Re: [PATCH] mmc: mmci: Improve runtime PM support
Russell King - ARM Linux wrote:
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@xxxxxxxxxxxxxxxx> 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.)
Good point!Is the aggressive clk gating feature in the mmc framework taking this into account as well?
Potentially the framework could do a get_sync/put (in claim/release host) to prevent hosts from being runtime disabled. Similar how the enable/disable mechanism is working.
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