[PATCH v8 3/8] drivers: cpuidle: implement DT based idle states infrastructure
Daniel Lezcano
daniel.lezcano at linaro.org
Wed Sep 3 06:25:39 PDT 2014
On 09/01/2014 05:28 PM, Lorenzo Pieralisi wrote:
> On most common ARM systems, the low-power states a CPU can be put into are
> not discoverable in HW and require device tree bindings to describe
> power down suspend operations and idle states parameters.
>
> In order to enable DT based idle states and configure idle drivers, this
> patch implements the bulk infrastructure required to parse the device tree
> idle states bindings and initialize the corresponding CPUidle driver states
> data.
>
> The parsing API accepts a start index that defines the first idle state
> that should be initialized by the parsing code in order to give new and
> legacy driver flexibility over which states should be parsed using the
> new DT mechanism.
>
> The idle states node(s) is obtained from the phandle list of the first cpu
> in the driver cpumask; the kernel checks that the idle state node phandle
> is the same for all CPUs in the driver cpumask before declaring the idle state
> as valid and start parsing its content.
>
> The idle state enter function pointer is initialized through DT match
> structures passed in by the CPUidle driver, so that ARM legacy code can
> cope with platform specific idle entry method based on compatible
> string matching and the code used to initialize the enter function pointer
> can be moved to the DT generic layer.
>
> Acked-by: Catalin Marinas <catalin.marinas at arm.com>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
nice !
Acked-by: Daniel Lezcano <daniel.lezcano at linaro.org>
> ---
> drivers/cpuidle/Kconfig | 3 +
> drivers/cpuidle/Makefile | 1 +
> drivers/cpuidle/dt_idle_states.c | 213 +++++++++++++++++++++++++++++++++++++++
> drivers/cpuidle/dt_idle_states.h | 7 ++
> 4 files changed, 224 insertions(+)
> create mode 100644 drivers/cpuidle/dt_idle_states.c
> create mode 100644 drivers/cpuidle/dt_idle_states.h
>
> diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
> index 32748c3..8deb934 100644
> --- a/drivers/cpuidle/Kconfig
> +++ b/drivers/cpuidle/Kconfig
> @@ -25,6 +25,9 @@ config CPU_IDLE_GOV_MENU
> bool "Menu governor (for tickless system)"
> default y
>
> +config DT_IDLE_STATES
> + bool
> +
> menu "ARM CPU Idle Drivers"
> depends on ARM
> source "drivers/cpuidle/Kconfig.arm"
> diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
> index 11edb31..002b653 100644
> --- a/drivers/cpuidle/Makefile
> +++ b/drivers/cpuidle/Makefile
> @@ -4,6 +4,7 @@
>
> obj-y += cpuidle.o driver.o governor.o sysfs.o governors/
> obj-$(CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED) += coupled.o
> +obj-$(CONFIG_DT_IDLE_STATES) += dt_idle_states.o
>
> ##################################################################################
> # ARM SoC drivers
> diff --git a/drivers/cpuidle/dt_idle_states.c b/drivers/cpuidle/dt_idle_states.c
> new file mode 100644
> index 0000000..52f4d11
> --- /dev/null
> +++ b/drivers/cpuidle/dt_idle_states.c
> @@ -0,0 +1,213 @@
> +/*
> + * DT idle states parsing code.
> + *
> + * Copyright (C) 2014 ARM Ltd.
> + * Author: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> + *
> + * 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.
> + */
> +
> +#define pr_fmt(fmt) "DT idle-states: " fmt
> +
> +#include <linux/cpuidle.h>
> +#include <linux/cpumask.h>
> +#include <linux/errno.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +
> +#include "dt_idle_states.h"
> +
> +static int init_state_node(struct cpuidle_state *idle_state,
> + const struct of_device_id *matches,
> + struct device_node *state_node)
> +{
> + int err;
> + const struct of_device_id *match_id;
> +
> + match_id = of_match_node(matches, state_node);
> + if (!match_id)
> + return -ENODEV;
> + /*
> + * CPUidle drivers are expected to initialize the const void *data
> + * pointer of the passed in struct of_device_id array to the idle
> + * state enter function.
> + */
> + idle_state->enter = match_id->data;
> +
> + err = of_property_read_u32(state_node, "wakeup-latency-us",
> + &idle_state->exit_latency);
> + if (err) {
> + u32 entry_latency, exit_latency;
> +
> + err = of_property_read_u32(state_node, "entry-latency-us",
> + &entry_latency);
> + if (err) {
> + pr_debug(" * %s missing entry-latency-us property\n",
> + state_node->full_name);
> + return -EINVAL;
> + }
> +
> + err = of_property_read_u32(state_node, "exit-latency-us",
> + &exit_latency);
> + if (err) {
> + pr_debug(" * %s missing exit-latency-us property\n",
> + state_node->full_name);
> + return -EINVAL;
> + }
> + /*
> + * If wakeup-latency-us is missing, default to entry+exit
> + * latencies as defined in idle states bindings
> + */
> + idle_state->exit_latency = entry_latency + exit_latency;
> + }
> +
> + err = of_property_read_u32(state_node, "min-residency-us",
> + &idle_state->target_residency);
> + if (err) {
> + pr_debug(" * %s missing min-residency-us property\n",
> + state_node->full_name);
> + return -EINVAL;
> + }
> +
> + idle_state->flags = CPUIDLE_FLAG_TIME_VALID;
> + if (of_property_read_bool(state_node, "local-timer-stop"))
> + idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
> + /*
> + * TODO:
> + * replace with kstrdup and pointer assignment when name
> + * and desc become string pointers
> + */
> + strncpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN - 1);
> + strncpy(idle_state->desc, state_node->name, CPUIDLE_DESC_LEN - 1);
> + return 0;
> +}
> +
> +/*
> + * Check that the idle state is uniform across all CPUs in the CPUidle driver
> + * cpumask
> + */
> +static bool idle_state_valid(struct device_node *state_node, unsigned int idx,
> + const cpumask_t *cpumask)
> +{
> + int cpu;
> + struct device_node *cpu_node, *curr_state_node;
> + bool valid = true;
> +
> + /*
> + * Compare idle state phandles for index idx on all CPUs in the
> + * CPUidle driver cpumask. Start from next logical cpu following
> + * cpumask_first(cpumask) since that's the CPU state_node was
> + * retrieved from. If a mismatch is found bail out straight
> + * away since we certainly hit a firmware misconfiguration.
> + */
> + for (cpu = cpumask_next(cpumask_first(cpumask), cpumask);
> + cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpumask)) {
> + cpu_node = of_cpu_device_node_get(cpu);
> + curr_state_node = of_parse_phandle(cpu_node, "cpu-idle-states",
> + idx);
> + if (state_node != curr_state_node)
> + valid = false;
> +
> + of_node_put(curr_state_node);
> + of_node_put(cpu_node);
> + if (!valid)
> + break;
> + }
> +
> + return valid;
> +}
> +
> +/**
> + * dt_init_idle_driver() - Parse the DT idle states and initialize the
> + * idle driver states array
> + * @drv: Pointer to CPU idle driver to be initialized
> + * @matches: Array of of_device_id match structures to search in for
> + * compatible idle state nodes. The data pointer for each valid
> + * struct of_device_id entry in the matches array must point to
> + * a function with the following signature, that corresponds to
> + * the CPUidle state enter function signature:
> + *
> + * int (*)(struct cpuidle_device *dev,
> + * struct cpuidle_driver *drv,
> + * int index);
> + *
> + * @start_idx: First idle state index to be initialized
> + *
> + * If DT idle states are detected and are valid the state count and states
> + * array entries in the cpuidle driver are initialized accordingly starting
> + * from index start_idx.
> + *
> + * Return: number of valid DT idle states parsed, <0 on failure
> + */
> +int dt_init_idle_driver(struct cpuidle_driver *drv,
> + const struct of_device_id *matches,
> + unsigned int start_idx)
> +{
> + struct cpuidle_state *idle_state;
> + struct device_node *state_node, *cpu_node;
> + int i, err = 0;
> + const cpumask_t *cpumask;
> + unsigned int state_idx = start_idx;
> +
> + if (state_idx >= CPUIDLE_STATE_MAX)
> + return -EINVAL;
> + /*
> + * We get the idle states for the first logical cpu in the
> + * driver mask (or cpu_possible_mask if the driver cpumask is not set)
> + * and we check through idle_state_valid() if they are uniform
> + * across CPUs, otherwise we hit a firmware misconfiguration.
> + */
> + cpumask = drv->cpumask ? : cpu_possible_mask;
> + cpu_node = of_cpu_device_node_get(cpumask_first(cpumask));
> +
> + for (i = 0; ; i++) {
> + state_node = of_parse_phandle(cpu_node, "cpu-idle-states", i);
> + if (!state_node)
> + break;
> +
> + if (!idle_state_valid(state_node, i, cpumask)) {
> + pr_warn("%s idle state not valid, bailing out\n",
> + state_node->full_name);
> + err = -EINVAL;
> + break;
> + }
> +
> + if (state_idx == CPUIDLE_STATE_MAX) {
> + pr_warn("State index reached static CPU idle driver states array size\n");
> + break;
> + }
> +
> + idle_state = &drv->states[state_idx++];
> + err = init_state_node(idle_state, matches, state_node);
> + if (err) {
> + pr_err("Parsing idle state node %s failed with err %d\n",
> + state_node->full_name, err);
> + err = -EINVAL;
> + break;
> + }
> + of_node_put(state_node);
> + }
> +
> + of_node_put(state_node);
> + of_node_put(cpu_node);
> + if (err)
> + return err;
> + /*
> + * Update the driver state count only if some valid DT idle states
> + * were detected
> + */
> + if (i)
> + drv->state_count = state_idx;
> +
> + /*
> + * Return the number of present and valid DT idle states, which can
> + * also be 0 on platforms with missing DT idle states or legacy DT
> + * configuration predating the DT idle states bindings.
> + */
> + return i;
> +}
> +EXPORT_SYMBOL_GPL(dt_init_idle_driver);
> diff --git a/drivers/cpuidle/dt_idle_states.h b/drivers/cpuidle/dt_idle_states.h
> new file mode 100644
> index 0000000..4818134
> --- /dev/null
> +++ b/drivers/cpuidle/dt_idle_states.h
> @@ -0,0 +1,7 @@
> +#ifndef __DT_IDLE_STATES
> +#define __DT_IDLE_STATES
> +
> +int dt_init_idle_driver(struct cpuidle_driver *drv,
> + const struct of_device_id *matches,
> + unsigned int start_idx);
> +#endif
>
--
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