Message-ID: <1487694.oyLYSrbpA8@diego>
Date:	Wed, 10 Sep 2014 09:24:31 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	"edubezval@...il.com" <edubezval@...il.com>
Cc:	Zhang Rui <rui.zhang@...el.com>,
	Caesar Wang <caesar.wang@...k-chips.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Tao Huang <huangtao@...k-chips.com>,
	Eddie Cai <cf@...k-chips.com>,
	Douglas Anderson <dianders@...omium.org>,
	dtor <dtor@...omium.org>, Chris Zhong <zyw@...k-chips.com>,
	"addy.ke@...k-chips.com" <addy.ke@...k-chips.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	zhaoyifeng <zyf@...k-chips.com>
Subject: Re: [PATCH v4 2/4] dt-bindings: document Rockchip thermal

Am Dienstag, 9. September 2014, 21:14:18 schrieb edubezval@...il.com:
> Hello,
> 
> On Tue, Sep 9, 2014 at 9:02 PM, Zhang Rui <rui.zhang@...el.com> wrote:
> > On Tue, 2014-09-09 at 11:09 -0400, Eduardo Valentin wrote:
> >> Hello
> >> 
> >> On Tue, Sep 09, 2014 at 01:35:31PM +0200, Heiko Stübner wrote:
> >> > Am Dienstag, 9. September 2014, 10:27:17 schrieb Zhang Rui:
> >> > > On Thu, 2014-09-04 at 09:02 +0800, Caesar Wang wrote:
> >> > > > 在 2014年09月03日 16:07, Heiko Stübner 写道:
> >> > > > > Am Mittwoch, 3. September 2014, 10:10:37 schrieb Caesar Wang:
> >> > > > >> This add the necessary binding documentation for the thermal
> >> > > > >> found on Rockchip SoCs
> >> > > > >> 
> >> > > > >> Signed-off-by: zhaoyifeng <zyf@...k-chips.com>
> >> > > > >> Signed-off-by: Caesar Wang <caesar.wang@...k-chips.com>
> >> > > > >> ---
> >> > > > >> 
> >> > > > >>   .../devicetree/bindings/thermal/rockchip-thermal.txt | 20
> >> > > > >> 
> >> > > > >> ++++++++++++++++++++ 1 file changed, 20 insertions(+)
> >> > > > >> 
> >> > > > >>   create mode 100644
> >> > > > >> 
> >> > > > >> Documentation/devicetree/bindings/thermal/rockchip-thermal.txt
> >> > > > >> 
> >> > > > >> diff --git
> >> > > > >> a/Documentation/devicetree/bindings/thermal/rockchip-thermal.txt
> >> > > > >> b/Documentation/devicetree/bindings/thermal/rockchip-thermal.txt
> >> > > > >> new
> >> > > > >> file
> >> > > > >> mode 100644
> >> > > > >> index 0000000..1ed4d4c
> >> > > > >> --- /dev/null
> >> > > > >> +++
> >> > > > >> b/Documentation/devicetree/bindings/thermal/rockchip-thermal.tx
> >> > > > >> t
> >> > > > >> @@ -0,0 +1,20 @@
> >> > > > >> +* Temperature Sensor ADC (TSADC) on rockchip SoCs
> >> > > > >> +
> >> > > > >> +Required properties:
> >> > > > >> +- compatible: "rockchip,rk3288-tsadc"
> >> > > > >> +- reg: physical base address of the controller and length of
> >> > > > >> memory
> >> > > > >> mapped
> >> > > > >> +       region.
> >> > > > >> +- interrupts: The interrupt number to the cpu. The interrupt
> >> > > > >> specifier
> >> > > > >> format +           depends on the interrupt controller.
> >> > > > >> +- clocks: Must contain an entry for each entry in clock-names.
> >> > > > >> +- clock-names: Shall be "tsadc" for the converter-clock, and
> >> > > > >> "apb_pclk" for +            the peripheral clock.
> >> > > > > 
> >> > > > > You're using the passive-temp, critical-temp and force-shut-temp
> >> > > > > properties in your driver without declaring them here.
> >> > > > 
> >> > > > frankly,the about are need be declared. but  there are 4 types[0]
> >> > > > for
> >> > > > trip in thermal framework,
> >> > > > there is no force-shut for me. So I want to change it three
> >> > > > additional
> >> > > > properties in [PATCH V4 4/4],
> >> > > > 
> >> > > > 
> >> > > > [0]
> >> > > > {
> >> > > > 
> >> > > >      THERMAL_TRIP_CRITICAL,
> >> > > >      THERMAL_TRIP_HOT,
> >> > > >      THERMAL_TRIP_PASSIVE,
> >> > > >      THERMAL_TRIP_ACTIVE,
> >> > > > 
> >> > > > }
> >> > > 
> >> > > this sounds reasonable to me.
> >> > > 
> >> > > > > But more importantly, please use the generic trip-points for
> >> > > > > this. I
> >> > > > > guess it shouldn't be a problem to introduce a "forced-shutdown"
> >> > > > > trippoint [0] for the additional trip-point you have - thermal
> >> > > > > maintainers, please shout if I'm wrong :-)
> >> > > 
> >> > > what is the difference between a critical trip point and a
> >> > > "forced-shutdown" trip point?
> >> > > Thermal core will do a shutdown in case the critical trip point is
> >> > > triggered.
> >> > 
> >> > The forced-shutdown is where the thermal controller is supposed to also
> >> > do a>> 
> >> Currently, there is no discrimination between hardware configured /
> >> triggered thermal shutdown and software detected / triggered thermal
> >> shutdown. One way to implement it though is to reuse the critical trip
> >> type. Even if you use more than one trip type it is doable, it will
> >> depend on the priorities you give to software triggered and hardware
> >> triggered.
> >> 
> >> > shutdown in hardware. As you said the thermal core will also shutdown
> >> > at the critical trip point, I guess we could map Caesar's value like
> >> > 
> >> > trip-point          tsadc
> >> > critical            forced-shutdown (the 120 degrees in patch 4)
> >> > 
> >> > hot                 critical (the 100 degrees)
> >> > ...
> >> 
> >> In the case we are planing to expand the trip type range, adding one
> >> specific to hardware configurable shutdown makes sense to me too.
> > 
> > hmmm, why? you don't want an orderly shutdown? I still do not understand
> > why we need a hardware shutdown trip point.
> > Say, if we expect the system to be shutdown at 100C, I don't think we
> > have a chance to trigger the hardware shutdown trip point.
> > Further more, if my understanding is right, thermal core won't do
> > anything for the hardware shutdown trip point because the system will be
> > shutdown automatically, right? If this is true, why bother introducing
> > this to thermal core?
> 
> Some ICs allow configuring the temperature when the shutdown will
> happen. That is, you setup in registers the thermal shutdown
> threshold, and one of the output pin of the IC is wired to, say, the
> processor reset pin. Some other ICs have the threshold hardwired, and
> cannot be configured.
> 
> Those options are a last chance to avoid processors to burn, in case
> software really gets stuck at high temperatures.
> 
> The only thing that the thermal driver would need to worry is the
> configuration step, that is, writing the value to the registers. In
> the case the thermal core would have a specific trip type for such
> case, the core itself would not do anything, except allowing designing
> a thermal zone with hardware shutdown trips. And thus the thermal
> driver would do the configuration.
> 
> 
> Currently, the way I see to implement this is to interpret critical
> trips as the threshold to be configured at the IC registers. That is,
> reusing critical trips as orderly power down and as the hardware
> shutdown threshold.

which was what I also meant to express above [but seemingly failed to do 
properly :-) ].

Critical is specified as "Hardware not reliable", so I'd think it wouldn't 
matter how the hw is shut down (orderly/unorderly) as long as its done.
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