: Gyeyoung Baek <gyeyoung7182@xxxxxxxxx>
Tested-by: Gyeyoung Baek <gyeyoung7182@xxxxxxxxx>

-- 
Thanks,
Gyeyoung