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

[Roger Quadros <roger.quadros@nokia.com>]

On 07/06/2010 08:42 PM, ext Nicolas Pitre wrote:
> On Tue, 6 Jul 2010, Roger Quadros wrote:
>
>> On 07/06/2010 03:53 PM, ext Ohad Ben-Cohen wrote:
>>> Hi Roger,
>>>
>>> On Tue, Jul 6, 2010 at 1:35 PM, Roger Quadros<roger.quadros@nokia.com>
>>> wrote:
>>>> My point is that shouldn't this be handled by SDIO core?
>>>
>>> Care to explain what you mean / give a code example ?
>>
>> If the Power enable GPIO can be treated as SDIO slot supply (i.e. vmmc), then
>> the SDIO/MMC core should tackle it, just like it deals with supply for slots
>> with removable cards.
>
> Exact.
>
>>> You need card detect events in order to trigger card&   sdio function
>>> initialization and removals.
>
> Why would you trigger function initialization and removal?  Just to turn
> off power?  That's a bit like pulling off the battery from your laptop
> when you want to suspend it.  There is a better way to go about things.
>
>>> Please share any alternative approach you may be thinking on.
>>
>> 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.

if we have sdio_claim_power() and sdio_release_power() in place then power 
control should depend on it.

regards,
-roger