linux-kernel - Re: [PATCHv3 2/8] devfreq: exynos: Add documentation for generic exynos memory bus frequency driver

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Message-ID: <CAKohpomqosqxeDANC=NLBVmOUHyUoqd7Zhph7r6f7+ufYN48EQ@mail.gmail.com>
Date:	Tue, 20 Jan 2015 12:49:15 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Rob Herring <robherring2@...il.com>
Cc:	Chanwoo Choi <cw00.choi@...sung.com>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Kukjin Kim <kgene@...nel.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
	Mark Rutland <mark.rutland@....com>, a.kesavan@...sung.com,
	Tomasz Figa <tomasz.figa@...il.com>,
	Krzysztof Kozłowski <k.kozlowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Rob Herring <robh+dt@...nel.org>,
	InKi Dae <inki.dae@...sung.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCHv3 2/8] devfreq: exynos: Add documentation for generic
 exynos memory bus frequency driver

On 9 January 2015 at 02:48, Rob Herring <robherring2@...il.com> wrote:
> Adding Viresh.

Sorry for being too late, I was very busy with other cpufreq stuff I was doing
and saved this thread for later as it required me to understand it properly..

>> +Required properties for memory bus block:
>> +- clock-names : the name of clock used by the memory bus, "memory-bus".
>> +- clocks : phandles for clock specified in "clock-names" property.
>> +- #clock-cells: should be 1.
>> +- frequency: the frequency table to support DVFS feature.
>
> So you have just defined a new OPP table format. We already have one
> and Viresh is working to create a more extendable one. He asked about
> what's needed in devfreq, so Viresh here you go. :)

I failed to understand what's new here, probably I need more clarity on
what we are doing here..

So, this is what I see from OPPs point of view, everything else stripped out.

>> +       memory_bus_int: memory_bus@1 {

>> +               operating-points = <
>> +                       400000 950000
>> +                       200000 950000
>> +                       133000 925000
>> +                       100000 850000
>> +                       80000  850000
>> +                       50000  850000>;

So these are the OPPs your "groups" support and below ones are
the frequencies that each block will support. Right ?

>> +               blocks {

>> +                               frequency = <
>> +                                       100000
>> +                                       100000
>> +                                       100000
>> +                                       100000

Why this replication here ?

>> +                                       50000
>> +                                       50000>;
>> +                       };

How are the above two tables (operating-points and frequency) related
here? What about the voltages at which these frequencies are possible ?

>> +                       display_block: memory_bus_block2 {

>> +                               frequency = <
>> +                                       200000
>> +                                       160000
>> +                                       100000
>> +                                       80000
>> +                                       80000
>> +                                       50000>;
>> +                       };

>> +                       isp_block: memory_bus_block3 {

>> +                               frequency = <
>> +                                       200000
>> +                                       200000
>> +                                       100000
>> +                                       80000
>> +                                       50000
>> +                                       50000>;
>> +                       };

>> +                       gps_block: memory_bus_block4 {

>> +                               frequency = <
>> +                                       300000
>> +                                       200000
>> +                                       133000
>> +                                       100000
>> +                                       50000
>> +                                       50000>;
>> +                       };

same for others as well..
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