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Date: Sat, 15 Mar 2014 20:36:13 +0900 From: Kyungmin Park <kmpark@...radead.org> To: Tomasz Figa <t.figa@...sung.com> Cc: Chanwoo Choi <cw00.choi@...sung.com>, Mark Rutland <mark.rutland@....com>, "myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>, "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>, "nm@...com" <nm@...com>, "b.zolnierkie@...saung.com" <b.zolnierkie@...saung.com>, Pawel Moll <Pawel.Moll@....com>, "swarren@...dotorg.org" <swarren@...dotorg.org>, "ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>, "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-samsung-soc@...r.kernel.org" <linux-samsung-soc@...r.kernel.org>, "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org> Subject: Re: [PATCHv2 8/8] devfreq: exynos4: Add busfreq driver for exynos4210/exynos4x12 On Sat, Mar 15, 2014 at 2:35 AM, Tomasz Figa <t.figa@...sung.com> wrote: > Hi Chanwoo, Mark, > > > On 14.03.2014 11:56, Chanwoo Choi wrote: >> >> Hi Mark, >> >> On 03/14/2014 07:35 PM, Mark Rutland wrote: >>> >>> On Fri, Mar 14, 2014 at 07:14:37AM +0000, Chanwoo Choi wrote: >>>> >>>> Hi Mark, >>>> >>>> On 03/14/2014 02:53 AM, Mark Rutland wrote: >>>>> >>>>> On Thu, Mar 13, 2014 at 08:17:29AM +0000, Chanwoo Choi wrote: >>>>>> >>>>>> This patch add busfreq driver for Exynos4210/Exynos4x12 memory >>>>>> interface >>>>>> and bus to support DVFS(Dynamic Voltage Frequency Scaling) according >>>>>> to PPMU >>>>>> counters. PPMU (Performance Profiling Monitorings Units) of Exynos4 >>>>>> SoC provides >>>>>> PPMU counters for DMC(Dynamic Memory Controller) to check memory bus >>>>>> utilization >>>>>> and then busfreq driver adjusts dynamically the operating >>>>>> frequency/voltage >>>>>> by using DEVFREQ Subsystem. >>>>>> >>>>>> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com> >>>>>> --- >>>>>> .../devicetree/bindings/devfreq/exynos4_bus.txt | 49 >>>>>> ++++++++++++++++++++++ >>>>>> 1 file changed, 49 insertions(+) >>>>>> create mode 100644 >>>>>> Documentation/devicetree/bindings/devfreq/exynos4_bus.txt >>>>>> >>>>>> diff --git a/Documentation/devicetree/bindings/devfreq/exynos4_bus.txt >>>>>> b/Documentation/devicetree/bindings/devfreq/exynos4_bus.txt >>>>>> new file mode 100644 >>>>>> index 0000000..2a83fcc >>>>>> --- /dev/null >>>>>> +++ b/Documentation/devicetree/bindings/devfreq/exynos4_bus.txt >>>>>> @@ -0,0 +1,49 @@ >>>>>> + >>>>>> +Exynos4210/4x12 busfreq driver >>>>>> +----------------------------- >>>>>> + >>>>>> +Exynos4210/4x12 Soc busfreq driver with devfreq for Memory bus >>>>>> frequency/voltage >>>>>> +scaling according to PPMU counters of memory controllers >>>>>> + >>>>>> +Required properties: >>>>>> +- compatible : should contain Exynos4 SoC type as follwoing: >>>>>> + - "samsung,exynos4x12-busfreq" for Exynos4x12 >>>>>> + - "samsung,exynos4210-busfreq" for Exynos4210 >>>>> >>>>> >>>>> Is there a device called "busfreq"? What device does this binding >>>>> describe? >>>> >>>> >>>> I'll add detailed description of busfreq as following: >>>> >>>> "busfreq(bus frequendcy)" driver means that busfreq driver control >>>> dynamically >>>> memory bus frequency/voltage by checking memory bus utilization to >>>> optimize >>>> power-consumption. When checking memeory bus utilization, >>>> exynos4_busfreq driver >>>> would use PPMU(Performance Profiling Monitoring Units). >>> >>> >>> This still sounds like a description of the _driver_, not the _device_. >>> The binding should describe the hardware, now the high level abstraction >>> that software is going to build atop of it. >>> >>> It sounds like this is a binding for the DMC PPMU? >>> >>> Is the PPMU a component of the DMC, or is it bolted on the side? >> >> >> PPMU(Performance Profiling Monitoring Unit) is to profile performance >> event of >> various IP on Exynos4. Each PPMU provide perforamnce event for each IP. >> We can check various PPMU as following: >> >> PPMU_3D >> PPMU_ACP >> PPMU_CAMIF >> PPMU_CPU >> PPMU_DMC0 >> PPMU_DMC1 >> PPMU_FSYS >> PPMU_IMAGE >> PPMU_LCD0 >> PPMU_LCD1 >> PPMU_MFC_L >> PPMU_MFC_R >> PPMU_TV >> PPMU_LEFT_BUS >> PPMU_RIGHT_BUS >> >> DMC (Dynamic Memory Controller) control the operation of DRAM in Exynos4 >> SoC. >> If we need to get memory bust utilization of DMC, we can get memory bus >> utilization >> from PPMU_DMC0/PPMU_DMC1. >> >> So, Exynos4's busfreq used two(PPMU_DMC0/PPMU_DMC1) among upper various >> PPMU list. > > > Well, PPMUs and DMCs are separate hardware blocks found inside Exynos SoCs. > Busfreq/devfreq is just a Linux-specific abstraction responsible for > collecting data using PPMUs and controlling frequencies and voltages of > appropriate power planes, vdd_int responsible for powering DMC0 and DMC1 > blocks in this case. > > I'm afraid that the binding you're proposing is unfortunately incorrect, > because it represents the software abstraction, not the real hardware. > > Instead, this should be separated into several independent bindings: > > - PPMU bindings to list all the PPMU instances present in the SoC and > resources they need, > > - power plane bindings, which define a power plane in which multiple IP > blocks might reside, can be monitored by one or more PPMU units and > frequency and voltage of which can be configured according to determined > performance level. Needed resources will be clocks and regulators to scale > and probably also operating points. > > Then, exynos-busfreq driver should bind to such power planes, parse > necessary data from DT (list of PPMUs and IP blocks, clocks, regulators and > operating points) and register a devfreq entity. How about to use component DT like DRM? > > Best regards, > Tomasz > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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