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Subject[RFC PATCH 6/8] cpuidle: Add RISC-V SBI CPU idle driver
Date
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>
---
MAINTAINERS | 8 +
drivers/cpuidle/Kconfig | 5 +
drivers/cpuidle/Kconfig.riscv | 15 +
drivers/cpuidle/Makefile | 4 +
drivers/cpuidle/cpuidle-sbi.c | 503 ++++++++++++++++++++++++++++++++++
5 files changed, 535 insertions(+)
create mode 100644 drivers/cpuidle/Kconfig.riscv
create mode 100644 drivers/cpuidle/cpuidle-sbi.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 667d03852191..eeeab188a8ac 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4641,6 +4641,14 @@ S: Supported
F: drivers/cpuidle/cpuidle-psci.h
F: drivers/cpuidle/cpuidle-psci-domain.c

+CPUIDLE DRIVER - RISC-V SBI
+M: Anup Patel <anup.patel@wdc.com>
+R: Sandeep Tripathy <milun.tripathy@gmail.com>
+L: linux-pm@vger.kernel.org
+L: linux-riscv@lists.infradead.org
+S: Supported
+F: drivers/cpuidle/cpuidle-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..a36922c18510 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-sbi.o
diff --git a/drivers/cpuidle/cpuidle-sbi.c b/drivers/cpuidle/cpuidle-sbi.c
new file mode 100644
index 000000000000..abbcabca0e91
--- /dev/null
+++ b/drivers/cpuidle/cpuidle-sbi.c
@@ -0,0 +1,503 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * RISC-V SBI CPU idle driver.
+ *
+ * Copyright (c) 2021 Western Digital Corporation or its affiliates.
+ */
+
+#define pr_fmt(fmt) "cpuidle-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_genpd_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_genpd_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 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;
+}
+
+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;
+}
+
+static struct dt_idle_genpd_ops sbi_genpd_ops = {
+ .parse_state_node = sbi_dt_parse_state_node,
+};
+
+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;
+ }
+ }
+
+ if (sbi_cpuidle_use_osi)
+ sbi_genpd_ops.power_off = sbi_cpuidle_pd_power_off;
+
+ /* Populate generic power domains from DT nodes */
+ pds_node = of_find_node_by_path("/cpus/sbi-power-domains");
+ if (pds_node) {
+ ret = dt_idle_genpd_probe(&sbi_genpd_ops, 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 HSM extension is available
+ * 2) SBI version is 0.3 or higher
+ */
+ if (sbi_major_version() < 0 ||
+ sbi_minor_version() < 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
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