[PATCH] mmc: mmci: Improve runtime PM support

[Russell King - ARM Linux]

On Mon, Oct 24, 2011 at 11:54:00AM +0200, Linus Walleij wrote:
> On Mon, Oct 24, 2011 at 11:36 AM, Russell King - ARM Linux
> <linux at arm.linux.org.uk> wrote:
> > On Sun, Oct 23, 2011 at 02:31:39AM +0200, Sebastian Rasmussen wrote:
> >> I guess the patch would appeal more to Russell if mmci_runtime_suspend()
> >> only cleared MCIMask0/SDI_MASK0 and MCIClock/SDI_CLKCR and left
> >> MCIPower/SDI_PWR unchanged. It may be the case that the signal direction
> >> bits need to be cleared for the ST-Ericsson PL180, but I haven't yet verified
> >> this on my Snowball dev board yet.
> >
> > There's also the issue that the specs call for the clock to run after
> > a command has completed for a certain number of cycles, and that the
> > clock must continue to run until the card reports not-busy after a
> > programming or erase cycle has completed - that can be long after the
> > previous command has 'completed'.
> 
> It's 8 cycles on MCLK required.

_Plus_ keeping the clock running while the card is signalling busy.

If you don't clock the card while its signalling busy, it will never
go non-busy (the data line becomes frozen.)