Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes: > On Mon, 31 Jan 2011, Rajendra Nayak wrote: > >> Can you elaborate a bit more on how/why runtime PM transitions >> are disabled during system suspend, and how is it taken care >> of that a runtime resume of a device works however a subsequent >> runtime (re)suspend does not? > > I'll answer for Kevin. This is done by the PM core, in order to > prevent runtime power transitions from interfering with a system power > transition. The PM core increments the device's usage_count; this > prevents the device from being runtime-suspended but it allows > runtime-resume calls to go through. I understand how this works, but frankly I'm still a bit fuzzy on why. I guess I'm still missing a good understanding of what "interfering with a system power transition" means, and why a runtime suspend qualifies as interfering but not a runtime resume. More specifically, the reason for $SUBJECT patch is precisely because a runtime resume is allowed, a runtime suspend is not, and thus a system power transititon is prevented. Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
