slim:msm: Add runtime PM to MSM slimbus controller
Runtime PM is used to turn clocks on and off when the controller is
not in use. There are 2 use-cases for the controller:
When the controller is used for messaging, pm_runtime_get is called
before sending the message. pm_runtime_put is called when message is
sent and/or response is received.
When the controller is used for data channels, pm_runtime_get is
called when data channel slot usage goes from 0 to non-zero.
pm_runtime_put can't be just called when data channel is scheduled
since data channel activity is going on until the data channel is
explicitly taken down. In that case, pm_runtime_put is called when
data channels are no longer using any slots on the bus.
pm_runtime_autosuspend is used to ensure that runtime_suspend doesn't
happen right after runtime enters idle state. This serves 2 purposes:
1. Resources aren't turned on/off too frequently.
2. There is a use case from audio where it does read/write to some
registers and the following data-channel setup happens from the LPASS
(satellite side). The timer ensures that there is no runtime_suspend
between these 2 activities.
Change-Id: I282e779380ae76058198e63c088aabfa3f1686fd
CRs-Fixed: 318901
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>
3 files changed