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

[Ulf Hansson]

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