diff options
Diffstat (limited to 'include/linux/pm.h')
| -rw-r--r-- | include/linux/pm.h | 62 |
1 files changed, 47 insertions, 15 deletions
diff --git a/include/linux/pm.h b/include/linux/pm.h index 096fb6f754cf..6b27e07aef19 100644 --- a/include/linux/pm.h +++ b/include/linux/pm.h @@ -142,29 +142,61 @@ typedef struct pm_message { } pm_message_t; /* - * There are 4 important states driver can be in: - * ON -- driver is working - * FREEZE -- stop operations and apply whatever policy is applicable to a - * suspended driver of that class, freeze queues for block like IDE - * does, drop packets for ethernet, etc... stop DMA engine too etc... - * so a consistent image can be saved; but do not power any hardware - * down. - * SUSPEND - like FREEZE, but hardware is doing as much powersaving as - * possible. Roughly pci D3. + * Several driver power state transitions are externally visible, affecting + * the state of pending I/O queues and (for drivers that touch hardware) + * interrupts, wakeups, DMA, and other hardware state. There may also be + * internal transitions to various low power modes, which are transparent + * to the rest of the driver stack (such as a driver that's ON gating off + * clocks which are not in active use). * - * Unfortunately, current drivers only recognize numeric values 0 (ON) and 3 - * (SUSPEND). We'll need to fix the drivers. So yes, putting 3 to all different - * defines is intentional, and will go away as soon as drivers are fixed. Also - * note that typedef is neccessary, we'll probably want to switch to - * typedef struct pm_message_t { int event; int flags; } pm_message_t - * or something similar soon. + * One transition is triggered by resume(), after a suspend() call; the + * message is implicit: + * + * ON Driver starts working again, responding to hardware events + * and software requests. The hardware may have gone through + * a power-off reset, or it may have maintained state from the + * previous suspend() which the driver will rely on while + * resuming. On most platforms, there are no restrictions on + * availability of resources like clocks during resume(). + * + * Other transitions are triggered by messages sent using suspend(). All + * these transitions quiesce the driver, so that I/O queues are inactive. + * That commonly entails turning off IRQs and DMA; there may be rules + * about how to quiesce that are specific to the bus or the device's type. + * (For example, network drivers mark the link state.) Other details may + * differ according to the message: + * + * SUSPEND Quiesce, enter a low power device state appropriate for + * the upcoming system state (such as PCI_D3hot), and enable + * wakeup events as appropriate. + * + * FREEZE Quiesce operations so that a consistent image can be saved; + * but do NOT otherwise enter a low power device state, and do + * NOT emit system wakeup events. + * + * PRETHAW Quiesce as if for FREEZE; additionally, prepare for restoring + * the system from a snapshot taken after an earlier FREEZE. + * Some drivers will need to reset their hardware state instead + * of preserving it, to ensure that it's never mistaken for the + * state which that earlier snapshot had set up. + * + * A minimally power-aware driver treats all messages as SUSPEND, fully + * reinitializes its device during resume() -- whether or not it was reset + * during the suspend/resume cycle -- and can't issue wakeup events. + * + * More power-aware drivers may also use low power states at runtime as + * well as during system sleep states like PM_SUSPEND_STANDBY. They may + * be able to use wakeup events to exit from runtime low-power states, + * or from system low-power states such as standby or suspend-to-RAM. */ #define PM_EVENT_ON 0 #define PM_EVENT_FREEZE 1 #define PM_EVENT_SUSPEND 2 +#define PM_EVENT_PRETHAW 3 #define PMSG_FREEZE ((struct pm_message){ .event = PM_EVENT_FREEZE, }) +#define PMSG_PRETHAW ((struct pm_message){ .event = PM_EVENT_PRETHAW, }) #define PMSG_SUSPEND ((struct pm_message){ .event = PM_EVENT_SUSPEND, }) #define PMSG_ON ((struct pm_message){ .event = PM_EVENT_ON, }) |