[Bug 91880] Radeonsi on Grenada cards (r9 390) exceptionally unstable and poorly performing

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91880

--- Comment #125 from Christoph Seifert <christoph.seifert27 at googlemail.com> ---
For me switching power states does also result in a system freeze. With
radeon.dpm = 0 everthing is working properly but slowly. If I switch manually
to another power profile (e.g. echo high >
/sys/class/drm/card0/device/power_profile) I got a freeze likewise. With
radeon.dpm = 1 the freeze happens after a few seconds of video playback or some
other load, ergo if the card changes its power profile.

The work around (k firmware) from comment #115 does not work for me. Same
behaviour as without.

So I tried disabling specific DPM features as suggested by Alex Deucher in
comment #60. Disabling mclk (pi->mclk_dpm_key_disabled = 1) does the trick for
my card but the performance is similar to the radeon.dpm = 0 kernel parameter.

With radeon.dpm = 1 and only mclk disabled, the sclk (core clock) adjusts just
fine. High on load, low on no load. The mclk (memory clock) is just fixed at
150 Mhz.

So the freezes seems to be caused by switching memory clock.


Any hints for digging deeper?

My card is a MSI Radeon R9 390 too.
Linux Kernel 4.8.6
Mesa 13.0.0rc2

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