On Fri, Jul 07, 2017 at 03:03:06PM +0200, Rafael J. Wysocki wrote: > On Friday, July 07, 2017 04:01:07 PM Peter Chen wrote: > > On Fri, Jul 07, 2017 at 03:13:48AM +0200, Rafael J. Wysocki wrote: > > > > > > > > - Can I write new code for it or I need to depend on something? > > > > > > There is nothing this code needs to depend on AFAICS, but there are > > > existing > > > solutions in this problem space (ACPI power management, genpd), so it > > > needs to > > > be careful enough about possible overlaps etc. > > > > > > > I find there is already "power state" concept at documentation. > > > > Documentation/ABI/testing/sysfs-devices-power_state > > > > > > This is ACPI-specific and only in sysfs directories representing ACPI > > > device > > > objects (which aren't physical devices). > > > > > > Anyway, since ACPI covers the problem space you are working in already, > > > your code has to be mutually exclusive with it. > > > > > > > - If I can write the new code for it, except the problems I want > > > > to fix, are there any other use cases I need to consider? > > > > > > I would start simple and focus on the particular problem at hand, that is > > > devices with two power states ("on" and "off") where the "on" state > > > depends on a number of clocks and/or GPIOs. Still, I'd also avoid making > > > design choices that might prevent it from being extended in the future > > > if need be. > > > > > > One major problem I can see is how to "attach" the power states framework > > > to a particular device (once we have discovered that it should be used > > > with > > > that device). > > > > > > For bus types that don't do power management of their own you could follow > > > ACPI (and genpd) and provide a PM domain for this purpose, but bus types > > > doing their own PM (like USB) will probably need to be treated > > > differently. > > > In those cases the bus type code will have to know that it should call > > > some > > > helpers to switch power states of devices. > > > > > > > After thinking more, using a power state framework is seems too heavy > > for this use case. This use case is just do some clock and gpio > > operations before device is created, and do some put operations > > after device is deleted. We just need some helpers in one structure > > (called "power sequence" or "power state") for this purpose. > > > > For the use case, the clock and gpio operation can be done after device > > is created, the power domain is more suitable. > > There is a problem with PM domains that they only provide hooks for runtime PM > and system suspend/resume (including hibernation) and not for generic > "power up" and "power down" operations that may need to be carried out at > probe time before the runtime PM framework can be used (and analogously > at remove time). > > I would consider starting with the patch below or similar. > > Then you can define something like POWER_STATE_SEQUENCE type for your > case and basically use almost what you have already with it, except that > struct pwrsec_generic will now become struct power_state_sequence and > struct power_state_info will be embedded in it instead of struct pwrsec. > > The major comceptual difference is that ->power_up and ->power_down are > now available at the level of the device that needs the power sequence and > pm_device_power_up/down() can be used wherever necessary (in the code, > in a bus type, in a controller driver or even in the driver for this > particular > device).
Rafeal, thanks for your patch. The biggest problem for my use case is the device is still not created. How can I call pm_device_power_up(dev)? Peter > > Most likely you will need a PM domain in addition to that, but mostly to avoid > code duplication. > > And in the future other types of power state definitions may be hooked up > to that, including ACPI etc. > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > --- > drivers/base/power/common.c | 35 +++++++++++++++++++++++++++++++++++ > include/linux/pm.h | 33 +++++++++++++++++++++++++++++++++ > 2 files changed, 68 insertions(+) > > Index: linux-pm/include/linux/pm.h > =================================================================== > --- linux-pm.orig/include/linux/pm.h > +++ linux-pm/include/linux/pm.h > @@ -550,6 +550,30 @@ struct pm_subsys_data { > #endif > }; > > +enum power_state_type { > + POWER_STATE_GENERIC = 0, > +}; > + > +/** > + * struct power_state_info - information related to device power states. > + * > + * @type: Power states definition type. > + * @power_up: Device power up method. > + * @power_down: Device power down method. > + * > + * @power_up is expected to put the device into a power state in which it can > + * be operated by software (it doesn't have to be the full power state in > + * principle as long as the device will respond to all software accesses in > + * this state) and @power_down is expected to put the device into the lowest > + * power state the device can be put into given all of the applicable > + * constraints and limitations (it may not mean completely off). > + */ > +struct power_state_info { > + enum power_state_type type; > + int (*power_up)(struct device *dev); > + int (*power_down)(struct device *dev); > +}; > + > struct dev_pm_info { > pm_message_t power_state; > unsigned int can_wakeup:1; > @@ -600,6 +624,7 @@ struct dev_pm_info { > unsigned long active_jiffies; > unsigned long suspended_jiffies; > unsigned long accounting_timestamp; > + struct power_state_info *state; > #endif > struct pm_subsys_data *subsys_data; /* Owned by the subsystem. */ > void (*set_latency_tolerance)(struct device *, s32); > @@ -610,6 +635,14 @@ extern void update_pm_runtime_accounting > extern int dev_pm_get_subsys_data(struct device *dev); > extern void dev_pm_put_subsys_data(struct device *dev); > > +#ifdef CONFIG_PM > +extern int pm_device_power_up(struct device *dev); > +extern int pm_device_power_down(struct device *dev); > +#else > +static inline int pm_device_power_up(struct device *dev) { return 0; } > +static inline int pm_device_power_down(struct device *dev) { return 0; } > +#endif /* CONFIG_PM */ > + > /** > * struct dev_pm_domain - power management domain representation. > * > Index: linux-pm/drivers/base/power/common.c > =================================================================== > --- linux-pm.orig/drivers/base/power/common.c > +++ linux-pm/drivers/base/power/common.c > @@ -152,3 +152,38 @@ void dev_pm_domain_set(struct device *de > device_pm_check_callbacks(dev); > } > EXPORT_SYMBOL_GPL(dev_pm_domain_set); > + > +/** > + * pm_device_power_up - Power up a device using the power states framework. > + * @dev: Device to power up. > + * > + * Put the device into a power state in which it will respond to all software > + * accesses (that may not mean maximum power) using the callback provided > + * through the device power state framework, if present. > + */ > +int pm_device_power_up(struct device *dev) > +{ > + if (dev->power.state && dev->power.state->power_up) > + return dev->power.state->power_up(dev); > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(pm_device_power_up); > + > +/** > + * pm_device_power_down - Power down a device using the power states > framework. > + * @dev: Device to power down. > + * > + * Put the device into the lowest power state it can be put into given the > + * applicable constraints and limitations (that may not mean maximum power) > + * using the callback provided through the device power state framework, if > + * present. > + */ > +int pm_device_power_down(struct device *dev) > +{ > + if (dev->power.state && dev->power.state->power_down) > + return dev->power.state->power_down(dev); > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(pm_device_power_down); > -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html