Messages in this thread | | | From | Tyler Hall <> | Date | Wed, 25 Feb 2015 14:47:11 -0500 | Subject | Re: [PATCH] thermal: armada: read stable temp on Armada XP |
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Hi Gregory, Eduardo,
On Wed, Feb 25, 2015 at 05:10:14PM +0100, Gregory CLEMENT wrote: > By using it by default do you mean removing marvell,armadaxp-thermal > and adding armadaxp-filtered-thermal instead ?
Yes, replacing it in device tree. For me, /sys/class/thermal/thermal_zone0/temp returns the same temperature but with less variability between samples. My intent was to switch the source of the data and not affect user space other than providing a more stable reading.
> Tyler, > In the meantime could you double check your values? The temperature on my board > seemed broken on my board. If needed I can check on an other board. By the way > on which board/product did you try it?
I'm on a custom board with the 4-core MV78460. In addition to my patch, this is new device tree entry.
thermal@184c4 { compatible = "marvell,armadaxp-filtered-thermal"; reg = <0x184c4 0x4 0x184d0 0x4>; status = "okay"; };
I dumped some raw samples of the temperature fields in each of these registers. This CSV contains the raw values converted to decimal. http://pastebin.com/Umc3cy5L The first column is the current register at 0x182b0 27:19 and the second is the register at 0x184c4 9:1.
Here's a quick plot of a larger sample size while the temperature was rising. https://imgur.com/E9HlSBx The blue value is the current 0x182b0 register which seems to bounce around the green value from 0x184c4.
I'll try a test of instantiating both at the same time and comparing the final output of the driver.
On Wed, Feb 25, 2015 at 1:39 PM, Eduardo Valentin <edubezval@gmail.com> wrote: >> Does that new thermal sensors only improve the stability or does it >> also modify the value? >> >> In the second case it will more or less break the user space expectation. > > Yeah, I agree here. We need to understand if this is: > (1) a fix of which register to use. In that case, the old dtbs are > essentially wrong, and the driver would need to adapt, I would say. > (2) a way to report better temperature extrapolations. then, this is > essentially a new temp sensor, and we should have two separated > compatible. in other words, just keep the patch the way it is.
This *might* be a different physical sensor, or it could be from the same source with some averaging/filtering applied in hardware. The conversion formula is the same, however, and I get similar raw values from both.
> Yes. Typically I ask to see the complete series, even if I am not taking > the DTS changes. That is, you send a complete series, with changes in > the kernel code and in the DTS, copying the required audience (from > kernel side and from DT side). Once the changes are accepted, the > patches will be picked by the correct tree maintainer. It is common that > DTS changes go via the platform tree, to avoid conflicts though.
Thanks for the clarification. I'll send both in the next version as I suspect there will be a v2 of this change.
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