Re: [PATCH v11 6/8] cpuidle: Add RISC-V SBI CPU idle driver

Anup Patel
2022-03-12T08:35:02Z

Hi Rafael,

On Thu, Feb 10, 2022 at 11:21 AM Anup Patel <apatel@ventanamicro.com> wrote:
>
> From: Anup Patel <anup.patel@wdc.com>
>
> The RISC-V SBI HSM extension provides HSM suspend call which can
> be used by Linux RISC-V to enter platform specific low-power state.
>
> This patch adds a CPU idle driver based on RISC-V SBI calls which
> will populate idle states from device tree and use SBI calls to
> entry these idle states.
>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>

Does this driver look okay to you ?

Best Regards,
Anup Patel

> ---
> MAINTAINERS | 7 +
> drivers/cpuidle/Kconfig | 5 +
> drivers/cpuidle/Kconfig.riscv | 15 +
> drivers/cpuidle/Makefile | 4 +
> drivers/cpuidle/cpuidle-riscv-sbi.c | 627 ++++++++++++++++++++++++++++
> 5 files changed, 658 insertions(+)
> create mode 100644 drivers/cpuidle/Kconfig.riscv
> create mode 100644 drivers/cpuidle/cpuidle-riscv-sbi.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 39ece23e8d93..2ff0055a26a7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5058,6 +5058,13 @@ S: Supported
> F: drivers/cpuidle/dt_idle_genpd.c
> F: drivers/cpuidle/dt_idle_genpd.h
>
> +CPUIDLE DRIVER - RISC-V SBI
> +M: Anup Patel <anup@brainfault.org>
> +L: linux-pm@vger.kernel.org
> +L: linux-riscv@lists.infradead.org
> +S: Maintained
> +F: drivers/cpuidle/cpuidle-riscv-sbi.c
> +
> CRAMFS FILESYSTEM
> M: Nicolas Pitre <nico@fluxnic.net>
> S: Maintained
> diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
> index f1afe7ab6b54..ff71dd662880 100644
> --- a/drivers/cpuidle/Kconfig
> +++ b/drivers/cpuidle/Kconfig
> @@ -66,6 +66,11 @@ depends on PPC
> source "drivers/cpuidle/Kconfig.powerpc"
> endmenu
>
> +menu "RISC-V CPU Idle Drivers"
> +depends on RISCV
> +source "drivers/cpuidle/Kconfig.riscv"
> +endmenu
> +
> config HALTPOLL_CPUIDLE
> tristate "Halt poll cpuidle driver"
> depends on X86 && KVM_GUEST
> diff --git a/drivers/cpuidle/Kconfig.riscv b/drivers/cpuidle/Kconfig.riscv
> new file mode 100644
> index 000000000000..78518c26af74
> --- /dev/null
> +++ b/drivers/cpuidle/Kconfig.riscv
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# RISC-V CPU Idle drivers
> +#
> +
> +config RISCV_SBI_CPUIDLE
> + bool "RISC-V SBI CPU idle Driver"
> + depends on RISCV_SBI
> + select DT_IDLE_STATES
> + select CPU_IDLE_MULTIPLE_DRIVERS
> + select DT_IDLE_GENPD if PM_GENERIC_DOMAINS_OF
> + help
> + Select this option to enable RISC-V SBI firmware based CPU idle
> + driver for RISC-V systems. This drivers also supports hierarchical
> + DT based layout of the idle state.
> diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
> index 11a26cef279f..d103342b7cfc 100644
> --- a/drivers/cpuidle/Makefile
> +++ b/drivers/cpuidle/Makefile
> @@ -35,3 +35,7 @@ obj-$(CONFIG_MIPS_CPS_CPUIDLE) += cpuidle-cps.o
> # POWERPC drivers
> obj-$(CONFIG_PSERIES_CPUIDLE) += cpuidle-pseries.o
> obj-$(CONFIG_POWERNV_CPUIDLE) += cpuidle-powernv.o
> +
> +###############################################################################
> +# RISC-V drivers
> +obj-$(CONFIG_RISCV_SBI_CPUIDLE) += cpuidle-riscv-sbi.o
> diff --git a/drivers/cpuidle/cpuidle-riscv-sbi.c b/drivers/cpuidle/cpuidle-riscv-sbi.c
> new file mode 100644
> index 000000000000..b459eda2cd37
> --- /dev/null
> +++ b/drivers/cpuidle/cpuidle-riscv-sbi.c
> @@ -0,0 +1,627 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * RISC-V SBI CPU idle driver.
> + *
> + * Copyright (c) 2021 Western Digital Corporation or its affiliates.
> + * Copyright (c) 2022 Ventana Micro Systems Inc.
> + */
> +
> +#define pr_fmt(fmt) "cpuidle-riscv-sbi: " fmt
> +
> +#include <linux/cpuidle.h>
> +#include <linux/cpumask.h>
> +#include <linux/cpu_pm.h>
> +#include <linux/cpu_cooling.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/slab.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_domain.h>
> +#include <linux/pm_runtime.h>
> +#include <asm/cpuidle.h>
> +#include <asm/sbi.h>
> +#include <asm/suspend.h>
> +
> +#include "dt_idle_states.h"
> +#include "dt_idle_genpd.h"
> +
> +struct sbi_cpuidle_data {
> + u32 *states;
> + struct device *dev;
> +};
> +
> +struct sbi_domain_state {
> + bool available;
> + u32 state;
> +};
> +
> +static DEFINE_PER_CPU_READ_MOSTLY(struct sbi_cpuidle_data, sbi_cpuidle_data);
> +static DEFINE_PER_CPU(struct sbi_domain_state, domain_state);
> +static bool sbi_cpuidle_use_osi;
> +static bool sbi_cpuidle_use_cpuhp;
> +static bool sbi_cpuidle_pd_allow_domain_state;
> +
> +static inline void sbi_set_domain_state(u32 state)
> +{
> + struct sbi_domain_state *data = this_cpu_ptr(&domain_state);
> +
> + data->available = true;
> + data->state = state;
> +}
> +
> +static inline u32 sbi_get_domain_state(void)
> +{
> + struct sbi_domain_state *data = this_cpu_ptr(&domain_state);
> +
> + return data->state;
> +}
> +
> +static inline void sbi_clear_domain_state(void)
> +{
> + struct sbi_domain_state *data = this_cpu_ptr(&domain_state);
> +
> + data->available = false;
> +}
> +
> +static inline bool sbi_is_domain_state_available(void)
> +{
> + struct sbi_domain_state *data = this_cpu_ptr(&domain_state);
> +
> + return data->available;
> +}
> +
> +static int sbi_suspend_finisher(unsigned long suspend_type,
> + unsigned long resume_addr,
> + unsigned long opaque)
> +{
> + struct sbiret ret;
> +
> + ret = sbi_ecall(SBI_EXT_HSM, SBI_EXT_HSM_HART_SUSPEND,
> + suspend_type, resume_addr, opaque, 0, 0, 0);
> +
> + return (ret.error) ? sbi_err_map_linux_errno(ret.error) : 0;
> +}
> +
> +static int sbi_suspend(u32 state)
> +{
> + if (state & SBI_HSM_SUSP_NON_RET_BIT)
> + return cpu_suspend(state, sbi_suspend_finisher);
> + else
> + return sbi_suspend_finisher(state, 0, 0);
> +}
> +
> +static int sbi_cpuidle_enter_state(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int idx)
> +{
> + u32 *states = __this_cpu_read(sbi_cpuidle_data.states);
> +
> + return CPU_PM_CPU_IDLE_ENTER_PARAM(sbi_suspend, idx, states[idx]);
> +}
> +
> +static int __sbi_enter_domain_idle_state(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int idx,
> + bool s2idle)
> +{
> + struct sbi_cpuidle_data *data = this_cpu_ptr(&sbi_cpuidle_data);
> + u32 *states = data->states;
> + struct device *pd_dev = data->dev;
> + u32 state;
> + int ret;
> +
> + ret = cpu_pm_enter();
> + if (ret)
> + return -1;
> +
> + /* Do runtime PM to manage a hierarchical CPU toplogy. */
> + rcu_irq_enter_irqson();
> + if (s2idle)
> + dev_pm_genpd_suspend(pd_dev);
> + else
> + pm_runtime_put_sync_suspend(pd_dev);
> + rcu_irq_exit_irqson();
> +
> + if (sbi_is_domain_state_available())
> + state = sbi_get_domain_state();
> + else
> + state = states[idx];
> +
> + ret = sbi_suspend(state) ? -1 : idx;
> +
> + rcu_irq_enter_irqson();
> + if (s2idle)
> + dev_pm_genpd_resume(pd_dev);
> + else
> + pm_runtime_get_sync(pd_dev);
> + rcu_irq_exit_irqson();
> +
> + cpu_pm_exit();
> +
> + /* Clear the domain state to start fresh when back from idle. */
> + sbi_clear_domain_state();
> + return ret;
> +}
> +
> +static int sbi_enter_domain_idle_state(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int idx)
> +{
> + return __sbi_enter_domain_idle_state(dev, drv, idx, false);
> +}
> +
> +static int sbi_enter_s2idle_domain_idle_state(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv,
> + int idx)
> +{
> + return __sbi_enter_domain_idle_state(dev, drv, idx, true);
> +}
> +
> +static int sbi_cpuidle_cpuhp_up(unsigned int cpu)
> +{
> + struct device *pd_dev = __this_cpu_read(sbi_cpuidle_data.dev);
> +
> + if (pd_dev)
> + pm_runtime_get_sync(pd_dev);
> +
> + return 0;
> +}
> +
> +static int sbi_cpuidle_cpuhp_down(unsigned int cpu)
> +{
> + struct device *pd_dev = __this_cpu_read(sbi_cpuidle_data.dev);
> +
> + if (pd_dev) {
> + pm_runtime_put_sync(pd_dev);
> + /* Clear domain state to start fresh at next online. */
> + sbi_clear_domain_state();
> + }
> +
> + return 0;
> +}
> +
> +static void sbi_idle_init_cpuhp(void)
> +{
> + int err;
> +
> + if (!sbi_cpuidle_use_cpuhp)
> + return;
> +
> + err = cpuhp_setup_state_nocalls(CPUHP_AP_CPU_PM_STARTING,
> + "cpuidle/sbi:online",
> + sbi_cpuidle_cpuhp_up,
> + sbi_cpuidle_cpuhp_down);
> + if (err)
> + pr_warn("Failed %d while setup cpuhp state\n", err);
> +}
> +
> +static const struct of_device_id sbi_cpuidle_state_match[] = {
> + { .compatible = "riscv,idle-state",
> + .data = sbi_cpuidle_enter_state },
> + { },
> +};
> +
> +static bool sbi_suspend_state_is_valid(u32 state)
> +{
> + if (state > SBI_HSM_SUSPEND_RET_DEFAULT &&
> + state < SBI_HSM_SUSPEND_RET_PLATFORM)
> + return false;
> + if (state > SBI_HSM_SUSPEND_NON_RET_DEFAULT &&
> + state < SBI_HSM_SUSPEND_NON_RET_PLATFORM)
> + return false;
> + return true;
> +}
> +
> +static int sbi_dt_parse_state_node(struct device_node *np, u32 *state)
> +{
> + int err = of_property_read_u32(np, "riscv,sbi-suspend-param", state);
> +
> + if (err) {
> + pr_warn("%pOF missing riscv,sbi-suspend-param property\n", np);
> + return err;
> + }
> +
> + if (!sbi_suspend_state_is_valid(*state)) {
> + pr_warn("Invalid SBI suspend state %#x\n", *state);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int sbi_dt_cpu_init_topology(struct cpuidle_driver *drv,
> + struct sbi_cpuidle_data *data,
> + unsigned int state_count, int cpu)
> +{
> + /* Currently limit the hierarchical topology to be used in OSI mode. */
> + if (!sbi_cpuidle_use_osi)
> + return 0;
> +
> + data->dev = dt_idle_attach_cpu(cpu, "sbi");
> + if (IS_ERR_OR_NULL(data->dev))
> + return PTR_ERR_OR_ZERO(data->dev);
> +
> + /*
> + * Using the deepest state for the CPU to trigger a potential selection
> + * of a shared state for the domain, assumes the domain states are all
> + * deeper states.
> + */
> + drv->states[state_count - 1].enter = sbi_enter_domain_idle_state;
> + drv->states[state_count - 1].enter_s2idle =
> + sbi_enter_s2idle_domain_idle_state;
> + sbi_cpuidle_use_cpuhp = true;
> +
> + return 0;
> +}
> +
> +static int sbi_cpuidle_dt_init_states(struct device *dev,
> + struct cpuidle_driver *drv,
> + unsigned int cpu,
> + unsigned int state_count)
> +{
> + struct sbi_cpuidle_data *data = per_cpu_ptr(&sbi_cpuidle_data, cpu);
> + struct device_node *state_node;
> + struct device_node *cpu_node;
> + u32 *states;
> + int i, ret;
> +
> + cpu_node = of_cpu_device_node_get(cpu);
> + if (!cpu_node)
> + return -ENODEV;
> +
> + states = devm_kcalloc(dev, state_count, sizeof(*states), GFP_KERNEL);
> + if (!states) {
> + ret = -ENOMEM;
> + goto fail;
> + }
> +
> + /* Parse SBI specific details from state DT nodes */
> + for (i = 1; i < state_count; i++) {
> + state_node = of_get_cpu_state_node(cpu_node, i - 1);
> + if (!state_node)
> + break;
> +
> + ret = sbi_dt_parse_state_node(state_node, &states[i]);
> + of_node_put(state_node);
> +
> + if (ret)
> + return ret;
> +
> + pr_debug("sbi-state %#x index %d\n", states[i], i);
> + }
> + if (i != state_count) {
> + ret = -ENODEV;
> + goto fail;
> + }
> +
> + /* Initialize optional data, used for the hierarchical topology. */
> + ret = sbi_dt_cpu_init_topology(drv, data, state_count, cpu);
> + if (ret < 0)
> + return ret;
> +
> + /* Store states in the per-cpu struct. */
> + data->states = states;
> +
> +fail:
> + of_node_put(cpu_node);
> +
> + return ret;
> +}
> +
> +static void sbi_cpuidle_deinit_cpu(int cpu)
> +{
> + struct sbi_cpuidle_data *data = per_cpu_ptr(&sbi_cpuidle_data, cpu);
> +
> + dt_idle_detach_cpu(data->dev);
> + sbi_cpuidle_use_cpuhp = false;
> +}
> +
> +static int sbi_cpuidle_init_cpu(struct device *dev, int cpu)
> +{
> + struct cpuidle_driver *drv;
> + unsigned int state_count = 0;
> + int ret = 0;
> +
> + drv = devm_kzalloc(dev, sizeof(*drv), GFP_KERNEL);
> + if (!drv)
> + return -ENOMEM;
> +
> + drv->name = "sbi_cpuidle";
> + drv->owner = THIS_MODULE;
> + drv->cpumask = (struct cpumask *)cpumask_of(cpu);
> +
> + /* RISC-V architectural WFI to be represented as state index 0. */
> + drv->states[0].enter = sbi_cpuidle_enter_state;
> + drv->states[0].exit_latency = 1;
> + drv->states[0].target_residency = 1;
> + drv->states[0].power_usage = UINT_MAX;
> + strcpy(drv->states[0].name, "WFI");
> + strcpy(drv->states[0].desc, "RISC-V WFI");
> +
> + /*
> + * If no DT idle states are detected (ret == 0) let the driver
> + * initialization fail accordingly since there is no reason to
> + * initialize the idle driver if only wfi is supported, the
> + * default archictectural back-end already executes wfi
> + * on idle entry.
> + */
> + ret = dt_init_idle_driver(drv, sbi_cpuidle_state_match, 1);
> + if (ret <= 0) {
> + pr_debug("HART%ld: failed to parse DT idle states\n",
> + cpuid_to_hartid_map(cpu));
> + return ret ? : -ENODEV;
> + }
> + state_count = ret + 1; /* Include WFI state as well */
> +
> + /* Initialize idle states from DT. */
> + ret = sbi_cpuidle_dt_init_states(dev, drv, cpu, state_count);
> + if (ret) {
> + pr_err("HART%ld: failed to init idle states\n",
> + cpuid_to_hartid_map(cpu));
> + return ret;
> + }
> +
> + ret = cpuidle_register(drv, NULL);
> + if (ret)
> + goto deinit;
> +
> + cpuidle_cooling_register(drv);
> +
> + return 0;
> +deinit:
> + sbi_cpuidle_deinit_cpu(cpu);
> + return ret;
> +}
> +
> +static void sbi_cpuidle_domain_sync_state(struct device *dev)
> +{
> + /*
> + * All devices have now been attached/probed to the PM domain
> + * topology, hence it's fine to allow domain states to be picked.
> + */
> + sbi_cpuidle_pd_allow_domain_state = true;
> +}
> +
> +#ifdef CONFIG_DT_IDLE_GENPD
> +
> +static int sbi_cpuidle_pd_power_off(struct generic_pm_domain *pd)
> +{
> + struct genpd_power_state *state = &pd->states[pd->state_idx];
> + u32 *pd_state;
> +
> + if (!state->data)
> + return 0;
> +
> + if (!sbi_cpuidle_pd_allow_domain_state)
> + return -EBUSY;
> +
> + /* OSI mode is enabled, set the corresponding domain state. */
> + pd_state = state->data;
> + sbi_set_domain_state(*pd_state);
> +
> + return 0;
> +}
> +
> +struct sbi_pd_provider {
> + struct list_head link;
> + struct device_node *node;
> +};
> +
> +static LIST_HEAD(sbi_pd_providers);
> +
> +static int sbi_pd_init(struct device_node *np)
> +{
> + struct generic_pm_domain *pd;
> + struct sbi_pd_provider *pd_provider;
> + struct dev_power_governor *pd_gov;
> + int ret = -ENOMEM, state_count = 0;
> +
> + pd = dt_idle_pd_alloc(np, sbi_dt_parse_state_node);
> + if (!pd)
> + goto out;
> +
> + pd_provider = kzalloc(sizeof(*pd_provider), GFP_KERNEL);
> + if (!pd_provider)
> + goto free_pd;
> +
> + pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_CPU_DOMAIN;
> +
> + /* Allow power off when OSI is available. */
> + if (sbi_cpuidle_use_osi)
> + pd->power_off = sbi_cpuidle_pd_power_off;
> + else
> + pd->flags |= GENPD_FLAG_ALWAYS_ON;
> +
> + /* Use governor for CPU PM domains if it has some states to manage. */
> + pd_gov = state_count > 0 ? &pm_domain_cpu_gov : NULL;
> +
> + ret = pm_genpd_init(pd, pd_gov, false);
> + if (ret)
> + goto free_pd_prov;
> +
> + ret = of_genpd_add_provider_simple(np, pd);
> + if (ret)
> + goto remove_pd;
> +
> + pd_provider->node = of_node_get(np);
> + list_add(&pd_provider->link, &sbi_pd_providers);
> +
> + pr_debug("init PM domain %s\n", pd->name);
> + return 0;
> +
> +remove_pd:
> + pm_genpd_remove(pd);
> +free_pd_prov:
> + kfree(pd_provider);
> +free_pd:
> + dt_idle_pd_free(pd);
> +out:
> + pr_err("failed to init PM domain ret=%d %pOF\n", ret, np);
> + return ret;
> +}
> +
> +static void sbi_pd_remove(void)
> +{
> + struct sbi_pd_provider *pd_provider, *it;
> + struct generic_pm_domain *genpd;
> +
> + list_for_each_entry_safe(pd_provider, it, &sbi_pd_providers, link) {
> + of_genpd_del_provider(pd_provider->node);
> +
> + genpd = of_genpd_remove_last(pd_provider->node);
> + if (!IS_ERR(genpd))
> + kfree(genpd);
> +
> + of_node_put(pd_provider->node);
> + list_del(&pd_provider->link);
> + kfree(pd_provider);
> + }
> +}
> +
> +static int sbi_genpd_probe(struct device_node *np)
> +{
> + struct device_node *node;
> + int ret = 0, pd_count = 0;
> +
> + if (!np)
> + return -ENODEV;
> +
> + /*
> + * Parse child nodes for the "#power-domain-cells" property and
> + * initialize a genpd/genpd-of-provider pair when it's found.
> + */
> + for_each_child_of_node(np, node) {
> + if (!of_find_property(node, "#power-domain-cells", NULL))
> + continue;
> +
> + ret = sbi_pd_init(node);
> + if (ret)
> + goto put_node;
> +
> + pd_count++;
> + }
> +
> + /* Bail out if not using the hierarchical CPU topology. */
> + if (!pd_count)
> + goto no_pd;
> +
> + /* Link genpd masters/subdomains to model the CPU topology. */
> + ret = dt_idle_pd_init_topology(np);
> + if (ret)
> + goto remove_pd;
> +
> + return 0;
> +
> +put_node:
> + of_node_put(node);
> +remove_pd:
> + sbi_pd_remove();
> + pr_err("failed to create CPU PM domains ret=%d\n", ret);
> +no_pd:
> + return ret;
> +}
> +
> +#else
> +
> +static inline int sbi_genpd_probe(struct device_node *np)
> +{
> + return 0;
> +}
> +
> +#endif
> +
> +static int sbi_cpuidle_probe(struct platform_device *pdev)
> +{
> + int cpu, ret;
> + struct cpuidle_driver *drv;
> + struct cpuidle_device *dev;
> + struct device_node *np, *pds_node;
> +
> + /* Detect OSI support based on CPU DT nodes */
> + sbi_cpuidle_use_osi = true;
> + for_each_possible_cpu(cpu) {
> + np = of_cpu_device_node_get(cpu);
> + if (np &&
> + of_find_property(np, "power-domains", NULL) &&
> + of_find_property(np, "power-domain-names", NULL)) {
> + continue;
> + } else {
> + sbi_cpuidle_use_osi = false;
> + break;
> + }
> + }
> +
> + /* Populate generic power domains from DT nodes */
> + pds_node = of_find_node_by_path("/cpus/power-domains");
> + if (pds_node) {
> + ret = sbi_genpd_probe(pds_node);
> + of_node_put(pds_node);
> + if (ret)
> + return ret;
> + }
> +
> + /* Initialize CPU idle driver for each CPU */
> + for_each_possible_cpu(cpu) {
> + ret = sbi_cpuidle_init_cpu(&pdev->dev, cpu);
> + if (ret) {
> + pr_debug("HART%ld: idle driver init failed\n",
> + cpuid_to_hartid_map(cpu));
> + goto out_fail;
> + }
> + }
> +
> + /* Setup CPU hotplut notifiers */
> + sbi_idle_init_cpuhp();
> +
> + pr_info("idle driver registered for all CPUs\n");
> +
> + return 0;
> +
> +out_fail:
> + while (--cpu >= 0) {
> + dev = per_cpu(cpuidle_devices, cpu);
> + drv = cpuidle_get_cpu_driver(dev);
> + cpuidle_unregister(drv);
> + sbi_cpuidle_deinit_cpu(cpu);
> + }
> +
> + return ret;
> +}
> +
> +static struct platform_driver sbi_cpuidle_driver = {
> + .probe = sbi_cpuidle_probe,
> + .driver = {
> + .name = "sbi-cpuidle",
> + .sync_state = sbi_cpuidle_domain_sync_state,
> + },
> +};
> +
> +static int __init sbi_cpuidle_init(void)
> +{
> + int ret;
> + struct platform_device *pdev;
> +
> + /*
> + * The SBI HSM suspend function is only available when:
> + * 1) SBI version is 0.3 or higher
> + * 2) SBI HSM extension is available
> + */
> + if ((sbi_spec_version < sbi_mk_version(0, 3)) ||
> + sbi_probe_extension(SBI_EXT_HSM) <= 0) {
> + pr_info("HSM suspend not available\n");
> + return 0;
> + }
> +
> + ret = platform_driver_register(&sbi_cpuidle_driver);
> + if (ret)
> + return ret;
> +
> + pdev = platform_device_register_simple("sbi-cpuidle",
> + -1, NULL, 0);
> + if (IS_ERR(pdev)) {
> + platform_driver_unregister(&sbi_cpuidle_driver);
> + return PTR_ERR(pdev);
> + }
> +
> + return 0;
> +}
> +device_initcall(sbi_cpuidle_init);
> --
> 2.25.1
>