Date:	Tue, 7 Aug 2012 13:38:53 +0900
From:	Kyungmin Park <kmpark@...radead.org>
To:	Thomas Abraham <thomas.abraham@...aro.org>
Cc:	Olof Johansson <olof@...om.net>,
	Dongjin Kim <Dongjin.Kim@...eeyamobility.net>,
	Dongjin Kim <tobetter@...il.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Tony Lindgren <tony@...mide.com>,
	Jon Medhurst <tixy@...t.co.uk>,
	Shawn Guo <shawn.guo@...aro.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: ȸ½Å: ȸ½Å: [PATCH] ODROID-X: hkdk4412: Add new hardware based on Exynos4412

On 8/7/12, Thomas Abraham <thomas.abraham@...aro.org> wrote:
> On 7 August 2012 07:58, Olof Johansson <olof@...om.net> wrote:
>> Hi,
>>
>> On Mon, Aug 6, 2012 at 7:05 PM, Dongjin Kim
>> <Dongjin.Kim@...eeyamobility.net> wrote:
>>> Hello,
>>>
>>> I am trying to understand what I have to do for device tree.
>>>
>>> In order to create dts file for ODROID-X hardware, it seems I may need
>>> dts file of EXYNOS4412 SoC.
>>> But maybe exynos4412.dtsi is not merged yet or not exist, like
>>> exynos4210.dtsi or exynos5250.dtsi.
>>> Obviously it seems not easy to create such a file without SoC datasheet,
>>> and I do not have it.
>>>
>>> So do I wait for the file to be merged by Samsung or better to create
>>> initial dts file cloned from exynos4210.dtsi and modify to have verified
>>> nodes with the source/header files?
>>
>> Ideally they already have one waiting to be submitted, but that might
>> not be the case. Given that the origenboard design with 4412 is not
>> yet shipping, I'm guessing the Linaro Samsung engineers might not have
>> done much work on 4412 yet. Kukjin? Thomas?
>>
>>> What's your suggestion?
>>
>> The alternative is to use the data you have available -- i.e. sources
>> and patches, and craft the device tree from there. The design of 4412
>> is a derivative from 4210, so that's a good start. Next step would be
>> to describe the board on top of the SoC, peripherals, etc. Take a look
>> at how the origen board support was added, and so on.
>>
>> I ordered an odroid-x several weeks ago but I haven't have a confirmed
>> shipping date yet. :( I'm not sure how long it'll be before I can help
>> out, unfortunately.
>>
>>
>> -Olof
>
> Most of the Exynos4210 device tree support can be reused for
> Exynos4412 as well. Looking at the hardware differences between the
> two, it might be better to create a new exynos4.dtsi file (kind of
> creating it out of the existing exynos4210.dtsi) which will have all
> the common bits across all SoC's in the Exynos4 family.
>
> Further, there can be exynos4210.dtsi and exynos4412.dtsi which would
> specify SoC specific differences such as the GIC cpu-offset property
> and the additional groups available in the interrupt combiner.
>
> There are differences in the gpio/pinmux controllers as well which
> have to be described using device tree. The current gpio/pinmux device
> tree support depends entirely on the gpio-samsung driver which handles
> both gpio and pinmux but requires listing all the banks available in
> Exynos4412. I would prefer not to do that since we are switching over
> to using a pin controller driver and I am currently working on this
> driver.
>
> The pin controller driver is important without which the
> gpio/pinmux/pinconf setting for devices such as i2c and sdhci
> controller cannot be setup. The basic pinctrl driver for Exynos4 has
> already been posted and now I am working on adding gpio and wakeup
> interrupt support into that driver (hoping to complete it this week).
>
> So the probable steps in getting started with using device tree for
> Exynos4412 would be
>
> 1. Create a new exynos4.dtsi file with all the Exynos4 common
> properties for all dt supported controllers.
> 2. Update the exynos4210.dtsi file accordingly and add the new
> exynos4412.dtsi file.
> 3. With this, it will be possible to boot the kernel and test
> peripherals that do not depend on gpio/pinmux (rtc, wdt, etc).
> 4. When the Exynos4 pinctrl driver is available, start adding device
> nodes for i2c and sdhci controllers.
> 5. Incrementally add device tree coverage for the board and other
> peripherals on Exynos4412.
Nice!
Good plan as I thnk.

Thank you,
Kyungmin Park
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