Documentation/power/opp.rst

5 (C) 2009-2010 Nishanth Menon <nm@ti.com>, Texas Instruments Incorporated
20 -------------------------------------------------
22 Complex SoCs of today consists of a multiple sub-modules working in conjunction.
25 facilitate this, sub-modules in a SoC are grouped into domains, allowing some
31 OPPs.
39 We can represent these as three OPPs as the following {Hz, uV} tuples:
41 - {300000000, 1000000}
42 - {800000000, 1200000}
43 - {1000000000, 1300000}
46 ----------------------------------------
57  (users)	-> registers a set of default OPPs		-> (library)
58  SoC framework	-> modifies on required cases certain OPPs	-> OPP layer
59 		-> queries to search/retrieve information	->
62 framework registers a set of initial OPPs per device with the OPP layer. This
64 This initial list contains a set of OPPs that the framework expects to be safely
71 OPPs available or not available on each device based on various external
74 operations until that OPP could be re-enabled if possible.
77 operational functions operate only on available opps:
83 opp available as required.
94 The SoC implementation calls dev_pm_opp_add function iteratively to add OPPs per
96 optimally- typical numbers range to be less than 5. The list generated by
97 registering the OPPs is maintained by OPP library throughout the device
99 OPPs dynamically using the dev_pm_opp_enable / disable functions.
161 	  This is the only search function that operates on OPPs which are
186 	Example 2: A simplified implementation of a SoC cpufreq_driver->target::
206 fine grained dynamic control of which sets of OPPs are operationally available.
293 			 return -EINVAL;
295 			 return -EINVAL;
300 	Retrieve the number of available opps for a device
301 	Example: Lets say a co-processor in the SoC needs to know the available
329    |- device 1
330    |	|- opp 1 (availability, freq, voltage)
331    |	|- opp 2 ..
333    |	`- opp n ..
334    |- device 2
336    `- device m
340 representing the actual OPPs and domains are internal to the OPP library itself
346 	information, it also contains internal book keeping information required
366               +-----+        /- dev_pm_opp_enable
367   dev_pm_opp_add --> | opp | <-------
368     |         +-----+        \- dev_pm_opp_disable
369     \-------> domain_info(device)
372                /-- dev_pm_opp_find_freq_ceil  ---\   +-----+
373   domain_info<---- dev_pm_opp_find_freq_exact -----> | opp |
374                \-- dev_pm_opp_find_freq_floor ---/   +-----+
377   +-----+     /- dev_pm_opp_get_voltage
378   | opp | <---
379   +-----+     \- dev_pm_opp_get_freq
381   domain_info <- dev_pm_opp_get_opp_count