Re: [PATCH] [RFC] mmc: perform SDIO reset on power restore of host

[Arnd Hannemann <arnd@arndnet.de>]

Hi Ohad,

Am 28.12.2010 15:24, schrieb Ohad Ben-Cohen:
>>> Do you mean that your card is always powered on regardless of
>>> mmc_power_off() invocations ?
>>
>> Yes, it seems so.
> 
> Ok, thanks for letting us know.
> 
> It bothered me that we didn't understand the issue you had, but now it
> seems that MMC_CAP_POWER_OFF_CARD is the right solution for you as
> well.
> 
>> Even if the card is kept powered, when mmc_power_off() is called, the
>> host controller will stop the SD bus clock. So I believe at least some
>> power is saved this way and MMC_CAP_POWER_OFF_CARD makes sense?
> 
> Well, with some SDIO cards, the host controller can use the recently
> added aggressive clock gating framework to stop the clock on
> inactivity, and not wait until the card is powered off.
> 
> Currently that clock gating framework is still disabled for SDIO
> cards, but this is just temporary until we sort out how to use it
> safely for SDIO as well.

So you suggest to don't set MMC_CAP_POWER_OFF_CARD for the boards which
keep the card powered, but instead wait for the clock gating framework?
 
> For example, the wl1271 card has asynchronous interrupts (via external
> irq) so we can safely stop its clock on inactivity.
> 
> Do you know if that's possible with your card as well ?

I don't think so, the card is a normal SDIO card which plugs into a normal
MMC/SD slot, no extra pins or such. However SDIO IRQs are available, but you
don't mean that, do you?

Thanks,
Arnd