linux-kernel - Re: [RFC PATCH 09/15] PM / devfreq: exynos: Update documentation for bus devices using passive governor

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Date:	Mon, 30 Nov 2015 15:14:53 -0600
From:	Rob Herring <robh@...nel.org>
To:	Chanwoo Choi <cw00.choi@...sung.com>
Cc:	myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
	kgene@...nel.org, k.kozlowski@...sung.com, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, linux@....linux.org.uk,
	tjakobi@...h.uni-bielefeld.de, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [RFC PATCH 09/15] PM / devfreq: exynos: Update documentation for
 bus devices using passive governor

On Thu, Nov 26, 2015 at 10:47:33PM +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     | 226 ++++++++++++++++++++-
>  1 file changed, 223 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> index 5d90623bd173..c4a6fe30075e 100644
> --- a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> @@ -12,18 +12,23 @@ 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.
>  
> @@ -32,7 +37,19 @@ 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 block (dmc clock)
> +	- MIF (Memory Interface) block
> +	: VDD_MIF |--- DMC
> +
> +	- INT (Internal) block
> +	: VDD_INT |--- LEFTBUS  |--- PERIL
> +		  |    (parent) |--- MFC
> +		  |             |--- G3D
> +		  |
> +		  |--- RIGHTBUS |--- FSYS
> +				|--- LCD0
> +				|--- PERIR
> +				|--- ISP
> +				|--- CAM

I would expect the DT to mirror this topology which doesn't seem to be 
the case in the example.


>  	- MIF bus's frequency/voltage table
>  	-----------------------
> @@ -45,6 +62,20 @@ Example1:
>  	|L5| 400000 |875000   |
>  	-----------------------
>  
> +	- INT bus's frequency/voltage table
> +	-----------------------------------------------------------------------
> +	|Lv| Freq                                                   | Voltage |
> +	-----------------------------------------------------------------------
> +	|  |LEFTBUS|RIGHTBUS|LCD0   |FSYS   |MCUISP |ISP    |PERIL  |VDD_INT  |
> +	|  |*parent|passive |passive|passive|passive|passive|passive|         |
> +	-----------------------------------------------------------------------
> +	|L1|50000  |50000   |50000  |50000  |50000  |50000  |50000  |900000   |
> +	|L2|80000  |80000   |80000  |80000  |80000  |80000  |80000  |900000   |
> +	|L3|100000 |100000  |100000 |100000 |100000 |100000 |100000 |1000000  |
> +	|L4|133000 |133000  |133000 |133000 |200000 |200000 |       |1000000  |
> +	|L5|200000 |200000  |200000 |200000 |400000 |300000 |       |1000000  |
> +	-----------------------------------------------------------------------

Do you really have 5 states? It look like there are 2 to me because the 
OPP tables only really need to have the max freq at each voltage point. 

Rob
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