ARM: psci: add support for PSCI invocations from the kernel

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.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

4 files changed, 258 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 67874b82a4ed..96863b860641 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1620,6 +1620,16 @@ 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 000000000000..ce0dbe7c1625
--- /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 5bbec7b8183e..5f3338eacad2 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 000000000000..36531643cc2c
--- /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);