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Subject[v3] cpuidle: add riscv cpuidle driver
Date
This patch adds a simple cpuidle driver for RISC-V systems using
the WFI state. Other states will be supported in the future.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: liush <liush@allwinnertech.com>
---
Changes in v3:
- fix the issue reported by kernel test robot
"drivers/cpuidle/cpuidle-riscv.c:22:12: warning: no previous prototype
for 'riscv_low_level_suspend_enter' [-Wmissing-prototypes]"
Changes in v2:
- call "mb()" before run "WFI" in cpu_do_idle
- modify commit description
- place "select CPU_IDLE" in alphabetical order
- replace "__asm__ __volatile__ ("wfi")" with "wait_for_interrupt()"
- delete "cpuidle.c",move "cpu_do_idle()" to cpuidle.h
- modify "arch_cpu_idle", "cpu_do_idle" can be called by
"arch_cpu_idle"
- fix space/tab issues
- modify riscv_low_level_suspend_enter to __weak mode

arch/riscv/Kconfig | 7 +++++
arch/riscv/include/asm/cpuidle.h | 16 ++++++++++++
arch/riscv/kernel/process.c | 3 ++-
drivers/cpuidle/Kconfig | 5 ++++
drivers/cpuidle/Kconfig.riscv | 11 ++++++++
drivers/cpuidle/Makefile | 4 +++
drivers/cpuidle/cpuidle-riscv.c | 55 ++++++++++++++++++++++++++++++++++++++++
7 files changed, 100 insertions(+), 1 deletion(-)
create mode 100644 arch/riscv/include/asm/cpuidle.h
create mode 100644 drivers/cpuidle/Kconfig.riscv
create mode 100644 drivers/cpuidle/cpuidle-riscv.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index df18372..799bf86 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -33,6 +33,7 @@ config RISCV
select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
select CLONE_BACKWARDS
select COMMON_CLK
+ select CPU_IDLE
select EDAC_SUPPORT
select GENERIC_ARCH_TOPOLOGY if SMP
select GENERIC_ATOMIC64 if !64BIT
@@ -407,6 +408,12 @@ config BUILTIN_DTB
depends on RISCV_M_MODE
depends on OF

+menu "CPU Power Management"
+
+source "drivers/cpuidle/Kconfig"
+
+endmenu
+
menu "Power management options"

source "kernel/power/Kconfig"
diff --git a/arch/riscv/include/asm/cpuidle.h b/arch/riscv/include/asm/cpuidle.h
new file mode 100644
index 00000000..599b810
--- /dev/null
+++ b/arch/riscv/include/asm/cpuidle.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __RISCV_CPUIDLE_H
+#define __RISCV_CPUIDLE_H
+
+static inline void cpu_do_idle(void)
+{
+ /*
+ * Add mb() here to ensure that all
+ * IO/MEM access are completed prior
+ * to enter WFI.
+ */
+ mb();
+ wait_for_interrupt();
+}
+
+#endif
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 2b97c49..5431aaa 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -21,6 +21,7 @@
#include <asm/string.h>
#include <asm/switch_to.h>
#include <asm/thread_info.h>
+#include <asm/cpuidle.h>

register unsigned long gp_in_global __asm__("gp");

@@ -35,7 +36,7 @@ extern asmlinkage void ret_from_kernel_thread(void);

void arch_cpu_idle(void)
{
- wait_for_interrupt();
+ cpu_do_idle();
local_irq_enable();
}

diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
index c0aeedd..f6be0fd 100644
--- a/drivers/cpuidle/Kconfig
+++ b/drivers/cpuidle/Kconfig
@@ -62,6 +62,11 @@ depends on PPC
source "drivers/cpuidle/Kconfig.powerpc"
endmenu

+menu "RISCV 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 00000000..7bec059
--- /dev/null
+++ b/drivers/cpuidle/Kconfig.riscv
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# RISCV CPU Idle drivers
+#
+config RISCV_CPUIDLE
+ bool "Generic RISCV CPU idle Driver"
+ select DT_IDLE_STATES
+ select CPU_IDLE_MULTIPLE_DRIVERS
+ help
+ Select this option to enable generic cpuidle driver for RISCV.
+ Now only support C0 State.
diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
index 26bbc5e..4c83c4e 100644
--- a/drivers/cpuidle/Makefile
+++ b/drivers/cpuidle/Makefile
@@ -34,3 +34,7 @@ obj-$(CONFIG_MIPS_CPS_CPUIDLE) += cpuidle-cps.o
# POWERPC drivers
obj-$(CONFIG_PSERIES_CPUIDLE) += cpuidle-pseries.o
obj-$(CONFIG_POWERNV_CPUIDLE) += cpuidle-powernv.o
+
+###############################################################################
+# RISCV drivers
+obj-$(CONFIG_RISCV_CPUIDLE) += cpuidle-riscv.o
diff --git a/drivers/cpuidle/cpuidle-riscv.c b/drivers/cpuidle/cpuidle-riscv.c
new file mode 100644
index 00000000..5dddcfa
--- /dev/null
+++ b/drivers/cpuidle/cpuidle-riscv.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RISC-V CPU idle driver.
+ *
+ * Copyright (C) 2020-2022 Allwinner Ltd
+ *
+ * Based on code - driver/cpuidle/cpuidle-at91.c
+ *
+ */
+#include <linux/cpuidle.h>
+#include <linux/cpumask.h>
+#include <linux/cpu_pm.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/platform_device.h>
+#include <asm/cpuidle.h>
+
+#define MAX_IDLE_STATES 1
+
+/* TODO: Implement deeper idle states */
+static int riscv_low_level_suspend_enter(int state)
+{
+ return 0;
+}
+
+/* Actual code that puts the SoC in different idle states */
+static int riscv_enter_idle(struct cpuidle_device *dev,
+ struct cpuidle_driver *drv,
+ int index)
+{
+ return CPU_PM_CPU_IDLE_ENTER_PARAM(riscv_low_level_suspend_enter,
+ index, 0);
+}
+
+static struct cpuidle_driver riscv_idle_driver = {
+ .name = "riscv_idle",
+ .owner = THIS_MODULE,
+ .states[0] = {
+ .enter = riscv_enter_idle,
+ .exit_latency = 1,
+ .target_residency = 1,
+ .name = "WFI",
+ .desc = "RISCV WFI",
+ },
+ .state_count = MAX_IDLE_STATES,
+};
+
+static int __init riscv_cpuidle_init(void)
+{
+ return cpuidle_register(&riscv_idle_driver, NULL);
+}
+
+device_initcall(riscv_cpuidle_init);
--
2.7.4
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