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** Changed in: linux (Ubuntu)
Status: New => Incomplete
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https://bugs.launchpad.net/bugs/1869924
Title:
High power consumption by Intel iGPU on Skylake+
Status in linux package in Ubuntu:
Incomplete
Status in linux source package in Focal:
Incomplete
Bug description:
There is an outstanding regression in i915 that breaks the RC6 power
state for Intel iGPUs on Skylake and newer. This bug was fixed
upstream in Linux 5.5. I submitted a backport of the fix for 5.4
upstream [1].
My cover letter [2] describes the issue:
The first bug, fixed by "drm/i915/gt: Schedule request retirement when
timeline idles" upstream, is very high power consumption by i915 hardware due
to an old commit that broke the RC6 power state for the iGPU on Skylake+. On my
laptop, a Dell Precision 5540 with an i9-9880H, the idle power consumption of
my laptop with this commit goes down from 10 W to 2 W, saving a massive 8 W of
power. On other Skylake+ laptops I tested, this commit reduced idle power
consumption by at least a few watts. The difference in power consumption can be
observed by running `powertop` while disconnected from the charger, or by using
the intel-undervolt tool [1] and running `intel-undervolt measure` which
doesn't require being disconnected from the charger. The psys measurement from
intel-undervolt is the one of interest.
Backporting this commit was not trivial due to i915's high rate of
churn, but the backport didn't require changing any code from the
original commit; it only required moving code around and not altering
some #includes.
[1]
https://lore.kernel.org/stable/20200330033057.2629052-3-sul...@kerneltoast.com/
[2]
https://lore.kernel.org/stable/20200330033057.2629052-1-sul...@kerneltoast.com/
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