Mailing List Archive

This patch adds support for the Power State Coordination Interface
defined by ARM, allowing Linux to request CPU-centric power-management
operations from firmware implementing the PSCI protocol.

Signed-off-by: Will Deacon <will.deacon@arm.com>
---
arch/arm/Kconfig | 10 +++
arch/arm/include/asm/psci.h | 36 ++++++++
arch/arm/kernel/Makefile | 1 +
arch/arm/kernel/psci.c | 211 ++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 258 insertions(+)
create mode 100644 arch/arm/include/asm/psci.h
create mode 100644 arch/arm/kernel/psci.c

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 8c83d98..80d54b8 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1617,6 +1617,16 @@ config HOTPLUG_CPU
Say Y here to experiment with turning CPUs off and on. CPUs
can be controlled through /sys/devices/system/cpu.

+config ARM_PSCI
+ bool "Support for the ARM Power State Coordination Interface (PSCI)"
+ depends on CPU_V7
+ help
+ Say Y here if you want Linux to communicate with system firmware
+ implementing the PSCI specification for CPU-centric power
+ management operations described in ARM document number ARM DEN
+ 0022A ("Power State Coordination Interface System Software on
+ ARM processors").
+
config LOCAL_TIMERS
bool "Use local timer interrupts"
depends on SMP
diff --git a/arch/arm/include/asm/psci.h b/arch/arm/include/asm/psci.h
new file mode 100644
index 0000000..ce0dbe7
--- /dev/null
+++ b/arch/arm/include/asm/psci.h
@@ -0,0 +1,36 @@
+/*
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * Copyright (C) 2012 ARM Limited
+ */
+
+#ifndef __ASM_ARM_PSCI_H
+#define __ASM_ARM_PSCI_H
+
+#define PSCI_POWER_STATE_TYPE_STANDBY 0
+#define PSCI_POWER_STATE_TYPE_POWER_DOWN 1
+
+struct psci_power_state {
+ u16 id;
+ u8 type;
+ u8 affinity_level;
+};
+
+struct psci_operations {
+ int (*cpu_suspend)(struct psci_power_state state,
+ unsigned long entry_point);
+ int (*cpu_off)(struct psci_power_state state);
+ int (*cpu_on)(unsigned long cpuid, unsigned long entry_point);
+ int (*migrate)(unsigned long cpuid);
+};
+
+extern struct psci_operations psci_ops;
+
+#endif /* __ASM_ARM_PSCI_H */
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 5bbec7b..5f3338e 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -82,5 +82,6 @@ obj-$(CONFIG_DEBUG_LL) += debug.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o

obj-$(CONFIG_ARM_VIRT_EXT) += hyp-stub.o
+obj-$(CONFIG_ARM_PSCI) += psci.o

extra-y := $(head-y) vmlinux.lds
diff --git a/arch/arm/kernel/psci.c b/arch/arm/kernel/psci.c
new file mode 100644
index 0000000..3653164
--- /dev/null
+++ b/arch/arm/kernel/psci.c
@@ -0,0 +1,211 @@
+/*
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * Copyright (C) 2012 ARM Limited
+ *
+ * Author: Will Deacon <will.deacon@arm.com>
+ */
+
+#define pr_fmt(fmt) "psci: " fmt
+
+#include <linux/init.h>
+#include <linux/of.h>
+
+#include <asm/compiler.h>
+#include <asm/errno.h>
+#include <asm/opcodes-sec.h>
+#include <asm/opcodes-virt.h>
+#include <asm/psci.h>
+
+struct psci_operations psci_ops;
+
+static int (*invoke_psci_fn)(u32, u32, u32, u32);
+
+enum psci_function {
+ PSCI_FN_CPU_SUSPEND,
+ PSCI_FN_CPU_ON,
+ PSCI_FN_CPU_OFF,
+ PSCI_FN_MIGRATE,
+ PSCI_FN_MAX,
+};
+
+static u32 psci_function_id[PSCI_FN_MAX];
+
+#define PSCI_RET_SUCCESS 0
+#define PSCI_RET_EOPNOTSUPP -1
+#define PSCI_RET_EINVAL -2
+#define PSCI_RET_EPERM -3
+
+static int psci_to_linux_errno(int errno)
+{
+ switch (errno) {
+ case PSCI_RET_SUCCESS:
+ return 0;
+ case PSCI_RET_EOPNOTSUPP:
+ return -EOPNOTSUPP;
+ case PSCI_RET_EINVAL:
+ return -EINVAL;
+ case PSCI_RET_EPERM:
+ return -EPERM;
+ };
+
+ return -EINVAL;
+}
+
+#define PSCI_POWER_STATE_ID_MASK 0xffff
+#define PSCI_POWER_STATE_ID_SHIFT 0
+#define PSCI_POWER_STATE_TYPE_MASK 0x1
+#define PSCI_POWER_STATE_TYPE_SHIFT 16
+#define PSCI_POWER_STATE_AFFL_MASK 0x3
+#define PSCI_POWER_STATE_AFFL_SHIFT 24
+
+static u32 psci_power_state_pack(struct psci_power_state state)
+{
+ return ((state.id & PSCI_POWER_STATE_ID_MASK)
+ << PSCI_POWER_STATE_ID_SHIFT) |
+ ((state.type & PSCI_POWER_STATE_TYPE_MASK)
+ << PSCI_POWER_STATE_TYPE_SHIFT) |
+ ((state.affinity_level & PSCI_POWER_STATE_AFFL_MASK)
+ << PSCI_POWER_STATE_AFFL_SHIFT);
+}
+
+/*
+ * The following two functions are invoked via the invoke_psci_fn pointer
+ * and will not be inlined, allowing us to piggyback on the AAPCS.
+ */
+static noinline int __invoke_psci_fn_hvc(u32 function_id, u32 arg0, u32 arg1,
+ u32 arg2)
+{
+ asm volatile(
+ __asmeq("%0", "r0")
+ __asmeq("%1", "r1")
+ __asmeq("%2", "r2")
+ __asmeq("%3", "r3")
+ __HVC(0)
+ : "+r" (function_id)
+ : "r" (arg0), "r" (arg1), "r" (arg2));
+
+ return function_id;
+}
+
+static noinline int __invoke_psci_fn_smc(u32 function_id, u32 arg0, u32 arg1,
+ u32 arg2)
+{
+ asm volatile(
+ __asmeq("%0", "r0")
+ __asmeq("%1", "r1")
+ __asmeq("%2", "r2")
+ __asmeq("%3", "r3")
+ __SMC(0)
+ : "+r" (function_id)
+ : "r" (arg0), "r" (arg1), "r" (arg2));
+
+ return function_id;
+}
+
+static int psci_cpu_suspend(struct psci_power_state state,
+ unsigned long entry_point)
+{
+ int err;
+ u32 fn, power_state;
+
+ fn = psci_function_id[PSCI_FN_CPU_SUSPEND];
+ power_state = psci_power_state_pack(state);
+ err = invoke_psci_fn(fn, power_state, entry_point, 0);
+ return psci_to_linux_errno(err);
+}
+
+static int psci_cpu_off(struct psci_power_state state)
+{
+ int err;
+ u32 fn, power_state;
+
+ fn = psci_function_id[PSCI_FN_CPU_OFF];
+ power_state = psci_power_state_pack(state);
+ err = invoke_psci_fn(fn, power_state, 0, 0);
+ return psci_to_linux_errno(err);
+}
+
+static int psci_cpu_on(unsigned long cpuid, unsigned long entry_point)
+{
+ int err;
+ u32 fn;
+
+ fn = psci_function_id[PSCI_FN_CPU_ON];
+ err = invoke_psci_fn(fn, cpuid, entry_point, 0);
+ return psci_to_linux_errno(err);
+}
+
+static int psci_migrate(unsigned long cpuid)
+{
+ int err;
+ u32 fn;
+
+ fn = psci_function_id[PSCI_FN_MIGRATE];
+ err = invoke_psci_fn(fn, cpuid, 0, 0);
+ return psci_to_linux_errno(err);
+}
+
+static const struct of_device_id psci_of_match[] __initconst = {
+ { .compatible = "arm,psci", },
+ {},
+};
+
+static int __init psci_init(void)
+{
+ struct device_node *np;
+ const char *method;
+ u32 id;
+
+ np = of_find_matching_node(NULL, psci_of_match);
+ if (!np)
+ return 0;
+
+ pr_info("probing function IDs from device-tree\n");
+
+ if (of_property_read_string(np, "method", &method)) {
+ pr_warning("missing \"method\" property\n");
+ goto out_put_node;
+ }
+
+ if (!strcmp("hvc", method)) {
+ invoke_psci_fn = __invoke_psci_fn_hvc;
+ } else if (!strcmp("smc", method)) {
+ invoke_psci_fn = __invoke_psci_fn_smc;
+ } else {
+ pr_warning("invalid \"method\" property: %s\n", method);
+ goto out_put_node;
+ }
+
+ if (!of_property_read_u32(np, "cpu_suspend", &id)) {
+ psci_function_id[PSCI_FN_CPU_SUSPEND] = id;
+ psci_ops.cpu_suspend = psci_cpu_suspend;
+ }
+
+ if (!of_property_read_u32(np, "cpu_off", &id)) {
+ psci_function_id[PSCI_FN_CPU_OFF] = id;
+ psci_ops.cpu_off = psci_cpu_off;
+ }
+
+ if (!of_property_read_u32(np, "cpu_on", &id)) {
+ psci_function_id[PSCI_FN_CPU_ON] = id;
+ psci_ops.cpu_on = psci_cpu_on;
+ }
+
+ if (!of_property_read_u32(np, "migrate", &id)) {
+ psci_function_id[PSCI_FN_MIGRATE] = id;
+ psci_ops.migrate = psci_migrate;
+ }
+
+out_put_node:
+ of_node_put(np);
+ return 0;
+}
+early_initcall(psci_init);
--
1.8.0


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