Hi Doug,

On 10/2/20 4:47 PM, Doug Anderson wrote:

Hi,

On Fri, Oct 2, 2020 at 8:13 AM Lukasz Luba [off-list ref] wrote:

quoted

Hi Doug,

On 10/2/20 3:31 PM, Doug Anderson wrote:

quoted

Hi,

On Fri, Oct 2, 2020 at 4:45 AM Lukasz Luba [off-list ref] wrote:

quoted

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.

I guess the problem is that Rajendra is currently planning to remove
all the "dynamic-power-coefficient" values from device tree right now
and move them to the source code because the numbers we currently have
in the device tree _are_ in abstract scale and thus violate the
bindings.  Moving this to source code won't help us get to more real
power numbers (since it'll still be abstract scale), it'll just be
pure churn.  If we're OK with the abstract scale in general then we
should allow it everywhere and not add churn for no reason.

I just want to notify you that I had internal conversation about this
'dynamic-power-coefficient' binding and abstract scale. We would
change it as well, similarly to 'sustainable-power'. It must pass
internal review and I will send the v3 of this series.

Regards,
Lukasz