linux-kernel - Re: [PATCH v9 05/20] PM / devfreq: Add new passive governor

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Date:	Tue, 12 Apr 2016 09:30:34 +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 05/20] PM / devfreq: Add new passive governor

On 04/11/2016 05:57 AM, Chanwoo Choi wrote:
> This patch adds the new passive governor for DEVFREQ framework. The following
> governors are already present and used for DVFS (Dynamic Voltage and Frequency
> Scaling) drivers. The following governors are independently used for one device
> driver which don't give the influence to other device drviers and also don't
> receive the effect from other device drivers.
> - ondemand / performance / powersave / userspace
> 
> The passive governor depends on operation of parent driver with specific
> governos extremely and is not able to decide the new frequency by oneself.
> According to the decided new frequency of parent driver with governor,
> the passive governor uses it to decide the appropriate frequency for own
> device driver. The passive governor must need the following information
> from device tree:
> - the source clock and OPP tables
> - the instance of parent device
> 
> For exameple,
> there are one more devfreq device drivers which need to change their source
> clock according to their utilization on runtime. But, they share the same
> power line (e.g., regulator). So, specific device driver is operated as parent
> with ondemand governor and then the rest device driver with passive governor
> is influenced by parent device.
> 
> Suggested-by: Myungjoo Ham <myungjoo.ham@...sung.com>
> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> [tjakobi: Reported RCU locking issue and cw00.choi fix it]
> Reported-by: Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>
> [linux.amoon: Reported possible recursive locking and cw00.choi fix it]
> Reported-by: Anand Moon <linux.amoon@...il.com>
> Signed-off-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> ---
>  drivers/devfreq/Kconfig            |   8 ++
>  drivers/devfreq/Makefile           |   1 +
>  drivers/devfreq/governor_passive.c | 207 +++++++++++++++++++++++++++++++++++++
>  include/linux/devfreq.h            |  33 ++++++
>  4 files changed, 249 insertions(+)
>  create mode 100644 drivers/devfreq/governor_passive.c
> 

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

Best regards,
Krzysztof