Messages in this thread | | | Subject | Re: [PATCH v2 3/3] dt-bindings: thermal: update sustainable-power with abstract scale | From | Lukasz Luba <> | Date | Fri, 2 Oct 2020 16:12:55 +0100 |
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Hi Doug,
On 10/2/20 3:31 PM, Doug Anderson wrote: > Hi, > > On Fri, Oct 2, 2020 at 4:45 AM Lukasz Luba <lukasz.luba@arm.com> wrote: >> >> Update the documentation for the binding 'sustainable-power' and allow >> to provide values in an abstract scale. It is required when the cooling >> devices use an abstract scale for their power values. >> >> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> >> --- >> .../devicetree/bindings/thermal/thermal-zones.yaml | 13 +++++++++---- >> 1 file changed, 9 insertions(+), 4 deletions(-) >> >> diff --git a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml >> index 3ec9cc87ec50..4d8f2e37d1e6 100644 >> --- a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml >> +++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml >> @@ -99,10 +99,15 @@ patternProperties: >> sustainable-power: >> $ref: /schemas/types.yaml#/definitions/uint32 >> description: >> - An estimate of the sustainable power (in mW) that this thermal zone >> - can dissipate at the desired control temperature. For reference, the >> - sustainable power of a 4-inch phone is typically 2000mW, while on a >> - 10-inch tablet is around 4500mW. >> + An estimate of the sustainable power (in mW or in an abstract scale) >> + that this thermal zone can dissipate at the desired control >> + temperature. For reference, the sustainable power of a 4-inch phone >> + is typically 2000mW, while on a 10-inch tablet is around 4500mW. >> + >> + It is possible to express the sustainable power in an abstract >> + scale. This is the case when the related cooling devices use also >> + abstract scale to express their power usage. The scale must be >> + consistent. > > Two thoughts: > > 1. If we're going to allow "sustainable-power" to be in abstract > scale, why not allow "dynamic-power-coefficient" to be in abstract > scale too? I assume that the whole reason against that originally was > the idea of device tree purity, but if we're allowing the abstract > scale here then there seems no reason not to allow it for > "dynamic-power-coefficient".
With this binding it's a bit more tricky. I also have to discuss a few things internally. This requirement of uW/MHz/V^2 makes the code easier also for potential drivers like GPU (which are going to register the devfreq cooling with EM).
Let me think about it, but for now I would just update these bits. These are required to proper IPA operation, the dyn.-pow.-coef. is a nice to have and possible next step.
> > 2. Is it worth adding some type of indication of what type of units > "sustainable-power" is represented in? Maybe even a made up unit so > that you could tell the difference between made up units in the same > system? I'd envision something like: > > sustainable-power-units = "qualcomm,sc7180-bogoWatts" > > ...and on the dynamic-power-coefficient side, the same: > > dynamic-power-coefficient-units = "qualcomm,sc7180-bogoWatts" > > One could imagine someone even later (after devices are widely > distributed) figuring out translations between these bogoWatts numbers > and real Watts if someone could come up with a case where it matters.
To figure this out we don't need a new binding. I think a simple comment in the DT would be enough for this, even e.g.:
sustainable-power = <100> /* bogoWatts */
Thank you for your comments. BTW, I haven't put your 'Reviewed-by' because I have added this sustainable-power new stuff in patch 1/3. I will grateful if you have a look on that.
Regards, Lukasz
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