| Message ID | 20140227023455.GA15712@kahuna (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
Quoting Nishanth Menon (2014-02-26 18:34:55) > +/** > + * pm_runtime_get_rate() - Returns the device operational frequency > + * @dev: Device to handle > + * @rate: Returns rate in Hz. > + * > + * Returns appropriate error value in case of error conditions, else > + * returns 0 and rate is updated. The pm_domain logic does all the necessary > + * operation (which may consider magic hardware stuff) to provide the rate. > + * > + * NOTE: the rate returned is a snapshot and in many cases just a bypass > + * to clk api to set the rate. > + */ > +int pm_runtime_get_rate(struct device *dev, unsigned long *rate) Instead of "rate", how about we use "level" and leave it undefined as to what that means? It would be equally valid for level to represent a clock rate, or an opp from a table of opp's, or a p-state, or some value passed to a PM microcontroller. Code that is tightly coupled to the hardware would simply know what value to use with no extra sugar. Generic code would need to get the various supported "levels" populated at run time, but a DT binding could do that, or a query to the ACPI tables, or whatever. > +{ > + unsigned long flags; > + int error = -ENOSYS; > + > + if (!rate || !dev) > + return -EINVAL; > + > + spin_lock_irqsave(&dev->power.lock, flags); > + if (!pm_runtime_active(dev)) { > + error = -EINVAL; > + goto out; > + } > + > + if (dev->pm_domain && dev->pm_domain->active_ops.get_rate) > + error = dev->pm_domain->active_ops.get_rate(dev, rate); > +out: > + spin_unlock_irqrestore(&dev->power.lock, flags); > + > + return error; > +} > + > +/** > + * pm_runtime_set_rate() - Set a specific rate for the device operation > + * @dev: Device to handle > + * @rate: Rate to set in Hz > + * > + * Returns appropriate error value in case of error conditions, else > + * returns 0. The pm_domain logic does all the necessary operation (which > + * may include voltage scale operations or other magic hardware stuff) to > + * achieve the operation. It is guarenteed that the requested rate is achieved > + * on returning from this function if return value is 0. > + */ > +int pm_runtime_set_rate(struct device *dev, unsigned long rate) Additionally I wonder if the function signature should include a way to specify the sub-unit of a device that we are operating on? This is a way to tackle the issues you raised regarding multiple clocks per device, etc. Two approaches come to mind: int pm_runtime_set_rate(struct device *dev, int index, unsigned long rate); Where index is a sub-unit of struct device *dev. The second approach is to create a publicly declared structure representing the sub-unit. Some variations on that theme: int pm_runtime_set_rate(struct perf_domain *perfdm, unsigned long rate); or, int pm_runtime_set_rate(struct generic_power_domain *gpd, unsigned long rate); or whatever that sub-unit looks like. The gpd thing might be a total layering violation, I don't know. Or perhaps it's a decent idea but it shouldn't be as a PM runtime call. Again, I dunno. Regards, Mike -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 02/26/2014 11:00 PM, Mike Turquette wrote: > Quoting Nishanth Menon (2014-02-26 18:34:55) >> +/** >> + * pm_runtime_get_rate() - Returns the device operational frequency >> + * @dev: Device to handle >> + * @rate: Returns rate in Hz. >> + * >> + * Returns appropriate error value in case of error conditions, else >> + * returns 0 and rate is updated. The pm_domain logic does all the necessary >> + * operation (which may consider magic hardware stuff) to provide the rate. >> + * >> + * NOTE: the rate returned is a snapshot and in many cases just a bypass >> + * to clk api to set the rate. >> + */ >> +int pm_runtime_get_rate(struct device *dev, unsigned long *rate) > > Instead of "rate", how about we use "level" and leave it undefined as to > what that means? It would be equally valid for level to represent a > clock rate, or an opp from a table of opp's, or a p-state, or some value > passed to a PM microcontroller. IMHO, from a driver which already exists for multiple SoCs/ architectures, we cannot have variant definitions that a generic driver will be unable to depend upon. what should such a driver expect? level == rate OR level == index to p-state or magic PM controller value? Today the definitions are very clear to such a driver, pm_runtime APIs are used for device specific idle management, but for active management, use clk and regulator code as needed - ofcourse, that machine specificity triggers the need for the 50 odd cpufreq drivers we have today - intent was to be able to abstract it enough for a generic logic to exist. > > Code that is tightly coupled to the hardware would simply know what > value to use with no extra sugar. agreed on the machine specific implementation, but the logic at driver level will then get tied down to machine specific implementation as well > > Generic code would need to get the various supported "levels" populated > at run time, but a DT binding could do that, or a query to the ACPI > tables, or whatever. then we'd also have to introduce a translator API for drivers that need frequency -> we go back to the old world of having specific functions depending on usage in the frequency world, ACPI world, PM controller world. That completely breaks the concept of having a higher level function, right? > >> +{ >> + unsigned long flags; >> + int error = -ENOSYS; >> + >> + if (!rate || !dev) >> + return -EINVAL; >> + >> + spin_lock_irqsave(&dev->power.lock, flags); >> + if (!pm_runtime_active(dev)) { >> + error = -EINVAL; >> + goto out; >> + } >> + >> + if (dev->pm_domain && dev->pm_domain->active_ops.get_rate) >> + error = dev->pm_domain->active_ops.get_rate(dev, rate); >> +out: >> + spin_unlock_irqrestore(&dev->power.lock, flags); >> + >> + return error; >> +} >> + >> +/** >> + * pm_runtime_set_rate() - Set a specific rate for the device operation >> + * @dev: Device to handle >> + * @rate: Rate to set in Hz >> + * >> + * Returns appropriate error value in case of error conditions, else >> + * returns 0. The pm_domain logic does all the necessary operation (which >> + * may include voltage scale operations or other magic hardware stuff) to >> + * achieve the operation. It is guarenteed that the requested rate is achieved >> + * on returning from this function if return value is 0. >> + */ >> +int pm_runtime_set_rate(struct device *dev, unsigned long rate) > > Additionally I wonder if the function signature should include a way to > specify the sub-unit of a device that we are operating on? This is a way > to tackle the issues you raised regarding multiple clocks per device, > etc. Two approaches come to mind: > > int pm_runtime_set_rate(struct device *dev, int index, > unsigned long rate); > > Where index is a sub-unit of struct device *dev. Here the problem is trying to define what that index is. should it be clk index? how again would a generic driver be able to consistently function? lets, for a moment replace that with a string - "clk_name" to uniquely identify the clk -> but then, it still, in concept makes it no better than a clk_set_rate since we are uniquely identifying the clk to operate upon -> and we can definitely add "magic dvfs" stuff on existing clock framework without a need for additional wrappers (which what the original $subject series does). >The second approach is > to create a publicly declared structure representing the sub-unit. Some > variations on that theme: > > int pm_runtime_set_rate(struct perf_domain *perfdm, unsigned long rate); > > or, > > int pm_runtime_set_rate(struct generic_power_domain *gpd, > unsigned long rate); > > or whatever that sub-unit looks like. The gpd thing might be a total > layering violation, I don't know. Or perhaps it's a decent idea but it > shouldn't be as a PM runtime call. Again, I dunno. Again, we goes back to the same question, right? which clock in a power_domain/perf_domain are we intending with the rate? a device belongs to a perf domain -> Taking drivers/cpufreq/imx6q-cpufreq.c as an example. Clocks needed: arm_clk, pll1_sys_clk, pll1_sw_clk, step_clk, pll2_pfd2_396m_clk. regulators needed: arm_reg, pu_reg, soc_reg. The device we want to set a frequency is the ARM processor. by describing "perf_domain" or "generic power domain" as a single clock entity, we might as well use clk_set_rate instead to be specific, instead of writing one wrapper on top of the entire thing. I apologize, more I think in this angle, less I think such a generic api seems feasible.
Hi, On Wed, Feb 26, 2014 at 08:34:55PM -0600, Nishanth Menon wrote: > On 14:56-20140225, Nishanth Menon wrote: > > On 02/24/2014 11:51 PM, Mike Turquette wrote: > > > Quoting Nishanth Menon (2014-02-18 12:32:18) > [...] > > > I'm not sure about trying to capture the "voltdm" as a core concept. It > > > feels a bit unwieldy to me. > > > > Considering it is a simple collation of regulators and SoC specific > > "magic" which have to be operated in tandem to clock operation, Why > > does it seem unwieldy? Usage of multiple voltage planes in a single > > voltage domain concept does not seem unique to TI processors either: > > For example, imx6q-cpufreq.c uses 3 regulators (arm, pu, soc), > > s5pv210-cpufreq.c uses two regulators (vddarm, vddint), ideally OMAP > > implementation would use two (vdd_mpu, vbb_mpu). > > > > > I have wondered about making an abstract > > > "performance domain" which is the dvfs analogue to generic power > > > domains. This a reasonable split since gpd are good for idle power > > > savings (e.g. clock gate, power gate, sleep state, etc) and "perf > > > domains" would be good for active power savings (dvfs). > > > > > > Having a generic container for performance domains might make a good > > > place to stuff all of this glue logic that we keep running into (e.g. > > > CPU and GPU max frequencies that are related), and it might make another > > > nice knob for the thermal folks to use. > > > > This sounds like one level higher abstraction that we are speaking of > > here? I was'nt intending to solve the bigger picture problem here - > > just an abstraction level that might allow reusablity for multiple > > SoCs. In fact, having an abstraction away for voltage domain(which may > > consist of multiple regulators and any SoC specific magic) purely > > allows us to move towards a direction you mention here. > > > > > > > > For the case of the OMAP voltage domains, it would be a place to stuff > > > all of the VC/VP -> ABB -> Smart Reflex AVS stuff. > > > > > > > Unfortunately, I dont completely comprehend objection we have to this > > approach (other than an higher level abstraction is needed) and if we > > do have an objection, what is the alternate approach should be for > > representing hardware which this series attempts to present. > > I think the following is around the lines of your thought direction - > if Rafael or others have comments on the following approach, it'd be a > good starting point for me to progress. > > -->8-- > From 62e50b9f920495db88e5594aa6bceb52e83a443d Mon Sep 17 00:00:00 2001 > From: Nishanth Menon <nm@ti.com> > Date: Wed, 26 Feb 2014 10:59:59 -0600 > Subject: [PATCH] PM / Runtime: introduce active power management callbacks > for pm_domain > > dev_pm_domain currently handles just device idle power management > using the generic pm_runtime_get|put and related family of functions. > > Logically with appropriate pm_domain hooks this can translate to > hardware specific clock and related operations. Given that pm_domains > may contain this information, this provides an opportunity to extend > current pm_runtime do dynamic power operations as well. > > What this means for drivers is as follows: > > Today, drivers(with some level of complexity) do: > pm_runtime_get_sync(dev); > clk = clk_get(dev, "name"); > old_rate = clk_get_rate(clk); > ... > clk_set_rate(clk, new_rate); > ... > clk_put(clk); > pm_runtime_get_sync(dev); > > Instead, on pm_domains that can handle this as part of > pm_domain->active_ops functions, They can now do the following: > pm_runtime_get_sync(dev); > old_rate = pm_runtime_get_rate(dev); > ... > pm_runtime_set_rate(dev, new_rate); > ... > pm_runtime_put_sync(dev); > > Obviously, this'd work for devices that handle a single main > functional clock, but this could reduce complexity of drivers having > to deal with power management details to have pm_runtime as the main > point of interface. > > CAVEAT: For power domains that are capable of handling multiple > clocks (example on OMAP, where there are the concepts of interface, > functional and optional clocks per block), appropriate handling will > be necessary from pm_domain callbacks. So, the question about which > clock rate is being controlled or returned to is entirely upto the > pm_domain implementation. > > On the otherhand, we can debate about defining and querying ACPI style > "Performance state" instead of frequencies and wrap P-states inside > or the other way around.. but given that majority of drivers using > pm_runtime would rather be interested in frequencies and my naieve > belief that we can index P-states with frequencies, kind of influenced > my choice here of proposing frequencies as base query parameter.. > ofcourse, debate is still open here. > > Yes, we can still debate if providing yet another wrapper on top of > clock APIs makes sense at all as well. > > Nyet-signed-off-by: Nishanth Menon <nm@ti.com> > --- > drivers/base/power/runtime.c | 101 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/pm.h | 25 +++++++++-- > include/linux/pm_runtime.h | 21 +++++++++ > 3 files changed, 143 insertions(+), 4 deletions(-) > > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c > index 72e00e6..ef230b4 100644 > --- a/drivers/base/power/runtime.c > +++ b/drivers/base/power/runtime.c > @@ -1401,3 +1401,104 @@ void pm_runtime_remove(struct device *dev) > if (dev->power.irq_safe && dev->parent) > pm_runtime_put(dev->parent); > } > + > +/** > + * pm_runtime_get_rate() - Returns the device operational frequency > + * @dev: Device to handle > + * @rate: Returns rate in Hz. > + * > + * Returns appropriate error value in case of error conditions, else > + * returns 0 and rate is updated. The pm_domain logic does all the necessary > + * operation (which may consider magic hardware stuff) to provide the rate. > + * > + * NOTE: the rate returned is a snapshot and in many cases just a bypass > + * to clk api to set the rate. > + */ > +int pm_runtime_get_rate(struct device *dev, unsigned long *rate) > +{ > + unsigned long flags; > + int error = -ENOSYS; > + > + if (!rate || !dev) > + return -EINVAL; > + > + spin_lock_irqsave(&dev->power.lock, flags); > + if (!pm_runtime_active(dev)) { > + error = -EINVAL; > + goto out; > + } > + > + if (dev->pm_domain && dev->pm_domain->active_ops.get_rate) > + error = dev->pm_domain->active_ops.get_rate(dev, rate); > +out: > + spin_unlock_irqrestore(&dev->power.lock, flags); > + > + return error; > +} IMHO coupling device drivers even more with pm_runtime is wrong, and Kevin Hilman seems to agree [1]. I would much rather go with Nishanth's initial approach of subscribing to clock notifiers. They are, after all, supposed to tell the kernel about any clock changes. In just so happens that in the case discussed in this thread, OMAP needs to change voltages to match clock frequency and, IMHO, using clock notifiers for that is correct. The sematics are well defined and it's something which has been in the tree for quite some time. [1] https://lkml.org/lkml/2014/1/30/469
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 72e00e6..ef230b4 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -1401,3 +1401,104 @@ void pm_runtime_remove(struct device *dev) if (dev->power.irq_safe && dev->parent) pm_runtime_put(dev->parent); } + +/** + * pm_runtime_get_rate() - Returns the device operational frequency + * @dev: Device to handle + * @rate: Returns rate in Hz. + * + * Returns appropriate error value in case of error conditions, else + * returns 0 and rate is updated. The pm_domain logic does all the necessary + * operation (which may consider magic hardware stuff) to provide the rate. + * + * NOTE: the rate returned is a snapshot and in many cases just a bypass + * to clk api to set the rate. + */ +int pm_runtime_get_rate(struct device *dev, unsigned long *rate) +{ + unsigned long flags; + int error = -ENOSYS; + + if (!rate || !dev) + return -EINVAL; + + spin_lock_irqsave(&dev->power.lock, flags); + if (!pm_runtime_active(dev)) { + error = -EINVAL; + goto out; + } + + if (dev->pm_domain && dev->pm_domain->active_ops.get_rate) + error = dev->pm_domain->active_ops.get_rate(dev, rate); +out: + spin_unlock_irqrestore(&dev->power.lock, flags); + + return error; +} + +/** + * pm_runtime_set_rate() - Set a specific rate for the device operation + * @dev: Device to handle + * @rate: Rate to set in Hz + * + * Returns appropriate error value in case of error conditions, else + * returns 0. The pm_domain logic does all the necessary operation (which + * may include voltage scale operations or other magic hardware stuff) to + * achieve the operation. It is guarenteed that the requested rate is achieved + * on returning from this function if return value is 0. + */ +int pm_runtime_set_rate(struct device *dev, unsigned long rate) +{ + unsigned long flags; + int error = -ENOSYS; + + if (!rate || !dev) + return -EINVAL; + + spin_lock_irqsave(&dev->power.lock, flags); + if (!pm_runtime_active(dev)) { + error = -EINVAL; + goto out; + } + + if (dev->pm_domain && dev->pm_domain->active_ops.set_rate) + error = dev->pm_domain->active_ops.set_rate(dev, rate); +out: + spin_unlock_irqrestore(&dev->power.lock, flags); + + return error; +} + +/** + * pm_runtime_get_transition_latency() - determine transition latency` + * @dev: Device to handle + * @from_rate: Transition from which rate + * @to_rate: Transition to which rate + * + * Returns appropriate error value in case of error conditions, else + * returns the latency in uSecs for transition between two given rates + */ +int pm_runtime_get_transition_latency(struct device *dev, + unsigned long from_rate, + unsigned long to_rate) +{ + unsigned long flags; + int error = -ENOSYS; + + if (!from_rate || !to_rate || !dev) + return -EINVAL; + + spin_lock_irqsave(&dev->power.lock, flags); + if (!pm_runtime_active(dev)) { + error = -EINVAL; + goto out; + } + + if (dev->pm_domain && dev->pm_domain->active_ops.get_transition_latency) + error = dev->pm_domain->active_ops.get_transition_latency(dev, + from_rate, to_rate); +out: + spin_unlock_irqrestore(&dev->power.lock, flags); + + return error; +} diff --git a/include/linux/pm.h b/include/linux/pm.h index 8c6583a..f907b27 100644 --- a/include/linux/pm.h +++ b/include/linux/pm.h @@ -299,6 +299,20 @@ struct dev_pm_ops { int (*runtime_idle)(struct device *dev); }; +/** + * struct dev_pm_active_ops - Active power management operations + * @get_rate: get the current operational frequency + * @set_rate: set the current operational frequency + * @get_transition_latency: get the transition latency in uSeconds + */ +struct dev_pm_active_ops { + int (*get_rate)(struct device *dev, unsigned long *rate); + int (*set_rate)(struct device *dev, unsigned long rate); + int (*get_transition_latency)(struct device *dev, + unsigned long from_rate, + unsigned long to_rate); +}; + #ifdef CONFIG_PM_SLEEP #define SET_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \ .suspend = suspend_fn, \ @@ -589,13 +603,16 @@ extern void update_pm_runtime_accounting(struct device *dev); extern int dev_pm_get_subsys_data(struct device *dev); extern int dev_pm_put_subsys_data(struct device *dev); -/* - * Power domains provide callbacks that are executed during system suspend, - * hibernation, system resume and during runtime PM transitions along with - * subsystem-level and driver-level callbacks. +/** + * struct dev_pm_domain - power domain information + * @ops: Power domains provide callbacks that are executed during system + * suspend, hibernation, system resume and during runtime PM transitions + * along with subsystem-level and driver-level callbacks. + * @active_ops: Active operational callbacks */ struct dev_pm_domain { struct dev_pm_ops ops; + struct dev_pm_active_ops active_ops; }; /* diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h index 16c9a62..731a6e4 100644 --- a/include/linux/pm_runtime.h +++ b/include/linux/pm_runtime.h @@ -112,6 +112,11 @@ static inline void pm_runtime_mark_last_busy(struct device *dev) ACCESS_ONCE(dev->power.last_busy) = jiffies; } +extern int pm_runtime_get_rate(struct device *dev, unsigned long *rate); +extern int pm_runtime_set_rate(struct device *dev, unsigned long rate); +extern int pm_runtime_get_transition_latency(struct device *dev, + unsigned long from_rate, + unsigned long to_rate); #else /* !CONFIG_PM_RUNTIME */ static inline int __pm_runtime_idle(struct device *dev, int rpmflags) @@ -162,6 +167,22 @@ static inline unsigned long pm_runtime_autosuspend_expiration( static inline void pm_runtime_set_memalloc_noio(struct device *dev, bool enable){} +static inline int pm_runtime_get_rate(struct device *dev, unsigned long *rate) +{ + return -ENOSYS; +} + +static inline int pm_runtime_set_rate(struct device *dev, unsigned long rate) +{ + return -ENOSYS; +} + +static inline int pm_runtime_get_transition_latency(struct device *dev, + unsigned long from_rate, + unsigned long to_rate) +{ + return -ENOSYS; +} #endif /* !CONFIG_PM_RUNTIME */ static inline int pm_runtime_idle(struct device *dev)