[linux-sunxi] [PATCH v2 1/4] dt: bindings: mmc: Document the practice of using subnodes for slots

[Jaehoon Chung]

+ Seungwon Jeon

On 06/02/2014 05:52 PM, Ulf Hansson wrote:
> On 2 June 2014 10:46, Jaehoon Chung <jh80.chung at samsung.com> wrote:
>> On 06/02/2014 05:38 PM, Jaehoon Chung wrote:
>>> On 06/02/2014 05:29 PM, Ulf Hansson wrote:
>>>> On 1 June 2014 11:23, Hans de Goede <hdegoede at redhat.com> wrote:
>>>>> Hi,
>>>>>
>>>>>
>>>>> On 05/31/2014 10:13 PM, Olof Johansson wrote:
>>>>>>
>>>>>> On Sat, May 31, 2014 at 12:03 PM, Hans de Goede <hdegoede at redhat.com>
>>>>>> wrote:
>>>>>>>
>>>>>>> The following existing MMC host controller bindings use slot subnodes:
>>>>>>>
>>>>>>> Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt
>>>>>>> Documentation/devicetree/bindings/mmc/k3-dw-mshc.txt
>>>>>>> Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
>>>>>>> Documentation/devicetree/bindings/mmc/socfpga-dw-mshc.txt
>>>>>>> Documentation/devicetree/bindings/mmc/atmel-hsmci.txt
>>>>>>> Documentation/devicetree/bindings/mmc/rockchip-dw-mshc.txt
>>>>>>>
>>>>>>> This commit documents this practice in the standard mmc bindings
>>>>>>> documentation.
>>>>>>>
>>>>>>> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
>>>>>>
>>>>>>
>>>>>> There are today only two drivers that use this kind of binding, dw_mmc
>>>>>> and the at91 one.
>>>>>
>>>>>
>>>>> Correct.
>>>>>
>>>>>
>>>>>> Neither seems to actually ever have been used with
>>>>>> more than one slot. I doubt anyone building an exynos-based system
>>>>>> will ever do a multi-slot solution, and it seems that the at91 driver
>>>>>> doesn't actually handle more than one slot.
>>>>>>
>>>>>> I'm personally not that excited about complicating the bindings by
>>>>>> opening up for this -- I would rather work towards removing the
>>>>>> concept of slots if it's one of those things that are going to remain
>>>>>> unused. We have actually been talking about reworking the dw_mmc
>>>>>> binding to remove the slot concept (and simplify the driver by doing
>>>>>> so).
>>>>>
>>>>>
>>>>> I'm fine with removing the slot subnode, I added it because of it being
>>>>> brought up in the powerup sequence discussion. I explicitly asked there
>>>>> if adding such a subnode level was seen as desirable but nobody
>>>>> answered :|
>>>>>
>>>>> Anyways, either way works for me. I can do a v3 dropping the slot subnode
>>>>> level again. I would really like to move forward with a decision on how-to
>>>>> represent non probable info for sdio devices in device nodes. So do you
>>>>> have any other remarks other then that the slot subnode should be dropped ?
>>>>> And if not can you please review and ack (*) v3 of this patch-set once
>>>>> I've send it?
>>>>>
>>>>> Chris Ball and Ulf Hansson, what is your take on this, are you willing to
>>>>> take this patch set? And do you want it with or without the slot subnodes ?
>>>>
>>>> I certainly appreciate you working actively on this Hans, I will look
>>>> into the patchset as soon as I can.
>>>>
>>>> I share Olof's view about the slot nodes, we must not add DT bindings
>>>> that isn't really needed.
>>>>
>>>> Regarding the slot subnodes; Jaehoon Chung recently posted a patchset
>>>> for adding the parsing of it, intended for dwmmc. I withdraw my ack
>>>> for it, and let's try to go in the other direction instead.
>>>>
>>>> [PATCHv3 0/4] mmc: fixed the mmc_of_parse for dwmmc.
>>>>
>>>> Thus I suggest we should clean-up host drivers to support only one
>>>> card per host, and entirely skip the slot concept.
>>>
>>> Well, almost platform is used the only one card per host, although some controller is supported the slot concept.
>>> But we don't know that controller should be used the multi slot per host, in future.
>>> So I think we can't skip the slot concept.
>> If we need to change the dw-mmc controller, let me know, plz.
>> I want to fix this problem before release the 3.16.
>> Actually, i think it can remove the subnode, if ensure not to use multi-slot at dwmmc.
> 
> That seems like the best approach. Please try to remove the subnodes
> and make use of mmc_of_parse, as is.
> 
> Kind regards
> Uffe
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