A New Patch For Radeon DRM Power Savings

[Pfanne]

one step closer to a fully opensource notebook
great job!

edit:
why did this thread end up in the intel open source section?

[madman2k]

Great. That just leaves Zaphod mode, which wasn't working the last time I checked. Then I can finally switch!

actually this patch is just a first attempt at dynamic power management. It may still take some time until there is something usable in trunk...

[legume]

Great. That just leaves Zaphod mode, which wasn't working the last time I checked. Then I can finally switch!

Of course according to the officially snactioned recent sequel to hhg Zaphod doesn't have two heads anymore - left brain lives in a jar :-)

[FunkyRider]

This is very interesting and useful function, especially for the hi-end big ass GPUs. For my 2900XT, you don't only feel the speed, you can 'Hear' it. If the fan does not revs up all the time using this Power Management code, that's a fantastic thing. I will be more than willing to test it on my 2900XT since it is the worst 'Heater' on the R6/7/8 family so far. However before GPU voltage can be dynamically changed I wouldn't think it can help R600 to cool down much.

Keep up the good work!

[Zajec]

actually this patch is just a first attempt at dynamic power management. It may still take some time until there is something usable in trunk...

However before GPU voltage can be dynamically changed I wouldn't think it can help R600 to cool down much.

In case of my HD 34x0 engine downclocking gave quite nice result already. I did not see much difference when downclocking memory. Not sure what voltage changing will bring. Maybe not much difference to temperature, but some to battery life time?

I really hope to get engine downclocking commited for 2.6.33-rc1. Hopefully Alex will release IRQs before that, so I will able to enable memory downclocking as well for 33-rc1.

[barkas]

In case of my HD 34x0 engine downclocking gave quite nice result already. I did not see much difference when downclocking memory. Not sure what voltage changing will bring. Maybe not much difference to temperature, but some to battery life time?

I really hope to get engine downclocking commited for 2.6.33-rc1. Hopefully Alex will release IRQs before that, so I will able to enable memory downclocking as well for 33-rc1.

heat ~ clock * voltage^2

So voltage should bring more benefit than clock adjustment.

[bridgman]

Not sure about the formula (power tends to follow frequency squared as well) but voltage definitely makes a difference. Memory clock usually needs to be dropped before you can reduce the voltage, and the code to drop memory clocks is tricky because it needs to be sync'ed with display refresh to avoid glitching the display.

[Zajec]

the code to drop memory clocks is tricky because it needs to be sync'ed with display refresh to avoid glitching the display.

Nothing that sounds hard to implement if you just let Alex release the code

[bridgman]

Yep. Some of the review folks were away this week but back Monday; hopefully we can get the IRQ IP released before all the US folks take off for thanksgiving.

[monraaf]

Nothing that sounds hard to implement if you just let Alex release the code

I hope you can pull it off, what I've read is that AMD had some problems with downclocking GDDR5 memory in the past:

Even though ATI has implemented a 2D/3D clock switching model, the power consumption in idle is still quite high. One reason for that is that only the core frequency is reduced, while memory keeps running at full speed for the whole time. During testing I noticed that any memory frequency change will make the screen display flicker, which is probably the reason why AMD chose not to allow dynamic memory clock changes. I am surprised that AMD has not fixed this problem in their second GDDR5-capable GPU.

http://www.techpowerup.com/reviews/ATI/HD_4770/26.html