On 07/18/2013 01:36 AM, Tony Lindgren wrote: > * Stephen Warren <swarren@xxxxxxxxxxxxx> [130717 14:30]: >> On 07/16/2013 03:05 AM, Tony Lindgren wrote: ... >> Why shouldn't e.g. a pinctrl-based I2C mux also be able to do runtime >> PM? Does the mux setting select which states are used for runtime PM, or >> does runtime PM override the basic mux setting, or must the pincrl-I2C >> mux manually implement custom runtime-PM/pinctrl interaction since >> there's no generic answer to those questions? How many more custom >> exceptions will there be? > > The idea is that runtime PM will never touch the basic mux settings > at all. The "default" state should be considered a static state > that is claimed during driver probe, and released when the driver > is unloaded. This is typically let's say 90% of the pins for any > device. > > For runtime PM, we can just toggle the PM related pinctrl states as > they have been verified to match the active state during init. > > So I don't see why pinctrl-I2C would have to do anything specific. > All that is required is that the pins are grouped for the consumer > driver, and we can provide some automated checks on the states for > runtime PM. So, consider a pinctrl-based I2C mux. It has 2 states to cover two I2C buses: a) bus 1: I2C controller is muxed out onto one set of pins. b) bus 2: I2C controller is muxed out onto another set of pins. Now, the system could go idle in either of those 2 states, and then later need to return to one of those states. I just don't see how that would work, since the runtime PM code in this series switches to *an* active state when the device becomes non-idle. If the definition of the idle state switches the mux function for both sets of pins to some idle/quiescent value, then you'd need to do different reprogramming when going back to "the" active state; I guess the system would need to remember which state was active before switching to idle, then switch back to that same state rather than hard-coding the active state name as "active"... -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
