linux-kernel - Re: [PATCHv2 8/8] devfreq: exynos4: Add busfreq driver for exynos4210/exynos4x12

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Message-ID: <20140313175308.GE25870@e106331-lin.cambridge.arm.com>
Date:	Thu, 13 Mar 2014 17:53:08 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Chanwoo Choi <cw00.choi@...sung.com>
Cc:	"myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
	"kyungmin.park@...sung.com" <kyungmin.park@...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 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?

> +- reg		: offset and length of the ppmudmc0/1
> +		  - PPMU (Performance Profiling Monitoring Units)

You seem to require a particular order here. It would be good to be
explicit about it.

> +		  : It is to profile performance event of DMC(Dynamic Memory
> +		  Controller) So, exynos4_bus.c can check memory bus utilization
> +		  by using PPMU of Exynos4 SoC.

This is superfluous, and Linux-specific. The binding document shouldn't
need to refer to drivers.

> +- clocks	: clock number of ppmudmc0/1
> +- clock-names	: clock name of ppmudmc0/1

Are these two clocks, or one clock with a slash in the name?

Please list each name separately.

> +- vdd_int-supply: regulator for interface block of Exynos4
> +
> +Optional properties:
> +- vdd_mif-supply: regulator for DMC block of Exynos4x12 if Exynos4x12 Soc
> +- regs-name	: register name of ppmudmc0/1

This is completely nonstandard. Did you mean reg-names?

Please be explicit about the names you expect. Write them in full,
quoted, and describe the relationship to the reg property.

> +
> +All the required listed above must be defined under code busfreq with devfreq

I'm having some difficulty figuring out what exactly this is intended to
mean.

Thanks,
Mark.
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