-been disabled during previous suspend calls and restoring all state that was
-saved in previous save_state calls.
+been disabled during previous suspend calls, such as IRQs and bus mastering,
+as well as calling pci_restore_state().
+
+If the device is currently in D3, it may need to be reinitialized in resume().
+
+ * Some types of devices, like bus controllers, will preserve context in D3hot
+ (using Vcc power). Their drivers will often want to avoid re-initializing
+ them after re-entering D0 (perhaps to avoid resetting downstream devices).
+
+ * Other kinds of devices in D3hot will discard device context as part of a
+ soft reset when re-entering the D0 state.
+
+ * Devices resuming from D3cold always go through a power-on reset. Some
+ device context can also be preserved using Vaux power.
+
+ * Some systems hide D3cold resume paths from drivers. For example, on PCs
+ the resume path for suspend-to-disk often runs BIOS powerup code, which
+ will sometimes re-initialize the device.