No subject
Tue Nov 29 15:17:46 PST 2011
0.1 and 0.4W when compared to what we had with i915_enable_rc6=1.
But in any case, this is all highly experimental and I'll do more testing
with it :).
--
Eugeni Dodonov
<http://eugeni.dodonov.net/>
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<div class=3D"gmail_quote">On Tue, Nov 29, 2011 at 19:42, Ben Widawsky <spa=
n dir=3D"ltr"><<a href=3D"mailto:ben at bwidawsk.net">ben at bwidawsk.net</a>&=
gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 =
0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class=3D"im">On Tue, Nov 29, 2011 at 01:01:31PM +0000, Chris Wilson wr=
ote:<br>
> On Tue, 29 Nov 2011 10:55:04 -0200, Eugeni Dodonov <<a href=3D"mail=
to:eugeni.dodonov at intel.com">eugeni.dodonov at intel.com</a>> wrote:<br>
> > This should allow even more energy saving when GPU is not in use.=
<br>
> > According to the testing, this state results in around 0.1 - 0.4 =
W better<br>
> > power usage.<br>
> ><br>
> > No issues or regressions observed so far, but additional testing =
is<br>
> > certainly welcome.<br>
><br>
> The docs I saw said "not implemented; do not use". Do we hav=
e it on good<br>
> authority that this is safe and useful to enable? And doesn't it<b=
r>
> require programming of more transition thresholds?<br>
> -Chris<br>
<br>
</div>Yes, I think we do have to program more stuff to make this work. Perh=
aps<br>
the BIOS puts in decent values for these registers though? We would have<br=
>
to restore those on reset and resume I'd guess. If BIOS doesn't use=
<br>
anything there, you probably aren't even entering these states.<br>
<br>
Also, for posterity, there are 3 rc6 states, rc6, deep rc6, and deepest<br>
rc6. I think deepest rc6 was recommended to avoid (though I don't recal=
l<br>
a specific root caused issue, just some data from Jesse, from the<br>
windows team that it didn't seem stable). And I think deepest rc6 is<br=
>
also referred to as rc7 sometimes.<br></blockquote><div><br>We already setu=
p the variables for both deep and deepest rc6 in our driver (GEN6_RC6p_* an=
d GEN6_RC6pp_*), but we weren't using this additional state previously =
- if I understood the documentation and the code correctly, we do enable pl=
ain rc6
and deep rc6 currently. I haven't found any indications which would te=
ll to avoid it in the latest docs, and I also haven't seen any regressi=
ons or issues with it being enabled on any of the machines, so I thought it=
would be worth trying that=20
additional state as well.<br><br>From the testing which QA did for this pat=
ch, looks like we save between 0.1 and 0.4W when compared to what we had wi=
th i915_enable_rc6=3D1.<br></div></div><br>But in any case, this is all hig=
hly experimental and I'll do more testing with it :).<br clear=3D"all">
<br>-- <br>Eugeni Dodonov<a href=3D"http://eugeni.dodonov.net/" target=3D"_=
blank"><br></a><br>
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