Re: Re: [PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[MyungJoo Ham <myungjoo.ham@samsung.com>]

>  
> Dear Myungjoo,
>
>On 01/13/2015 05:42 PM, MyungJoo Ham wrote:
>>>   
>>>  This patch adds the generic exynos bus frequency driver for memory bus
>>> with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
>>> for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
>>> support the memory bus frequency driver for Exynos SoCs.
>>>
>>> Each memory bus block has a clock for memory bus speed and frequency
>>> table which is changed according to the utilization of memory bus on runtime.
>>> And then each memory bus group has the one more memory bus blocks and
>>> OPP table (including frequency and voltage), regulator, devfreq-event
>>> devices.
>>>
>>> There are a little difference about the number of memory bus because each Exynos
>>> SoC have the different sub-IP and different memory bus speed. In spite of this
>>> difference among Exynos SoCs, we can support almost Exynos SoC by adding
>>> unique data of memory bus to devicetree file.
>>>
>>> Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
>>> Cc: Kyungmin Park <kyungmin.park@samsung.com>
>>> Cc: Kukjin Kim <kgene@kernel.org>
>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>> ---
>>>  drivers/devfreq/Kconfig          |  15 +
>>>  drivers/devfreq/Makefile         |   1 +
>>>  drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 605 insertions(+)
>>>  create mode 100644 drivers/devfreq/exynos-busfreq.c
>> 
>> Exynos drivers are located at drivers/devfreq/exynos/
>> Please relocate/rename exynos-busfreq.c
>
>OK. I'll move it at drivers/devfreq/exynos directory.
>Do you prefer 'exynos-bus.c' instead of 'exynos-busfreq.c'?
>If you reply, I'll change it.

exynos-bus looks more pretty :)

>
>> 
>> []
>> 
>>> diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
>>> new file mode 100644
>>> index 0000000..b180f43
>>> --- /dev/null
>>> +++ b/drivers/devfreq/exynos-busfreq.c
>> 
>> []
>> 
>>> +
>>> +#define BUS_SATURATION_RATIO	40
>> 
>> In order to be a common driver, this should be tunable.
>> 
>> Because .dts is supposed to have hardware configuration only,
>> you may keep a table of { chip-name, saturation ratio} in this
>> driver and look up the saturation ratio based on the chip-name.
>
>OK, I'll add new property for saturation_ratio.
>
>I'll implement to use default saturation_ratio value ,
>if dt node don't include saturation_ratio property.

Yes. I didn't talk with DT maintainers and I do not have much
experience with DT; however, it appears that such values are not
recommended to be in DTS files and this value is determined by
the SoC model number without complications in the driver file.