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

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Date:	Fri, 11 Dec 2015 12:56:49 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Rob Herring <robh@...nel.org>
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 2015년 12월 11일 12:24, Rob Herring wrote:
> 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.

>From the H/W point of view, ISP block is really not included in ISP's AXI bus (bus_isp).
Just, the bus_isp connect to between ISP block and DRAM.

Thanks,
Chanwoo Choi

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