Messages in this thread | | | Date | Tue, 26 Apr 2005 02:23:14 -0400 | From | Adam Belay <> | Subject | Re: [PATCH] PCI: Add pci shutdown ability |
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On Tue, Apr 26, 2005 at 02:32:29PM +1000, Benjamin Herrenschmidt wrote:
-->snip
> > I don't like this notion of "stop" separated from power states anyway, I > think it just doesn't work in practice.
Yeah, after giving it some additional thought, I think there are better ways.
> > Ben. >
Ok, here's a new idea.
For many devices "->suspend" and "->resume" with pm_message_t is exactly what we need. However, as we support more advanced power management features, such as runtime power management, or power containers, we need something a little more specific. The exact power state must be specified among other issues.
We might do something like this:
Keep "->suspend" and "->resume" around unchanged. (so the states would probably remain as PMSG_FREEZE and PMSG_SUSPEND). If the driver doesn't support the more advanced PM methods just use these. They work well enough for system sleep states etc.
Alternatively drivers could support a more rich power management interface via the following methods:
change_state - changes a device's power state
change_state(struct device * dev, pm_state_t state, struct system_state * sys_state, int reason); @dev - the device @state - the target device-specific power state @sys_state - a data structure containing information about the intended global system power state @reason - why the state must be changed (ex. RUNTIME_PM, SYSTEM_SLEEP, SYSTEM_RESUME, etc.)
halt - acts somewhat like PMSG_FREEZE, stops device activity, doesn't change power state
halt(struct device * dev, struct system_state * sys_state, int reason); @dev - the device @sys_state - a data structure containing information about the intended global system power state @reason - why we are halting operation (ex. RUNTIME_CHANGES (like cpufreq), SYSTEM_SLEEP, SHUTDOWN, REBOOT)
contine - resumes from a "halt"
continue(struct device * dev, struct system_state * sys_state, int reason); @dev - the device @sys_state - a data structure containing information about the intended global system power state @reason - why we are resuming operation (ex. RUNTIME_CHANGES (like cpufreq), SYSTEM_RESUME)
When changing system state, we call "change_state" for every device with power resources. Devices that do not directly consume power or have power states will not implement "change_state" so we will call "halt" and "continue" instead.
When shutting down the system, halt has the option of turning off the device, as it will see the SHUTDOWN reason. So it's a driver-knows-best approach instead of assuming everything must be turned off, or everything must just be stopped.
So in theory, with cpufreq, we could stop userspace, ->halt every device (drivers won't do anything if they know it's not necessary), change the frequency, and then resume operation.
We may want to create structures like pm_message_t for "change_state", "halt", and "continue". Pavel, do you have any thoughts on this?
This is just a rough idea... I look forward to any comments or suggestions.
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