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

[Mark Brown]

On Wed, May 28, 2014 at 01:47:50PM +0200, Tomasz Figa wrote:

> Moreover, there are already WLAN chips available that can use HSIC as
> their host interface and I'm not talking here about some exotic
> products, but rather widely recognized products of Broadcom (BCM4335),
> Marvell (88W8797) or Qualcomm Atheros (AR6004).

> My conclusion is that I see the discussion here being too much focused
> on MMC, especially considering the fact that the whole problem doesn't
> have anything to do with MMC, which is just used as (one of possible)
> host interface.

Right, the other example I keep mentioning for this is Slimbus where
some sort of external power control is required to trigger enumeration
in normal operation for common use cases.

> IMHO, all we need here is a way to tell the MMC (or HSIC) core when to
> look for a new device and when not (e.g. power down the host controller
> completely). Anything else, including proper power sequencing is up to
> the platform driver of such non-discoverable device - it's only its host
> interface that is discoverable when enabled. I believe this simplistic
> approach would lead to much less new code added, better reusability of
> code (power sequencing independent of host interface) and no need to
> create overly generic code, which usually turns out to be not generic
> enough.

We then have the problem of working out where that platform driver comes
from, for many of these buses the device can be completely described as
just a device on the parent bus with some resources connected.
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