original development tree for Linux kernel GTP module; now long in mainline.
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/*
* Copyright (c) 2013 ARM/Linaro
*
* Authors: Daniel Lezcano <daniel.lezcano@linaro.org>
* Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
* Nicolas Pitre <nicolas.pitre@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Maintainer: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
* Maintainer: Daniel Lezcano <daniel.lezcano@linaro.org>
*/
#include <linux/cpuidle.h>
#include <linux/cpu_pm.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/cpuidle.h>
#include <asm/mcpm.h>
#include <asm/smp_plat.h>
#include <asm/suspend.h>
static int bl_enter_powerdown(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int idx);
/*
* NB: Owing to current menu governor behaviour big and LITTLE
* index 1 states have to define exit_latency and target_residency for
* cluster state since, when all CPUs in a cluster hit it, the cluster
* can be shutdown. This means that when a single CPU enters this state
* the exit_latency and target_residency values are somewhat overkill.
* There is no notion of cluster states in the menu governor, so CPUs
* have to define CPU states where possibly the cluster will be shutdown
* depending on the state of other CPUs. idle states entry and exit happen
* at random times; however the cluster state provides target_residency
* values as if all CPUs in a cluster enter the state at once; this is
* somewhat optimistic and behaviour should be fixed either in the governor
* or in the MCPM back-ends.
* To make this driver 100% generic the number of states and the exit_latency
* target_residency values must be obtained from device tree bindings.
*
* exit_latency: refers to the TC2 vexpress test chip and depends on the
* current cluster operating point. It is the time it takes to get the CPU
* up and running when the CPU is powered up on cluster wake-up from shutdown.
* Current values for big and LITTLE clusters are provided for clusters
* running at default operating points.
*
* target_residency: it is the minimum amount of time the cluster has
* to be down to break even in terms of power consumption. cluster
* shutdown has inherent dynamic power costs (L2 writebacks to DRAM
* being the main factor) that depend on the current operating points.
* The current values for both clusters are provided for a CPU whose half
* of L2 lines are dirty and require cleaning to DRAM, and takes into
* account leakage static power values related to the vexpress TC2 testchip.
*/
static struct cpuidle_driver bl_idle_little_driver = {
.name = "little_idle",
.owner = THIS_MODULE,
.states[0] = ARM_CPUIDLE_WFI_STATE,
.states[1] = {
.enter = bl_enter_powerdown,
.exit_latency = 700,
.target_residency = 2500,
.flags = CPUIDLE_FLAG_TIME_VALID |
CPUIDLE_FLAG_TIMER_STOP,
.name = "C1",
.desc = "ARM little-cluster power down",
},
.state_count = 2,
};
static struct cpuidle_driver bl_idle_big_driver = {
.name = "big_idle",
.owner = THIS_MODULE,
.states[0] = ARM_CPUIDLE_WFI_STATE,
.states[1] = {
.enter = bl_enter_powerdown,
.exit_latency = 500,
.target_residency = 2000,
.flags = CPUIDLE_FLAG_TIME_VALID |
CPUIDLE_FLAG_TIMER_STOP,
.name = "C1",
.desc = "ARM big-cluster power down",
},
.state_count = 2,
};
/*
* notrace prevents trace shims from getting inserted where they
* should not. Global jumps and ldrex/strex must not be inserted
* in power down sequences where caches and MMU may be turned off.
*/
static int notrace bl_powerdown_finisher(unsigned long arg)
{
/* MCPM works with HW CPU identifiers */
unsigned int mpidr = read_cpuid_mpidr();
unsigned int cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
unsigned int cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
mcpm_set_entry_vector(cpu, cluster, cpu_resume);
/*
* Residency value passed to mcpm_cpu_suspend back-end
* has to be given clear semantics. Set to 0 as a
* temporary value.
*/
mcpm_cpu_suspend(0);
/* return value != 0 means failure */
return 1;
}
/**
* bl_enter_powerdown - Programs CPU to enter the specified state
* @dev: cpuidle device
* @drv: The target state to be programmed
* @idx: state index
*
* Called from the CPUidle framework to program the device to the
* specified target state selected by the governor.
*/
static int bl_enter_powerdown(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int idx)
{
cpu_pm_enter();
cpu_suspend(0, bl_powerdown_finisher);
/* signals the MCPM core that CPU is out of low power state */
mcpm_cpu_powered_up();
cpu_pm_exit();
return idx;
}
static int __init bl_idle_driver_init(struct cpuidle_driver *drv, int cpu_id)
{
struct cpuinfo_arm *cpu_info;
struct cpumask *cpumask;
unsigned long cpuid;
int cpu;
cpumask = kzalloc(cpumask_size(), GFP_KERNEL);
if (!cpumask)
return -ENOMEM;
for_each_possible_cpu(cpu) {
cpu_info = &per_cpu(cpu_data, cpu);
cpuid = is_smp() ? cpu_info->cpuid : read_cpuid_id();
/* read cpu id part number */
if ((cpuid & 0xFFF0) == cpu_id)
cpumask_set_cpu(cpu, cpumask);
}
drv->cpumask = cpumask;
return 0;
}
static int __init bl_idle_init(void)
{
int ret;
/*
* Initialize the driver just for a compliant set of machines
*/
if (!of_machine_is_compatible("arm,vexpress,v2p-ca15_a7"))
return -ENODEV;
/*
* For now the differentiation between little and big cores
* is based on the part number. A7 cores are considered little
* cores, A15 are considered big cores. This distinction may
* evolve in the future with a more generic matching approach.
*/
ret = bl_idle_driver_init(&bl_idle_little_driver,
ARM_CPU_PART_CORTEX_A7);
if (ret)
return ret;
ret = bl_idle_driver_init(&bl_idle_big_driver, ARM_CPU_PART_CORTEX_A15);
if (ret)
goto out_uninit_little;
ret = cpuidle_register(&bl_idle_little_driver, NULL);
if (ret)
goto out_uninit_big;
ret = cpuidle_register(&bl_idle_big_driver, NULL);
if (ret)
goto out_unregister_little;
return 0;
out_unregister_little:
cpuidle_unregister(&bl_idle_little_driver);
out_uninit_big:
kfree(bl_idle_big_driver.cpumask);
out_uninit_little:
kfree(bl_idle_little_driver.cpumask);
return ret;
}
device_initcall(bl_idle_init);