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