On 2/16/2024 10:13, Harry Wentland wrote:
On 2024-02-16 11:11, Harry Wentland wrote:
On 2024-02-16 10:42, Pekka Paalanen wrote:
On Fri, 16 Feb 2024 09:33:47 -0500
Harry Wentland <harry.wentland@xxxxxxx> wrote:
On 2024-02-16 03:19, Pekka Paalanen wrote:
On Fri, 2 Feb 2024 10:28:35 -0500
Hamza Mahfooz <hamza.mahfooz@xxxxxxx> wrote:
We want programs besides the compositor to be able to enable or disable
panel power saving features.
Could you also explain why, in the commit message, please?
It is unexpected for arbitrary programs to be able to override the KMS
client, and certainly new ways to do so should not be added without an
excellent justification.
Maybe debugfs would be more appropriate if the purpose is only testing
rather than production environments?
However, since they are currently only
configurable through DRM properties, that isn't possible. So, to remedy
that issue introduce a new "panel_power_savings" sysfs attribute.
When the DRM property was added, what was used as the userspace to
prove its workings?
I don't think there ever was a userspace implementation and doubt any
exists today. Part of that is on me. In hindsight, the KMS prop should
have never gone upstream.
I suggest we drop the KMS prop entirely.
Sounds good. What about the sysfs thing? Should it be a debugfs thing
instead, assuming the below question will be resolved?
It's intended to be used by the power profiles daemon (PPD). I don't think
debugfs is the right choice. See
https://gitlab.freedesktop.org/upower/power-profiles-daemon/-/commit/41ed5d33a82b0ceb7b6d473551eb2aa62cade6bc
As for the color accuracy topic, I think it is important that compositors
can have full control over that if needed, while it's also important
for HW vendors to optimize for power when absolute color accuracy is not
needed. An average end-user writing code or working on their slides
would rather have a longer battery life than a perfectly color-accurate
display. We should probably think of a solution that can support both
use-cases.
I agree. Maybe this pondering should start from "how would it work from
end user perspective"?
"Automatically" is probably be most desirable answer. Some kind of
I agree
desktop settings with options like "save power at the expense of image
quality":
- always
- not if watching movies/gaming
- on battery
- on battery, unless I'm watching movies/gaming
- never
It's interesting that you split out movies/gaming, specifically. AMD's
ABM algorithm seems to have considered movies in particular when
evaluating the power/fidelity trade-off.
I wouldn't think consumer media is very particular about a specific
color fidelity (despite what HDR specs try to make you believe). Where
color fidelity would matter to me is when I'd want to edit pictures or
video.
The "abm_level" property that we expose is really just that, a setting
for the strength of the power-savings effect, with 0 being off and 4 being
maximum strength and power saving, at the expense of fidelity.
Mario's work is to let the PPD control it and set the ABM levels based on
the selected power profile:
0 - Performance
1 - Balance
3 - Power
And I believe we've looked at disabling ABM (setting it to 0) automatically
if we know we're on AC power.
Or maybe there already is something like that, and it only needs to be
plumbed through?
Which would point towards KMS clients needing to control it, which
means a generic KMS prop rather than vendor specific?
Or should the desktop compositor be talking to some daemon instead of
KMS for this? Maybe they already are?
I think the intention is for the PPD to be that daemon. Mario can elaborate.
Some more details and screenshots on how the PPD is expected to work and look:
https://linuxconfig.org/how-to-manage-power-profiles-over-d-bus-with-power-profiles-daemon-on-linux
Right, thanks!
The most important point is that the user indicates intent from the GUI.
The daemon orchestrates the various knobs to get that intent.
It's intentionally very coarse - 3 power states. The policy of what to
do for those states is managed by the daemon.
In the case of ABM it will only apply the policy if the daemon detects
the system is on battery.
