gru: should we use ddrfreq as a passive cooling device? |
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Issue descriptionIn veyron, we used DDRFreq as a passive cooling device. It was found that lowering the CPU speed without also lowering the DDRFreq ended up just wasting power. It was much more effective to lower both together. It seems like we should do the same on gru based devices, like bob and kevin. On gru-based devices, this should actually be much easier than it was on veyron. On veyron we got into trouble when we tried to scale DDRFreq when the CPU was too slow. Presumably the more advanced DDRFreq architecture on gru should mean we don't need to worry so much. --- I'd be kinda curious if they helps on any of our benchmarks. Do PageCycler and/or powerLoadTest end up thermally constrained? If so, this might be a nice help.
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May 27 2017
Indeed, I have a look at the thermal of Bob in recently. And run the scripts to check, the dmc always run 928M when we turn on the targer temperature. /sys/class/thermal/thermal_zone[0-1]/temp /sys/devices/sy stem/cpu/cpu[0-5]/cpufreq/scaling_cur_freq /sys/devices/platform/ff9a0000.gpu/devfreq/ff9a0000.gpu/cur_freq /sys/class/devfreq/dmc/cur_freq; date; sleep .5; done
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May 30 2017
@wxt: do you want to try adding some patches for this? I don't remember it being very difficult to make it a cooling device. Trying to figure out how to integrate it with IPA might be harder, though.
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May 31 2017
Okay, I try to do this week and will update something here.
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Jun 1 2017
Copy from the Doug's solution on mickey of rk3288. Posted CL as following.
https://chromium-review.googlesource.com/521003 WIP: CHROMIUM: dmcfreq: Allow the DMC to be used as a passive cooling device
https://chromium-review.googlesource.com/521004 WIP: arm64: dts: rockchip: add the dmc thermal for rk3399
It seem works, but no well now.
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Aug 18 2017
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Comment 1 by derat@chromium.org
, May 26 2017