linux-kernel - Re: [PATCH v4 01/20] PM / devfreq: exynos: Add generic exynos bus frequency driver

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Message-id: <567356B6.5030403@samsung.com>
Date:	Fri, 18 Dec 2015 09:43:34 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	myungjoo.ham@...sung.com, kgene@...nel.org
Cc:	kyungmin.park@...sung.com, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, linux@....linux.org.uk,
	tjakobi@...h.uni-bielefeld.de, linux.amoon@...il.com,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 01/20] PM / devfreq: exynos: Add generic exynos bus
 frequency driver

On 2015년 12월 18일 09:34, Chanwoo Choi wrote:
> Hi,
> 
> On 2015년 12월 15일 12:41, Krzysztof Kozlowski wrote:
>> On 14.12.2015 15:38, Chanwoo Choi wrote:
>>> This patch adds the generic exynos bus frequency driver for AMBA AXI bus
>>> of sub-blocks in exynos SoC with DEVFREQ framework. The Samsung Exynos SoC
>>> have the common architecture for bus between DRAM and sub-blocks in SoC.
>>> This driver can support the generic bus frequency driver for Exynos SoCs.
>>>
>>> In devicetree, Each bus block has a bus clock, regulator, operation-point
>>> and devfreq-event devices which measure the utilization of each bus block.
>>>
>>> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
>>> [linux.amoon: Tested on Odroid U3]
>>> Tested-by: Anand Moon <linux.amoon@...il.com>
>>> ---
>>>  drivers/devfreq/Kconfig             |  15 ++
>>>  drivers/devfreq/Makefile            |   1 +
>>>  drivers/devfreq/exynos/Makefile     |   1 +
>>>  drivers/devfreq/exynos/exynos-bus.c | 449 ++++++++++++++++++++++++++++++++++++
>>>  4 files changed, 466 insertions(+)
>>>  create mode 100644 drivers/devfreq/exynos/exynos-bus.c
>>>
>>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>>> index 64281bb2f650..55ec774f794c 100644
>>> --- a/drivers/devfreq/Kconfig
>>> +++ b/drivers/devfreq/Kconfig
>>> @@ -66,6 +66,21 @@ config DEVFREQ_GOV_USERSPACE
>>>  
>>>  comment "DEVFREQ Drivers"
>>>  
>>> +config ARM_EXYNOS_BUS_DEVFREQ
>>> +	bool "ARM EXYNOS Generic Memory Bus DEVFREQ Driver"
>>> +	depends on ARCH_EXYNOS
>>> +	select DEVFREQ_GOV_SIMPLE_ONDEMAND
>>> +	select DEVFREQ_EVENT_EXYNOS_PPMU
>>> +	select PM_DEVFREQ_EVENT
>>> +	select PM_OPP
>>> +	help
>>> +	  This adds the common DEVFREQ driver for Exynos Memory bus. Exynos
>>> +	  Memory bus has one more group of memory bus (e.g, MIF and INT block).
>>> +	  Each memory bus group could contain many memoby bus block. It reads
>>> +	  PPMU counters of memory controllers by using DEVFREQ-event device
>>> +	  and adjusts the operating frequencies and voltages with OPP support.
>>> +	  This does not yet operate with optimal voltages.
>>> +
>>>  config ARM_EXYNOS4_BUS_DEVFREQ
>>>  	bool "ARM Exynos4210/4212/4412 Memory Bus DEVFREQ Driver"
>>>  	depends on (CPU_EXYNOS4210 || SOC_EXYNOS4212 || SOC_EXYNOS4412) && !ARCH_MULTIPLATFORM
>>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>>> index 5134f9ee983d..375ebbb4fcfb 100644
>>> --- a/drivers/devfreq/Makefile
>>> +++ b/drivers/devfreq/Makefile
>>> @@ -6,6 +6,7 @@ obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
>>>  obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
>>>  
>>>  # DEVFREQ Drivers
>>> +obj-$(CONFIG_ARCH_EXYNOS)		+= exynos/
>>
>> Why limiting it to ARCH_EXYNOS? Are there real dependencies on exynos
>> mach code? Or on ARM code?
> 
> There is no dependency.
> 
>>
>> If not, then this probably should be obj-y to allow compile testing.
>> Particular objects would be selected by ARM_EXYNOS_BUS_DEVFREQ.
> 
> OK. I'll alter it as obj-y.

As you commented, CONFIG_ARM_EXYNOS_BUS_DEVFREQ is more appropriate
without exynos/ directory as following:

+obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)   += exynos-bus.o

Best Regards,
Chanwoo Choi
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