We have the following problem: our processor produces a lot of heat and our hardware engineer thinks that clocking down might help,
is there any way to clock the processor down?
Clocking down
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- Add in kernel drivers/clk/imx/clk-imx8mm.c (line 41)
- static const struct imx_pll14xx_rate_table imx8mm_pll1416x_tbl[] = {
- PLL_1416X_RATE(1800000000U, 225, 3, 0),
- PLL_1416X_RATE(1600000000U, 200, 3, 0),
- PLL_1416X_RATE(1200000000U, 300, 3, 1),
- PLL_1416X_RATE(1000000000U, 250, 3, 1),
- PLL_1416X_RATE(800000000U, 200, 3, 1),
- PLL_1416X_RATE(750000000U, 250, 2, 2),
- PLL_1416X_RATE(700000000U, 350, 3, 2),
- PLL_1416X_RATE(600000000U, 300, 3, 2),
- PLL_1416X_RATE(400000000U, 200, 3, 2), <- Add new entry for 400MHz
- };
- Add in arch/arm64/boot/dts/freescale/imx8mm.dtsi (line 130) following code block
- opp-400000000 {
- opp-hz = /bits/ 64 <400000000>;
- opp-supported-hw = <0xe>, <0x7>;
- opp-microvolt = <850000>;
- clock-latency-ns = <150000>;
- opp-suspend;
- };
- opp-800000000 {
- opp-hz = /bits/ 64 <800000000>;
- clock-latency-ns = <150000>;
- opp-microvolt = <850000>;
- opp-supported-hw = <0xe>, <0x7>;
- opp-suspend;
- };
- Export 800MHz and 400MHz values in sysfs by adding two extra nodes in device tree.
- But unfortunately regarding heat that will not help much. Anyway good luck.
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well what would help? except a bigger cooling surface / active cooling.
is it possible to disable the gpu/vpu on the fly, or is cpu standby an option.
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We are also looking into CPU temperature. Currently with low load, the core is reporting around 55degs, in ambient of around 25degs.
We only have a heatspreader (not a heatsink). NXP AN13054 leads me to expect more like 40degs.
So far I have tried disabling 3 of the 4 A53 cores (in uboot, set "extra" to "maxcpus=1"), and also using the LCD enabled device tree vs no LCD. Neither had a significant impact on temperature.
It would be great if others would share their cooling setup and temperatures etc. -
Everything will help a little (down-scaling, disabling cores) but at the end not enough for putting a module in closed box. Active cooling is required by my opinion. I am not sure how you connect module on base board but if you use standard connectors from development kit big part of module is floating in air. Soldering complete module is much better option for thermal exchange between module and baseboard or putting filament to close the gap.
Since this thread is active I will ask some other question since I got no support. Did any of you try using mPCIE port for real mPCIE transfers not USB.
