linux-kernel - Re: [PATCH] drm/lima: add governor data with pre-defined thresholds

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Date:   Wed, 27 Jan 2021 10:24:48 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Christian Hewitt <christianshewitt@...il.com>
Cc:     Qiang Yu <yuq825@...il.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, lima@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Steven Price <steven.price@....com>
Subject: Re: [PATCH] drm/lima: add governor data with pre-defined thresholds

Hi Christian,

On 1/25/21 8:18 AM, Christian Hewitt wrote:
> This patch adapts the panfrost pre-defined thresholds change [0] to the
> lima driver to improve real-world performance. The upthreshold value has
> been set to ramp GPU frequency to max freq faster (compared to panfrost)
> to compensate for the lower overall performance of utgard devices.
> 
> [0] https://patchwork.kernel.org/project/dri-devel/patch/20210121170445.19761-1-lukasz.luba@arm.com/
> 
> Signed-off-by: Christian Hewitt <christianshewitt@...il.com>
> ---
> I have been using Kodi as my test application. If you scroll in library
> views with hundreds of list items and the panfrost values the slow GPU
> ramp up is quite noticeable and the GUI feels sluggish. As everything
> lima runs on is inherently slower than panfrost using devices I believe
> it's better to ramp up to max freq quicker.

It's quite low value for the upthreshold, but I believe you have
experimented and observed that a bit higher (30, 40?) don't work well.
I don't know the Kodi system, though.

You can check if the other frequencies are also used in statistics for
devfreq device:
cat /sys/class/devfreq/<your_gpu>/trans_stats

If they are also used, then it OK (better than stuck at min freq).

Regards,
Lukasz