linux-kernel - Re: [PATCH v9 07/20] PM / devfreq: exynos: Update documentation for bus devices using passive governor

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Date:	Tue, 12 Apr 2016 09:34:34 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Chanwoo Choi <cw00.choi@...sung.com>, myungjoo.ham@...sung.com,
	kyungmin.park@...sung.com, kgene@...nel.org,
	s.nawrocki@...sung.com, tomasz.figa@...il.com
Cc:	rjw@...ysocki.net, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, linux@....linux.org.uk,
	linux.amoon@...il.com, m.reichl@...etechno.de,
	tjakobi@...h.uni-bielefeld.de, inki.dae@...sung.com,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v9 07/20] PM / devfreq: exynos: Update documentation for
 bus devices using passive governor

On 04/11/2016 05:57 AM, 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>
> Acked-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> ---
>  .../devicetree/bindings/devfreq/exynos-bus.txt     | 250 ++++++++++++++++++++-
>  1 file changed, 247 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> index 78171b918e3f..03f13d38f1a1 100644
> --- a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> @@ -8,22 +8,46 @@ of the bus in runtime. To monitor the usage of each bus in runtime,
>  the driver uses the PPMU (Platform Performance Monitoring Unit), which
>  is able to measure the current load of sub-blocks.
>  
> +The Exynos SoC includes the various sub-blocks which have the each AXI bus.
> +The each AXI bus has the owned source clock but, has not the only owned
> +power line. The power line might be shared among one more sub-blocks.
> +So, we can divide into two type of device as the role of each sub-block.
> +There are two type of bus devices as following:
> +- parent bus device
> +- passive bus device
> +
> +Basically, parent and passive bus device share the same power line.
> +The parent bus device can only change the voltage of shared power line
> +and the rest bus devices (passive bus device) depend on the decision of
> +the parent bus device. If there are three blocks which share the VDD_xxx
> +power line, Only one block should be parent device and then the rest blocks
> +should depend on the parent device as passive device.
> +
> +	VDD_xxx |--- A block (parent)
> +		|--- B block (passive)
> +		|--- C block (passive)
> +
>  There are a little different composition among Exynos SoC because each Exynos
>  SoC has different sub-blocks. Therefore, shch difference should be specified

s/shch/such/

>  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.
>  - operating-points-v2: the OPP table including frequency/voltage information
>    to support DVFS (Dynamic Voltage/Frequency Scaling) feature.
> +
> +Required properties only for parent bus device:
>  - vdd-supply: the regulator to provide the buses with the voltage.
>  - devfreq-events: the devfreq-event device to monitor the current utilization
>    of buses.
>  
> -Optional properties for bus device:
> +Required properties only for passive bus device:
> +- devfreq: the parent bus device.
> +
> +Optional properties only for parent bus device:
>  - exynos,saturation-ratio: the percentage value which is used to calibrate
>  			the performance count against total cycle count.
>  - exynos,voltage-tolerance: the percentage value for bus voltage tolerance
> @@ -34,7 +58,20 @@ 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.

s/regualtor/regulator/


Acked-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

Best regards,
Krzysztof