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References: <20220210054947.170134-1-apatel@ventanamicro.com>
 <20220210054947.170134-7-apatel@ventanamicro.com> <CAOnJCUKmwk=VbwCtkjS_rxArMWhVExeRp4QkkjDUmcvJ69Bqqg@mail.gmail.com>
 <E1C6F0F1-1FC2-43ED-AD26-6F2B8925BF04@jrtc27.com>
In-Reply-To: <E1C6F0F1-1FC2-43ED-AD26-6F2B8925BF04@jrtc27.com>
From:   Atish Patra <atishp@atishpatra.org>
Date:   Wed, 16 Feb 2022 13:21:23 -0800
Message-ID: <CAOnJCULDh_eoY4i1rB9tLbaQQcY5tTYQqZOLj=kkpOSVCCNfpQ@mail.gmail.com>
Subject: Re: [PATCH v11 6/8] cpuidle: Add RISC-V SBI CPU idle driver
To:     Jessica Clarke <jrtc27@jrtc27.com>
Cc:     Anup Patel <apatel@ventanamicro.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Pavel Machek <pavel@ucw.cz>, Rob Herring <robh+dt@kernel.org>,
        Sandeep Tripathy <milun.tripathy@gmail.com>,
        Alistair Francis <Alistair.Francis@wdc.com>,
        Liush <liush@allwinnertech.com>,
        Anup Patel <anup@brainfault.org>,
        devicetree <devicetree@vger.kernel.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
        "open list:THERMAL" <linux-pm@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        kvm-riscv@lists.infradead.org
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On Wed, Feb 16, 2022 at 5:45 AM Jessica Clarke <jrtc27@jrtc27.com> wrote:
>
> On 16 Feb 2022, at 08:09, Atish Patra <atishp@atishpatra.org> wrote:
> >
> > On Wed, Feb 9, 2022 at 9:51 PM 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>
> >> ---
> >> 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
> >>
> >
> > For the SBI part,
> > Acked-by: Atish Patra <atishp@rivosinc.com>
> >
> > FYI..
> > SBI HSM suspend was included in SBI v0.3. The current version of the
> > SBI specification (v1.0-rc2)
> > is already frozen as per the RVI guidelines. All the comments received
> > during the public review period
> > have been addressed as well.
>
> Yet not all comments from *before* the public review period.
>

I guess you are talking about the following issue,
https://github.com/riscv-non-isa/riscv-sbi-doc/issues/82

The issues raised here concern only the legacy version(v0.1) which is
disabled from the kernel in the latest release.
I have left detailed comments on why no changes to the spec is necessary.

> Jess
>


-- 
Regards,
Atish