AMD/ATI PowerPlay-Support in radeon(ati) or radeonHD?

Vedran Rodic vrodic at
Thu Apr 3 09:11:01 PDT 2008

>  We have plans to support it in the free drivers, we just haven't
>  gotten around to it yet.   There are several aspects to powerplay,
>  some are driver controlled others are hw controlled.  Some of the hw
>  controls can already be implemented based on the documentation we've
>  released, it's just that no one has done it yet.  The rest will come
>  eventually.

But the documentation is lacking: We only have a list of registers
without really knowing which ones we can touch, and we also don't know
any details of how they work together, on what versions of hardware

I have a rv670, and I just assumed that the rv620 documentation
applies for it too. I wanted to be able to control the clock (to
downclock the GPU since I've noticed that Windows does that and that
my GPU cooler is a lot less warmer in Windows). But it's really hard
to understand clock and power management registers just by a brief
list and a really insufficient explanations on the rightmost column.

I've tried setting the GLOBAL_PWRMGT_EN bit in GENERAL_PWRMGT register
(while turning off STATIC_PM_EN bit because it seemed logical), and I
got flying animated garbage as a result.

On the other hand, I've enabled DYNAMIC_GFX_ISLAND_POWER_DOWN and
DYNAMIC_GFX_ISLAND_LP in SCLK_PWRMGT_CNTL without any readily visible
side effects.

To monitor the temperature,  my only choice is to reboot to Windows
and measure there (since I don't have an infrared thermometer) hoping
that I will still see the temperature difference in time.

I don't know what temperature sensor chip the card has, how is it
connected on the card, and even if I knew, I'd probably had to write a
I2C bus driver for the card before I start monitoring the temperature.
And I2C is also complex. There is around 33 I2C registers (okay I
guess I can ignore the DDC ones), but still it's hard to write a i2c
driver without some more detailed explanation of the registers.

It's really not hard to admire the people that have the will to write
the drivers using this documentation only, so kudos to you guys,
you're our heroes!


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