[PATCH v2 18/20] mmc: sdio: enable a default power off mode of the card

[Ohad Ben-Cohen]

On Thu, Jul 22, 2010 at 2:35 PM, Roger Quadros <roger.quadros at nokia.com> wrote:
> On 07/21/2010 08:33 PM, ext Ohad Ben-Cohen wrote:
>>
>> Add support for an SDIO device to stay powered off even without
>> the presence of an SDIO function driver. A host should explicitly
>> ask for it by means of MMC_CAP_DONT_POWER_CARD, and the SDIO
>> function driver should know it needs to call sdio_claim_power
>> before accessing the device.
>>
>> Signed-off-by: Ohad Ben-Cohen<ohad at wizery.com>
>
> Shouldn't this be the default behaviour? If there is no function driver for
> any of the functions of the card, then sdio core shold power off the card.
>
> I don't see a need for a special capability flag for this.
>
> in fact MMC_CAP_DONT_POWER_CARD does not seem like an mmc host's capability

Totally agree.

I didn't want to change the current behavior of the cards/funcs so I
looked for a way to explicitly power down only specific cards.

Alternatively we could power down all cards at the end
mmc_attach_sdio, and then power them up selectively in sdio_bus_probe,
just before calling probe. If the probe succeeds, the function driver
takes over. If the probe fails, we can power them down again.

Is that what you meant ?

This would work both if the sdio function driver is already loaded, or
will only be loaded at a later time. But I'm not too fond of the extra
power on/off cycles that it will introduce for each card..

Thanks,
Ohad.

> flag, it seems more like a request from the board to keep the card powered
> off.
>
> regards,
> -roger
>