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

[Ulf Hansson]

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.

Kind regards
Uffe

>
> Thanks & Regards,
>
> Hans
>
>
> *) Assuming you don't find any issues