| # Device power management |
| |
| Caution: This page may contain information that is specific to the legacy |
| version of the driver framework (DFv1). |
| |
| The [zx_device_ops_t][device] *suspend* hook is sequenced before itself (e.g. |
| if a request to suspend to D1 happens, and while that is being executed a |
| request to suspend to D2 happens, the first will finish before the latter |
| begins). It is also sequenced before the *resume* hook. |
| |
| The `set_performance_state` hook is sequenced before itself. |
| It has no particular ordering with suspend/resume hooks. |
| After the driver returns from the set_performance_state hook with success, |
| it is assumed by power manager that the device is operating at the requested |
| performance state whenever the device is in working state. Since the hook only |
| executes on the driver host's main thread, multiple requests are not executed |
| concurrently. |
| On success, the out_state and the requested_state is same. If the device is in a |
| working state, the performance state will be changed to requested_state immediately. |
| If the device is in non-working state, the performance state will be the requested_state |
| whenever the device transitions to working state. |
| On failure, the out_state will have the state that the device can go into. |
| |
| The `configure_autosuspend` hook is sequenced before itself and is used to configure whether |
| devices can suspend or resume themselves depending on their idleness. The hook is called with |
| the deepest sleep state the device is expected to be in which is when the device is suspended. |
| If the entire system is being suspended to a sleep state, the driver should expect `suspend` |
| hook to be called, even if the auto suspend is configured. It is not supported to selectively |
| suspend a device when auto suspend is configured. |
| |
| |
| [device]: /src/lib/ddk/include/lib/ddk/device.h |
