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authorVaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>2014-04-01 11:13:26 +0400
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-04-07 16:35:27 +0400
commitb3d627a5f2bf1a9a486f65af6f7c2ce0e09b3d12 (patch)
tree3b04d01b8e7ed6b48c28fed17479eec7225e3a75 /samples
parent0ca97886fece9e1acd71ade4ca3a250945c8fc8b (diff)
downloadlinux-b3d627a5f2bf1a9a486f65af6f7c2ce0e09b3d12.tar.xz
cpufreq: powernv: cpufreq driver for powernv platform
Backend driver to dynamically set voltage and frequency on IBM POWER non-virtualized platforms. Power management SPRs are used to set the required PState. This driver works in conjunction with cpufreq governors like 'ondemand' to provide a demand based frequency and voltage setting on IBM POWER non-virtualized platforms. PState table is obtained from OPAL v3 firmware through device tree. powernv_cpufreq back-end driver would parse the relevant device-tree nodes and initialise the cpufreq subsystem on powernv platform. The code was originally written by svaidy@linux.vnet.ibm.com. Over time it was modified to accomodate bug-fixes as well as updates to the the cpu-freq core. Relevant portions of the change logs corresponding to those modifications are noted below: * The policy->cpus needs to be populated in a hotplug-invariant manner instead of using cpu_sibling_mask() which varies with cpu-hotplug. This is because the cpufreq core code copies this content into policy->related_cpus mask which should not vary on cpu-hotplug. [Authored by srivatsa.bhat@linux.vnet.ibm.com] * Create a helper routine that can return the cpu-frequency for the corresponding pstate_id. Also, cache the values of the pstate_max, pstate_min and pstate_nominal and nr_pstates in a static structure so that they can be reused in the future to perform any validations. [Authored by ego@linux.vnet.ibm.com] * Create a driver attribute named cpuinfo_nominal_freq which creates a sysfs read-only file named cpuinfo_nominal_freq. Export the frequency corresponding to the nominal_pstate through this interface. Nominal frequency is the highest non-turbo frequency for the platform. This is generally used for setting governor policies from user space for optimal energy efficiency. [Authored by ego@linux.vnet.ibm.com] * Implement a powernv_cpufreq_get(unsigned int cpu) method which will return the current operating frequency. Export this via the sysfs interface cpuinfo_cur_freq by setting powernv_cpufreq_driver.get to powernv_cpufreq_get(). [Authored by ego@linux.vnet.ibm.com] [Change log updated by ego@linux.vnet.ibm.com] Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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