Re: DVFS in Intel graphic chips

[Daniel Vetter <daniel.vetter@xxxxxxxx>]

Adding relevant mailing lists, please don't send me i915 related mails in private.

On Tue, Sep 2, 2014 at 11:52 PM, Hadi <am.hadi@xxxxxxxxx> wrote:

Dear Daniel,

I am PhD student in UW-Madison. I have a question about Intel i915 and I was wondering if you could possibly answer it. I have worked with Intel CPU DVFS (dynamic voltage and frequency scaling), and also cpuidle driver (for changing c-states). I was wondering if the same thing could be done on Intel graphic chips (changing frequency and sleep states for gpu). As far as I understood from the datasheet, turning off different parts of Intel gpu can only be done internally (sleep states), so is there any way to change the frequency?

 

At least on all recent intel gpus supported by the i915 driver it's possible and we do it. In sysfs there's files to set the min/max frequencies the driver is allowed to select. By default we scale (depending upon the load) over the full frequency range the gpu supports.

If you want to read up on the driver code for this grep for "rps" - that should dig up all the relevant stuff.

Unfortunately this isn't documented in the public prm.

Cheers, Daniel

Thank you

Hadi Asgharimoghaddam

Research Assistant at UW-Madison 

--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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