[PATCH 11/15] wireless: wl1271: introduce platform device support

[Nicolas Pitre]

On Wed, 7 Jul 2010, Roger Quadros wrote:

> On 07/06/2010 08:42 PM, ext Nicolas Pitre wrote:
> > On Tue, 6 Jul 2010, Roger Quadros wrote:
> > 
> > > OK, this is how I see it.
> > > 
> > > - Treat the non-removable card as non-removable. So no need to do card
> > > detect
> > > emulation.
> > > 
> > > - Treat the GPIO power enable on wl1271 as VMMC supply. Use fixed
> > > regulator
> > > framework to define this regulator&  supply. Even though you mention that
> > > it
> > > is not actually a supply, it fits well in the fixed supply framework.
> > > 
> > > - When the host controller is enumerated, the mmc core will power up the
> > > slot,
> > > find the sdio card, and probe the function driver (i.e. wl1271_sdio).
> > > 
> > > - if interface is not in use, the function driver must release the sdio
> > > host,
> > > and this should eventually disable the vmmc supply.
> > > 
> > > - Whenever the wlan interface must be brought up, wl1271_sdio, can claim
> > > the
> > > sdio host. this will cause the vmmc supply to be enabled, for as long as
> > > the
> > > interface is up.
> > > 
> > > Does this address all issues?
> > 
> > This is mostly all good, except that claiming/releasing the SDIO host is
> > about access to the bus.  It must be claimed right before doing any IO,
> > and released right after that, even when the card is expected to remain
> > powered.  This is not the proper place to hook power control.
> 
> Agreed, but is it so that SDIO power may be removed between a host_release and
> claim? This appears so from omap_hsmmc host controller.

No, it is not because a host is not claimed that power should be 
dropped.  The host claim/release is meant to provide exclusive access to 
the card that's all.

If the OMAP controller is dropping power to the card upon 
host->disable() then it is wrong.  AFAICS only the OMAP controller is 
playing such games at the moment and I suspect the semantics might not 
be all right.  Shutting down the _controller_ when it is idle might be a 
good thing, but not power to the _card_.  Only the function driver might 
know when it is fine to lose power.


Nicolas