linux-kernel - Re: [PATCH v2 09/19] PM / devfreq: exynos: Update documentation for bus devices using passive governor

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Message-ID: <20151211032417.GA22249@rob-hp-laptop>
Date:	Thu, 10 Dec 2015 21:24:17 -0600
From:	Rob Herring <robh@...nel.org>
To:	cw00.choi@...sung.com
Cc:	"myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
	Krzysztof Kozłowski <k.kozlowski@...sung.com>,
	Kukjin Kim <kgene@...nel.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	tjakobi@...h.uni-bielefeld.de, linux.amoon@...il.com,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 09/19] PM / devfreq: exynos: Update documentation for
 bus devices using passive governor

On Fri, Dec 11, 2015 at 12:10:13AM +0900, Chanwoo Choi wrote:
> On Thu, Dec 10, 2015 at 11:21 PM, Rob Herring <robh@...nel.org> wrote:
> > On Wed, Dec 09, 2015 at 01:08:01PM +0900, Chanwoo Choi wrote:
> >> This patch updates the documentation for passive bus devices and adds the
> >> detailed example of Exynos3250.
> >>
> >> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> >> ---
> >>  .../devicetree/bindings/devfreq/exynos-bus.txt     | 244 ++++++++++++++++++++-
> >>  1 file changed, 241 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> >> index 54a1f9c46c88..c4fdc70f8eac 100644
> >> --- a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> >> +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> >> @@ -13,18 +13,23 @@ SoC has the different sub-blocks. So, this difference should be specified
> >>  in devicetree file instead of each device driver. In result, this driver
> >>  is able to support the bus frequency for all Exynos SoCs.
> >>
> >> -Required properties for bus device:
> >> +Required properties for all bus devices:
> >>  - compatible: Should be "samsung,exynos-bus".
> >>  - clock-names : the name of clock used by the bus, "bus".
> >>  - clocks : phandles for clock specified in "clock-names" property.
> >>  - #clock-cells: should be 1.
> >>  - operating-points-v2: the OPP table including frequency/voltage information
> >>    to support DVFS (Dynamic Voltage/Frequency Scaling) feature.
> >> +
> >> +Required properties for only parent bus device:
> >>  - vdd-supply: the regulator to provide the buses with the voltage.
> >>  - devfreq-events: the devfreq-event device to monitor the curret utilization
> >>    of buses.
> >>
> >> -Optional properties for bus device:
> >> +Required properties for only passive bus device:
> >> +- devfreq: the parent bus device.
> >> +
> >> +Optional properties for only parent bus device:
> >>  - exynos,saturation-ratio: the percentage value which is used to calibrate
> >>                     the performance count againt total cycle count.
> >>
> >> @@ -33,7 +38,20 @@ Example1:
> >>       power line (regulator). The MIF (Memory Interface) AXI bus is used to
> >>       transfer data between DRAM and CPU and uses the VDD_MIF regualtor.
> >>
> >> -     - power line(VDD_MIF) --> bus for DMC (Dynamic Memory Controller) block
> >> +     - MIF (Memory Interface) block
> >> +     : VDD_MIF |--- DMC (Dynamic Memory Controller)
> >> +
> >> +     - INT (Internal) block
> >> +     : VDD_INT |--- LEFTBUS (parent device)
> >> +               |--- PERIL
> >> +               |--- MFC
> >> +               |--- G3D
> >> +               |--- RIGHTBUS
> >> +               |--- FSYS
> >> +               |--- LCD0
> >> +               |--- PERIR
> >> +               |--- ISP
> >> +               |--- CAM
> >
> > This still has the same problem as before. I would expect that the bus
> > hierarchy in the dts match the hierarchy here. You just have flat nodes
> > in the example below. So all IP blocks affected by frequency scaling
> > should be under the bus node defining the OPPs. Something like this:
> 
> The each bus of sub-block has not h/w dependency among sub-blocks
> and has the owned source clock / OPP table. Just they share the same
> power line. So, I think that flat nodes in the example below is not problem.

I'm talking about the peripherals not described here. Is the ISP block 
not a child of the bus_isp node? Same for the display controller block 
and bus_lcd0. And so on.

Rob

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