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Re: [PATCH v4 2/2] dt: power: st: Provide bindings for ST's OPPs

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  Re: [PATCH v4 2/2] dt: power: st: Provide bindings for ST's OPPs Lee Jones <lee.jones@linaro.org> - 2015-07-28 09:40 +0200
    Re: [PATCH v4 2/2] dt: power: st: Provide bindings for ST's OPPs Viresh Kumar <viresh.kumar@linaro.org> - 2015-07-28 09:50 +0200
      Re: [PATCH v4 2/2] dt: power: st: Provide bindings for ST's OPPs Lee Jones <lee.jones@linaro.org> - 2015-07-28 10:40 +0200

#1193822 — Re: [PATCH v4 2/2] dt: power: st: Provide bindings for ST's OPPs

On Tue, 28 Jul 2015, Viresh Kumar wrote:

> Cc'ing few people (whom I cc'd last time as well :)).
> 
> On 27-07-15, 16:20, Lee Jones wrote:
> > These OPPs are used in ST's CPUFreq implementation.
> > 
> > Signed-off-by: Lee Jones <lee.jones@linaro.org>
> > ---
> > 
> > Changelog:
> >  - None, new patch
> > 
> >  Documentation/devicetree/bindings/power/opp-st.txt | 76 ++++++++++++++++++++++
> >  1 file changed, 76 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/power/opp-st.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/power/opp-st.txt b/Documentation/devicetree/bindings/power/opp-st.txt
> > new file mode 100644
> > index 0000000..6eb2a91
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/power/opp-st.txt
> > @@ -0,0 +1,76 @@
> > +STMicroelectronics OPP (Operating Performance Points) Bindings
> > +--------------------------------------------------------------
> > +
> > +Frequency Scaling only
> > +----------------------
> > +
> > +Located in CPU's node:
> > +
> > +- operating-points	: [See: ./opp.txt]
> > +
> > +Example [safe]
> > +--------------
> > +
> > +cpus {
> > +	cpu@0 {
> > +				 /* kHz     uV   */
> > +		operating-points = <1500000 0
> > +				    1200000 0
> > +				    800000  0
> > +				    500000  0>;
> > +	};
> > +};
> > +
> > +Dynamic Voltage and Frequency Scaling (DVFS)
> > +--------------------------------------------
> > +
> > +Located in 'cpu0-opp-list' node [to be provided ONLY by the bootloader]:
> > +
> > +- compatible		: Should be "operating-points-v2-sti"
> > +- opp{1..N} 		: Each 'oppX' subnode will contain the following properties:
> 
> Or should we mention:
> - opp{1..N} 		: Each 'oppX' subnode shall contain below properties,
>                           over what ./opp.txt defines:
> 
> ?

I disagree.  For one, only 'opp-hz' is defined in ./opp.tx.  Secondly
it would be annoying to have to have to keep jumping between documents
to obtain the whole picture.  Finally, generic bindings are repeated
in platform/device specific documentation all the time.  Grep for
'clocks' or 'regulator-* or 'interrupts' or 'reg' or 'clock-frequency'
(which IMHO I think you should have used instead of 'opp-hz', but
that's by the by), or any number of other generic properties.

> > + - opp-hz		: CPU frequency [Hz] for this OPP [See: ./opp.txt]
> > + - st,avs		: List of available voltages [uV] indexed by process code
> > + - st,cuts		: Cut version this OPP is suitable for [0xFF means ALL]
> > + - st,substrate		: Substrate version this OPP is suitable for [0xFF means ALL]
> > +- st,syscfg		: Phandle to Major number register
> > +				First cell: offset to major number
> > +- st,syscfg-eng		: Phandle to Minor number and Pcode registers
> > +				First cell: offset to process code
> > +				Second cell: offset to minor number
> > +
> > +WARNING: The opp{1..N} nodes will be provided by the bootloader.  Do not attempt to
> > +	 artificially synthesise the opp{1..N} nodes or any of their descendants.
> > +	 They are very platform specific and may damage the hardware if created
> > +	 incorrectly.
> > +
> > +Example [unsafe]
> > +----------------
> > +
> > +cpus {
> > +	cpu@0 {
> > +		operating-points-v2	= <&cpu0_opp_list>;
> > +	};
> > +};
> > +
> > +/* ############################################################ */
> > +/* # WARNING: Do not attempt to copy/replicate this node,     # */
> > +/* #          it is only to be supplied by the bootloader !!! # */
> > +/* ############################################################ */
> > +cpu0-opp-list {
> > +	compatible	= "operating-points-v2-sti";
> > +	st,syscfg	= <&syscfg [major_offset]>;
> > +	st,syscfg-eng   = <&syscfg_eng [pcode_offset] [minor_offset]>;
> > +
> > +	opp0 {
> > +		opp-hz		= <1200000000>;
> > +		st,avs		= <1110 1150 1100 1080 1040 1020 980 930>;
> > +		st,substrate	= <0xff>;
> > +		st,cuts		= <0xff>;
> > +	};
> > +	opp1 {
> > +		opp-hz		= <1500000000>;
> > +		st,avs		= <1200 1200 1200 1200 1170 1140 1100 1070>;
> > +		st,substrate	= <0xff>;
> > +		st,cuts		= <0x2>;
> > +	};
> > +};
> 
> I don't see more problems here, unless we can move some of this to the
> generic bindings.
> 
> @Rob/Stephen: Please respond before it is late :)

No one knows this stuff better than you.  If you can't think of an
already existing binding that could suit to portray our 'cuts' and
'substrate' information (with a similar way to support our "all cuts"
and "all substrates" options, then there probably isn't one. ;)

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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#1193837

On 28-07-15, 08:34, Lee Jones wrote:
> I disagree.  For one, only 'opp-hz' is defined in ./opp.tx.  Secondly

There are other properties in op.txt like turbo, opp-suspend, latency,
etc.. which can be useful for your platform to. Its not used for now
is a different thing.

> it would be annoying to have to have to keep jumping between documents
> to obtain the whole picture.  Finally, generic bindings are repeated
> in platform/device specific documentation all the time.  Grep for
> 'clocks' or 'regulator-* or 'interrupts' or 'reg' or 'clock-frequency'

Yeah, I agree. I am not against that. What I meant to say was that its
an extension to opp-v2. So whatever is present in opp-v2 can be used
by ST's driver, without mentioning that here as well.

> (which IMHO I think you should have used instead of 'opp-hz', but
> that's by the by), or any number of other generic properties.

Hmm, probably yes. See I don't know everything :)

> > @Rob/Stephen: Please respond before it is late :)
> 
> No one knows this stuff better than you.  If you can't think of an
> already existing binding that could suit to portray our 'cuts' and
> 'substrate' information (with a similar way to support our "all cuts"
> and "all substrates" options, then there probably isn't one. ;)

Oh, I wasn't saying that there is an existing binding for supporting
your case. But if we want to move the cuts property to the generic
bindings so that others can use it. :)

-- 
viresh
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#1193880

On Tue, 28 Jul 2015, Viresh Kumar wrote:

> On 28-07-15, 08:34, Lee Jones wrote:
> > I disagree.  For one, only 'opp-hz' is defined in ./opp.tx.  Secondly
> 
> There are other properties in op.txt like turbo, opp-suspend, latency,
> etc.. which can be useful for your platform to. Its not used for now
> is a different thing.
> 
> > it would be annoying to have to have to keep jumping between documents
> > to obtain the whole picture.  Finally, generic bindings are repeated
> > in platform/device specific documentation all the time.  Grep for
> > 'clocks' or 'regulator-* or 'interrupts' or 'reg' or 'clock-frequency'
> 
> Yeah, I agree. I am not against that. What I meant to say was that its
> an extension to opp-v2. So whatever is present in opp-v2 can be used
> by ST's driver, without mentioning that here as well.
> 
> > (which IMHO I think you should have used instead of 'opp-hz', but
> > that's by the by), or any number of other generic properties.
> 
> Hmm, probably yes. See I don't know everything :)
> 
> > > @Rob/Stephen: Please respond before it is late :)
> > 
> > No one knows this stuff better than you.  If you can't think of an
> > already existing binding that could suit to portray our 'cuts' and
> > 'substrate' information (with a similar way to support our "all cuts"
> > and "all substrates" options, then there probably isn't one. ;)
> 
> Oh, I wasn't saying that there is an existing binding for supporting
> your case. But if we want to move the cuts property to the generic
> bindings so that others can use it. :)

Okay, so what are we waiting for before you'd be prepared to Ack the
binding?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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