[Bug 111482] Sapphire Pulse RX 5700 XT power consumption

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111482

--- Comment #17 from Robert <freedesktop at postfach.xyz> ---
Thanks Andrew! I played around a little bit with the refresh rates. Between
40-60Hz there is no difference in idle power consumption. The mem clock stays
at 875Mhz and can't be changed.

The best refresh rate with 8W idle power consumption I could get was at 39Hz:

cvt12 5120 1440 39 -b
xrandr --output DisplayPort-2 --newmode "5120x1440_39.00_rb2" 297.51  5120 5128
5160 5200  1440 1453 1461 1467 +hsync -vsync
xrandr --output DisplayPort-2 --addmode DisplayPort-2 "5120x1440_39.00_rb2"
xrandr --output DisplayPort-2 --mode "5120x1440_39.00_rb2"

This causes the mem clock to go up to 625Mhz at first but it can be switched
back to 100Mhz with

echo "0" > /sys/class/drm/card0/device/pp_dpm_mclk

Regarding my statement when using 30Hz in the last comment:

"""
It basically works but moving windows a little bit faster or moving the mouse
pointer around looks "interesting".
"""

For this "flickering" that I saw and which was quite annoying I found a
workaround :-) It looked like something didn't refresh fast enough. So I
thought playing around with some frequencies would be a good idea... And the
mem clock was the obvious one to start with. So I was setting the mem clock to
500Mhz with

echo "1" > /sys/class/drm/card0/device/pp_dpm_mclk

Then the "flickering" went away :-) But of course that brought idle power
consumption to 24W. So just for fun I switched back to 100Mhz with

echo "0" > /sys/class/drm/card0/device/pp_dpm_mclk

Funny enough the "flickering" stayed away :-))) So for now after I start KDE
plasma I enter Konsole and execute

echo "1" > /sys/class/drm/card0/device/pp_dpm_mclk
echo "0" > /sys/class/drm/card0/device/pp_dpm_mclk

and be happy :D

One final observation: I tried out kernel 5.3-rc8. With that kernel there is no
way to reduce idle power consumption. It stays at 34W regardless what you do.
But with this tag
https://cgit.freedesktop.org/~agd5f/linux/tag/?h=drm-next-5.4-2019-08-30 (which
basically is kernel 5.3-rc3 with the Navi10 patches for kernel 5.4 - if I got
it right ;-) ) idle power consumption is as expected. 

So my whole issue basically comes down to this: If you have a resolution of
5120x1440 and a refresh rate of > 39Hz your idle power consumption stays at max
and there is (at least until now) nothing you can do about it. So if I had used
a lower resolution or a smaller screen I wouldn't have had an issue at all ;-)
S... happens :D

But anyways: Thanks so much for your help and also to Ilia! I'm now happy with
my setup so far. It would be very interesting if there is really some kind of a
cap with 5120x1444 at 39Hz or if this this "only" a firmware problem, a driver
problem, a config error or something completely different. Maybe we'll find out
in our next lives :D

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