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Message-id: <54BE3E10.2080906@samsung.com>
Date: Tue, 20 Jan 2015 20:37:52 +0900
From: Chanwoo Choi <cw00.choi@...sung.com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Rob Herring <robherring2@...il.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 01/20/2015 08:22 PM, Viresh Kumar wrote:
> On 20 January 2015 at 13:53, Chanwoo Choi <cw00.choi@...sung.com> wrote:
>> But, the frequency of OPPs is only used for devfreq ondemand governor.
>> After deciding the proper frequency of memory bus on ondemand governor,
>> exynos-bus.c (exynos memory bus frequency driver) use the frequency table
>> of memory bus blocks on below to change the clock rate of memory bus block.
>
>> Firs of all,
>> I explain the hierarchy of Exynos memory buses.
>>
>> For example of Exynos3250 memory bus,
>> This patch divide the memory bus group according to power rail (regulator).
>> - MIF (Memory Interface ) memory bus group uses the VDD_MIF regulator.
>> - INT (Internal) memory bus group uses the VDD_INT regulator.
>>
>> Each memory bus group contains only one power rail(regulator) and one more memory bus blocks as follwing:
>>
>> - MIF memory bus group
>> power rail(VDD_MIF)-->|--- memory bus for DMC (Dynamic Memory Controller) block (dmc clock)
>>
>> - INT memory bus group
>> |--- memory bus for PERI block (aclk_100 clock)
>> |
>> |--- memory bus for DISPLAY block (aclk_160 clock)
>> |
>> |--- memory bus for ISP block (aclk_200 clock)
>> |
>> |--- memory bus for GPS block (aclk_266 clock)
>> power rail(VDD_INT)-->|
>> |--- memory bus for MCUISP block (aclk_400_mcuisp clock)
>> |
>> |--- memory bus for Leftbus block (gdl clock)
>> |
>> |--- memory bus for Rightbus block (gdr clock)
>> |
>> |--- memory bus for MFC block (mfc clock)
>>
>>
>> Exynos3250 has following table for INT memory bus group:
>> All clocks of INT memory bus group have to contain the same entry count
>> againt the number of 'virtual freqw'. So, each memory bus clock could have duplicate clocks.
>>
>> ------------------------------------------------------------------------
>> Level|virtual freq|PERI's clk|Display's clk|ISP's clk|GPS's clk| voltage|
>> ------------------------------------------------------------------------
>> L6 |400000 |100000 |200000 |200000 |300000 | 95000 |
>> L5 |200000 |100000 |160000 |200000 |200000 | 95000 |
>> L4 |133000 |100000 |100000 |100000 |133000 | 92500 |
>> L3 |100000 |100000 |80000 |80000 |100000 | 85000 |
>> L2 |80000 |50000 |80000 |50000 |50000 | 85000 |
>> L1 |50000 |50000 |50000 |50000 |50000 | 85000 |
>> -------------------------------------------------------------------------
>> (Except for mcuisp, leftbus, rightbus, mfc block)
>>
>> This table is used for devfreq ondemand governor as following:
>> 1. ondemand governor in devfreq use the 'virtual freq' to devcide the proper
>> frequency for memory bus.
>> 2. ondemand governor executes the *_target() function to set clock rate and voltage.
>> 3. *_target() function in exynos-bus.c changes the clock rate of {PERIS|Display|ISP|GPS} clk
>> according to decided 'Level' by devfreq ondemand governor.
>
> I see..
>
> Please confirm if my understanding is correct.
> - mem-bus-group: all blocks sharing a regulator
> - mem-bus-block: individual blocks managing their clock rate
Right and mem-bus-blcoks are included in a mem-bus-group.
>
> What you do in kernel is register group as a device (with virtual OPPs)
> and then manage blocks within the driver. And so you need to do this
> dummy mapping of virtual to physical frequencies.
Right.
>
> It *may* not have done it this way, if I was to design this driver.
>
> Each bus-block is a separately controllable device and so must be registered
> separately. In that case all bus-blocks will have separate OPP tables and
> all this dummy-v2p mapping will go away.
If each bus-block has separate regulator independently, each bus-block can be registered
separately. But, exynos bus-blocks in mem-bus-group share the same regulator.
>
> I believe that you are over complicating stuff without any need..
>
> --
> viresh
>
Best Regards,
Chanwoo Choi
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