Re: [RFC PATCH 0/4] thermal: Introduce support for monitoring falling temperature

[Thara Gopinath]

On 7/15/20 4:27 AM, Zhang Rui wrote:

Hi, Thara,

On Tue, 2020-07-14 at 17:39 -0400, Thara Gopinath wrote:




For example, to support this, we can
either
introduce both "cold" trip points and "warming devices", and
introduce
new logic in thermal framework and governors to handle them,
Or
introduce "cold" trip point and "warming" device, but only
semantically, and treat them just like normal trip points and
cooling
devices. And strictly define cooling state 0 as the state that
generates most heat, and define max cooling state as the state that
generates least heat. Then, say, we have a trip point at -10C, the
"warming" device is set to cooling state 0 when the temperature is
lower than -10C, and in most cases, this thermal zone is always in
a
"overheating" state (temperature higher than -10C), and the
"warming"
device for this thermal zone is "throttled" to generate as least
heat
as possible. And this is pretty much what the current code has
always
been doing, right?



IMHO, thermal framework should move to a direction where the term
"mitigation" is used rather than cooling or warming. In this case
"cooling dev" and "warming dev" should will become
"temp-mitigating-dev". So going by this, I think what you mention as
option 1 is more suitable where new logic is introduced into the
framework and governors to handle the trip points marked as "cold".

Also in the current set of requirements, we have a few power domain
rails and other resources that are used exclusively in the thermal
framework for warming alone as in they are not used ever for cooling
down a zone. But then one of the requirements we have discussed is
for cpufreq and gpu scaling to be behave as warming devices where
the minimum operating point/ voltage of the relevant cpu/gpu is
restricted.
So in this case, Daniel had this suggestion of introducing negative
states for presently what is defined as cooling devices. So cooling
dev
/ temp-mitigation-dev states can range from say -3 to 5 with 0 as
the
good state where no mitigation is happening. This is an interesting
idea
though I have not proto-typed it yet.


Agreed. If some devices support both "cooling" and "warning", we should
have only one "temp-mitigating-dev" instead.




I can not say which one is better for now as I don't have the
background of this requirement. It's nice that Thara sent this RFC
series for discussion, but from upstream point of view, I'd prefer
to
see a full stack solution, before taking any code.


We had done a session at ELC on this requirement. Here is the link
to
the presentation. Hopefully it gives you some back ground on this.


yes, it helps. :)




https://elinux.org/images/f/f7/ELC-2020-Thara-Ram-Linux-Kernel-Thermal-Warming.pdf


I have sent across some patches for introducing a generic power
domain
warming device which is under review by Daniel.

So how do you want to proceed on this? Can you elaborate a bit more
on
what you mean by a full stack solution.


I mean, the patches, and the idea look good to me, just with some minor
comments. But applying this patch series, alone, does not bring us
anything because we don't have a thermal zone driver that supports cold
trip point, right?
I'd like to see this patch series together with the support in
thermal_core/governors and real users like updated/new thermal
zone/cdev drivers that supports the cold trip point and warming
actions.
Or else I've the concern that this piece of code may be changed back
and forth when prototyping the rest of the support.


Got it! I will try to include more pieces in the next version.



thanks,
rui



--
Warm Regards
Thara

Re: [RFC PATCH 0/4] thermal: Introduce support for monitoring falling temperature

[Zhang Rui]

Hi, Thara,

On Tue, 2020-07-14 at 17:39 -0400, Thara Gopinath wrote:
> 
> > 
> > For example, to support this, we can
> > either
> > introduce both "cold" trip points and "warming devices", and
> > introduce
> > new logic in thermal framework and governors to handle them,
> > Or
> > introduce "cold" trip point and "warming" device, but only
> > semantically, and treat them just like normal trip points and
> > cooling
> > devices. And strictly define cooling state 0 as the state that
> > generates most heat, and define max cooling state as the state that
> > generates least heat. Then, say, we have a trip point at -10C, the
> > "warming" device is set to cooling state 0 when the temperature is
> > lower than -10C, and in most cases, this thermal zone is always in
> > a
> > "overheating" state (temperature higher than -10C), and the
> > "warming"
> > device for this thermal zone is "throttled" to generate as least
> > heat
> > as possible. And this is pretty much what the current code has
> > always
> > been doing, right?
> 
> 
> IMHO, thermal framework should move to a direction where the term 
> "mitigation" is used rather than cooling or warming. In this case 
> "cooling dev" and "warming dev" should will become 
> "temp-mitigating-dev". So going by this, I think what you mention as 
> option 1 is more suitable where new logic is introduced into the 
> framework and governors to handle the trip points marked as "cold".
> 
> Also in the current set of requirements, we have a few power domain 
> rails and other resources that are used exclusively in the thermal 
> framework for warming alone as in they are not used ever for cooling 
> down a zone. But then one of the requirements we have discussed is
> for cpufreq and gpu scaling to be behave as warming devices where
> the minimum operating point/ voltage of the relevant cpu/gpu is
> restricted.
> So in this case, Daniel had this suggestion of introducing negative 
> states for presently what is defined as cooling devices. So cooling
> dev 
> / temp-mitigation-dev states can range from say -3 to 5 with 0 as
> the 
> good state where no mitigation is happening. This is an interesting
> idea 
> though I have not proto-typed it yet.

Agreed. If some devices support both "cooling" and "warning", we should
have only one "temp-mitigating-dev" instead.
> 
> > 
> > I can not say which one is better for now as I don't have the
> > background of this requirement. It's nice that Thara sent this RFC
> > series for discussion, but from upstream point of view, I'd prefer
> > to
> > see a full stack solution, before taking any code.
> 
> We had done a session at ELC on this requirement. Here is the link
> to 
> the presentation. Hopefully it gives you some back ground on this.

yes, it helps. :)
> 
> 
https://elinux.org/images/f/f7/ELC-2020-Thara-Ram-Linux-Kernel-Thermal-Warming.pdf
> 
> I have sent across some patches for introducing a generic power
> domain 
> warming device which is under review by Daniel.
> 
> So how do you want to proceed on this? Can you elaborate a bit more
> on 
> what you mean by a full stack solution.

I mean, the patches, and the idea look good to me, just with some minor
comments. But applying this patch series, alone, does not bring us
anything because we don't have a thermal zone driver that supports cold
trip point, right?
I'd like to see this patch series together with the support in
thermal_core/governors and real users like updated/new thermal
zone/cdev drivers that supports the cold trip point and warming
actions.
Or else I've the concern that this piece of code may be changed back
and forth when prototyping the rest of the support.

thanks,
rui

Re: [RFC PATCH 0/4] thermal: Introduce support for monitoring falling temperature

[Thara Gopinath]

On 7/14/20 9:49 AM, Zhang Rui wrote:

On Mon, 2020-07-13 at 17:03 +0200, Daniel Lezcano wrote:

On 10/07/2020 15:51, Thara Gopinath wrote:

Thermal framework today supports monitoring for rising temperatures
and
subsequently initiating cooling action in case of a thermal trip
point
being crossed. There are scenarios where a SoC need some warming
action to
be activated if the temperature falls below a cetain permissible
limit.
Since warming action can be considered mirror opposite of cooling
action,
most of the thermal framework can be re-used to achieve this.

This patch series is yet another attempt to add support for
monitoring
falling temperature in thermal framework. Unlike the first
attempt[1]
(where a new property was added to thermal trip point binding to
indicate
direction of temperature monitoring), this series introduces a new
trip
point type (THERMAL_TRIP_COLD) to indicate a trip point at which
falling
temperature monitoring must be triggered. This patch series uses
Daniel
Lezcano's recently added thermal genetlink interface[2] to notify
userspace
of falling temperature and rising temperature at the cold trip
point. This
will enable a user space engine to trigger the relevant mitigation
for
falling temperature. At present, no support is added to any of the
thermal
governors to monitor and mitigate falling temperature at the cold
trip
point;rather all governors return doing nothing if triggered for a
cold
trip point. As future extension, monitoring of falling temperature
can be
added to the relevant thermal governor.


I agree we need a cold trip point in order to introduce the
functioning
temperature range in the thermal framework.

Rui, what is your opinion ?


I agree with the concept of "cold" trip point.
In this patch set, the cold trip point is defined with only netlink
event support. But there are still quite a lot of things unclear,
especially what we should do in thermal framework?

Hi Rui,

Thanks for the comments.

You are right that cold trip points are dealt with only by netlink 
events in this patch series. Eventually IMHO, governors should handle 
them with a logic opposite to what is being currently done for non-cold 
trip points.




For example, to support this, we can
either
introduce both "cold" trip points and "warming devices", and introduce
new logic in thermal framework and governors to handle them,
Or
introduce "cold" trip point and "warming" device, but only
semantically, and treat them just like normal trip points and cooling
devices. And strictly define cooling state 0 as the state that
generates most heat, and define max cooling state as the state that
generates least heat. Then, say, we have a trip point at -10C, the
"warming" device is set to cooling state 0 when the temperature is
lower than -10C, and in most cases, this thermal zone is always in a
"overheating" state (temperature higher than -10C), and the "warming"
device for this thermal zone is "throttled" to generate as least heat
as possible. And this is pretty much what the current code has always
been doing, right?



IMHO, thermal framework should move to a direction where the term 
"mitigation" is used rather than cooling or warming. In this case 
"cooling dev" and "warming dev" should will become 
"temp-mitigating-dev". So going by this, I think what you mention as 
option 1 is more suitable where new logic is introduced into the 
framework and governors to handle the trip points marked as "cold".


Also in the current set of requirements, we have a few power domain 
rails and other resources that are used exclusively in the thermal 
framework for warming alone as in they are not used ever for cooling 
down a zone. But then one of the requirements we have discussed is for 
cpufreq and gpu scaling to be behave as warming devices where the 
minimum operating point/ voltage of the relevant cpu/gpu is restricted.
So in this case, Daniel had this suggestion of introducing negative 
states for presently what is defined as cooling devices. So cooling dev 
/ temp-mitigation-dev states can range from say -3 to 5 with 0 as the 
good state where no mitigation is happening. This is an interesting idea 
though I have not proto-typed it yet.




I can not say which one is better for now as I don't have the
background of this requirement. It's nice that Thara sent this RFC
series for discussion, but from upstream point of view, I'd prefer to
see a full stack solution, before taking any code.


We had done a session at ELC on this requirement. Here is the link to 
the presentation. Hopefully it gives you some back ground on this.


https://elinux.org/images/f/f7/ELC-2020-Thara-Ram-Linux-Kernel-Thermal-Warming.pdf

I have sent across some patches for introducing a generic power domain 
warming device which is under review by Daniel.


So how do you want to proceed on this? Can you elaborate a bit more on 
what you mean by a full stack solution.




thanks,
Rui



--
Warm Regards
Thara

Re: [RFC PATCH 0/4] thermal: Introduce support for monitoring falling temperature

[Zhang Rui]

On Mon, 2020-07-13 at 17:03 +0200, Daniel Lezcano wrote:
> On 10/07/2020 15:51, Thara Gopinath wrote:
> > Thermal framework today supports monitoring for rising temperatures
> > and
> > subsequently initiating cooling action in case of a thermal trip
> > point
> > being crossed. There are scenarios where a SoC need some warming
> > action to
> > be activated if the temperature falls below a cetain permissible
> > limit.
> > Since warming action can be considered mirror opposite of cooling
> > action,
> > most of the thermal framework can be re-used to achieve this.
> > 
> > This patch series is yet another attempt to add support for
> > monitoring
> > falling temperature in thermal framework. Unlike the first
> > attempt[1]
> > (where a new property was added to thermal trip point binding to
> > indicate
> > direction of temperature monitoring), this series introduces a new
> > trip
> > point type (THERMAL_TRIP_COLD) to indicate a trip point at which
> > falling
> > temperature monitoring must be triggered. This patch series uses
> > Daniel
> > Lezcano's recently added thermal genetlink interface[2] to notify
> > userspace
> > of falling temperature and rising temperature at the cold trip
> > point. This
> > will enable a user space engine to trigger the relevant mitigation
> > for
> > falling temperature. At present, no support is added to any of the
> > thermal
> > governors to monitor and mitigate falling temperature at the cold
> > trip
> > point;rather all governors return doing nothing if triggered for a
> > cold
> > trip point. As future extension, monitoring of falling temperature
> > can be
> > added to the relevant thermal governor. 
> 
> I agree we need a cold trip point in order to introduce the
> functioning
> temperature range in the thermal framework.
> 
> Rui, what is your opinion ?

I agree with the concept of "cold" trip point.
In this patch set, the cold trip point is defined with only netlink
event support. But there are still quite a lot of things unclear,
especially what we should do in thermal framework?

For example, to support this, we can
either
introduce both "cold" trip points and "warming devices", and introduce
new logic in thermal framework and governors to handle them,
Or
introduce "cold" trip point and "warming" device, but only
semantically, and treat them just like normal trip points and cooling
devices. And strictly define cooling state 0 as the state that
generates most heat, and define max cooling state as the state that
generates least heat. Then, say, we have a trip point at -10C, the
"warming" device is set to cooling state 0 when the temperature is
lower than -10C, and in most cases, this thermal zone is always in a
"overheating" state (temperature higher than -10C), and the "warming"
device for this thermal zone is "throttled" to generate as least heat
as possible. And this is pretty much what the current code has always
been doing, right?

I can not say which one is better for now as I don't have the
background of this requirement. It's nice that Thara sent this RFC
series for discussion, but from upstream point of view, I'd prefer to
see a full stack solution, before taking any code.

thanks,
Rui

Re: [RFC PATCH 0/4] thermal: Introduce support for monitoring falling temperature

[Daniel Lezcano]

On 10/07/2020 15:51, Thara Gopinath wrote:
> Thermal framework today supports monitoring for rising temperatures and
> subsequently initiating cooling action in case of a thermal trip point
> being crossed. There are scenarios where a SoC need some warming action to
> be activated if the temperature falls below a cetain permissible limit.
> Since warming action can be considered mirror opposite of cooling action,
> most of the thermal framework can be re-used to achieve this.
> 
> This patch series is yet another attempt to add support for monitoring
> falling temperature in thermal framework. Unlike the first attempt[1]
> (where a new property was added to thermal trip point binding to indicate
> direction of temperature monitoring), this series introduces a new trip
> point type (THERMAL_TRIP_COLD) to indicate a trip point at which falling
> temperature monitoring must be triggered. This patch series uses Daniel
> Lezcano's recently added thermal genetlink interface[2] to notify userspace
> of falling temperature and rising temperature at the cold trip point. This
> will enable a user space engine to trigger the relevant mitigation for
> falling temperature. At present, no support is added to any of the thermal
> governors to monitor and mitigate falling temperature at the cold trip
> point;rather all governors return doing nothing if triggered for a cold
> trip point. As future extension, monitoring of falling temperature can be
> added to the relevant thermal governor. 

I agree we need a cold trip point in order to introduce the functioning
temperature range in the thermal framework.

Rui, what is your opinion ?



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[RFC PATCH 0/4] thermal: Introduce support for monitoring falling temperature

[Thara Gopinath]

Thermal framework today supports monitoring for rising temperatures and
subsequently initiating cooling action in case of a thermal trip point
being crossed. There are scenarios where a SoC need some warming action to
be activated if the temperature falls below a cetain permissible limit.
Since warming action can be considered mirror opposite of cooling action,
most of the thermal framework can be re-used to achieve this.

This patch series is yet another attempt to add support for monitoring
falling temperature in thermal framework. Unlike the first attempt[1]
(where a new property was added to thermal trip point binding to indicate
direction of temperature monitoring), this series introduces a new trip
point type (THERMAL_TRIP_COLD) to indicate a trip point at which falling
temperature monitoring must be triggered. This patch series uses Daniel
Lezcano's recently added thermal genetlink interface[2] to notify userspace
of falling temperature and rising temperature at the cold trip point. This
will enable a user space engine to trigger the relevant mitigation for
falling temperature. At present, no support is added to any of the thermal
governors to monitor and mitigate falling temperature at the cold trip
point;rather all governors return doing nothing if triggered for a cold
trip point. As future extension, monitoring of falling temperature can be
added to the relevant thermal governor. 

Patch series introducing various resources that are used as warming devices
on Qualcomm sdm845:
https://lkml.org/lkml/2019/7/29/749 (already merged)
https://lkml.org/lkml/2020/6/3/1112 (under review)

1.https://lkml.org/lkml/2019/9/18/1180
2.https://lkml.org/lkml/2020/7/6/238 

Thara Gopinath (4):
  dt-bindings:thermal:Add cold trip point type
  thermal: Add support for cold trip point
  thermal:core:Add genetlink notifications for monitoring falling
temperature
  thermal: Modify thermal governors to do nothing for "cold" trip points

 .../devicetree/bindings/thermal/thermal.txt   |  1 +
 drivers/thermal/gov_bang_bang.c   |  8 +++
 drivers/thermal/gov_fair_share.c  |  8 +++
 drivers/thermal/gov_power_allocator.c |  8 +++
 drivers/thermal/gov_step_wise.c   |  8 +++
 drivers/thermal/thermal_core.c| 21 +--
 drivers/thermal/thermal_of.c  |  1 +
 include/uapi/linux/thermal.h  |  1 +
 8 files changed, 50 insertions(+), 6 deletions(-)

-- 
2.25.1