Subject: RFC: representing sdio devices oob interrupt, clks, etc. in device tree

From: [email-masked] (Hans de Goede)
Date: Sat, 24 May 2014 12:10:58 +0200

Hi,

On 05/23/2014 04:54 PM, Arend van Spriel wrote:
> On 05/23/14 15:28, Hans de Goede wrote:
>> Hi,
>>
>> On 05/23/2014 03:21 PM, Arend van Spriel wrote:
>>> On 05/23/14 13:50, Hans de Goede wrote:
>>>> Hi,
>>>>
>>>> On 05/23/2014 01:22 PM, Mark Brown wrote:
>>>>> On Fri, May 23, 2014 at 11:13:44AM +0200, Hans de Goede wrote:
>>>>>
>>>>>> Thinking more about this, I would like to make one change to my
>>>>>> proposal, the mmc-core should only do power up of child-nodes if
>>>>>> they have a compatible of: "simple-sdio-powerup". This way
>>>>>> when we add something more complex, we can keep the simple powerup
>>>>>> code in the mmc core, keeping what we've already using this working
>>>>>> and the mmc core won't respond to the child nodes for more complex
>>>>>> devices, so it won't conflict with more complex power-up handling
>>>>>> handled by some other driver.
>>>>>
>>>>> Would it not be better to have this be something in the driver struct
>>>>> rather than in the device tree?  Putting a compatible in there would be
>>>>> encoding details of the Linux implementation in the DT which doesn't
>>>>> seem right especially since these are details we're thinking of changing
>>>>> later on.
>>>>
>>>> The compatible is not a Linux specific thing, it is a marking saying
>>>> that something needs to take care of enabling the clks (and whatever
>>>> else we will make part of the binding for this compatible), before
>>>> scanning the mmc bus.
>>>>
>>>>> Something like have the driver set flags saying if it wants
>>>>> to do complicated things.
>>>>
>>>> Chicken<->   egg, we won't know which driver to use before we've probed
>>>> the mmc bus, and we cannot probe the bus before enabling the clks, etc.
>>>
>>> The approach I took with brcmfmac is that upon module init I search the DT for "brcm,bcm43xx-fmac" compatible and get the clock and/or gpio resource and enable them before registering the sdio driver. The difficulty is probably when using the driver built-in as the clocks and gpios may not be available yet and we can not rely on deferred probing in module init stage.
>>
>> I know, and that approach does not work, by the time the brcmfmac loads,
>> the mmc core has long probed the mmc bus and decided no one is home.
> 
> Ok. That is due to the non-removable property, right? I assumed a mmc rescan, which is (supposedly) triggered upon sdio driver registration, would subsequently find the device.

That is what I thought, but I tried without the non-removable property and
the sdio wifi was still not recognized.

Regards,

Hans