[RFC PATCH 1/8] RISC-V: Enable CPU_IDLE drivers

[Anup Patel <anup.patel@wdc.com>]

We force select CPU_PM and provide asm/cpuidle.h so that we can
use CPU IDLE drivers for Linux RISC-V kernel.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
 arch/riscv/Kconfig                |  7 +++++++
 arch/riscv/configs/defconfig      |  7 +++----
 arch/riscv/configs/rv32_defconfig |  4 ++--
 arch/riscv/include/asm/cpuidle.h  | 24 ++++++++++++++++++++++++
 arch/riscv/kernel/process.c       |  3 ++-
 5 files changed, 38 insertions(+), 7 deletions(-)
 create mode 100644 arch/riscv/include/asm/cpuidle.h

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index fe6862b06ead..4901200b6b6c 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -37,6 +37,7 @@ config RISCV
 	select CLONE_BACKWARDS
 	select CLINT_TIMER if !MMU
 	select COMMON_CLK
+	select CPU_PM if CPU_IDLE
 	select EDAC_SUPPORT
 	select GENERIC_ARCH_TOPOLOGY if SMP
 	select GENERIC_ATOMIC64 if !64BIT
@@ -430,4 +431,10 @@ source "kernel/power/Kconfig"
 
 endmenu
 
+menu "CPU Power Management"
+
+source "drivers/cpuidle/Kconfig"
+
+endmenu
+
 source "drivers/firmware/Kconfig"
diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
index 6c0625aa96c7..dc4927c0e44b 100644
--- a/arch/riscv/configs/defconfig
+++ b/arch/riscv/configs/defconfig
@@ -13,11 +13,13 @@ CONFIG_USER_NS=y
 CONFIG_CHECKPOINT_RESTORE=y
 CONFIG_BLK_DEV_INITRD=y
 CONFIG_EXPERT=y
+# CONFIG_SYSFS_SYSCALL is not set
 CONFIG_BPF_SYSCALL=y
 CONFIG_SOC_SIFIVE=y
 CONFIG_SOC_VIRT=y
 CONFIG_SMP=y
 CONFIG_HOTPLUG_CPU=y
+CONFIG_CPU_IDLE=y
 CONFIG_JUMP_LABEL=y
 CONFIG_MODULES=y
 CONFIG_MODULE_UNLOAD=y
@@ -65,10 +67,9 @@ CONFIG_HW_RANDOM=y
 CONFIG_HW_RANDOM_VIRTIO=y
 CONFIG_SPI=y
 CONFIG_SPI_SIFIVE=y
+# CONFIG_PTP_1588_CLOCK is not set
 CONFIG_GPIOLIB=y
 CONFIG_GPIO_SIFIVE=y
-# CONFIG_PTP_1588_CLOCK is not set
-CONFIG_POWER_RESET=y
 CONFIG_DRM=y
 CONFIG_DRM_RADEON=y
 CONFIG_DRM_VIRTIO_GPU=y
@@ -132,5 +133,3 @@ CONFIG_DEBUG_BLOCK_EXT_DEVT=y
 # CONFIG_FTRACE is not set
 # CONFIG_RUNTIME_TESTING_MENU is not set
 CONFIG_MEMTEST=y
-# CONFIG_SYSFS_SYSCALL is not set
-CONFIG_EFI=y
diff --git a/arch/riscv/configs/rv32_defconfig b/arch/riscv/configs/rv32_defconfig
index 8dd02b842fef..332e43a4a2c3 100644
--- a/arch/riscv/configs/rv32_defconfig
+++ b/arch/riscv/configs/rv32_defconfig
@@ -13,12 +13,14 @@ CONFIG_USER_NS=y
 CONFIG_CHECKPOINT_RESTORE=y
 CONFIG_BLK_DEV_INITRD=y
 CONFIG_EXPERT=y
+# CONFIG_SYSFS_SYSCALL is not set
 CONFIG_BPF_SYSCALL=y
 CONFIG_SOC_SIFIVE=y
 CONFIG_SOC_VIRT=y
 CONFIG_ARCH_RV32I=y
 CONFIG_SMP=y
 CONFIG_HOTPLUG_CPU=y
+CONFIG_CPU_IDLE=y
 CONFIG_JUMP_LABEL=y
 CONFIG_MODULES=y
 CONFIG_MODULE_UNLOAD=y
@@ -67,7 +69,6 @@ CONFIG_HW_RANDOM_VIRTIO=y
 CONFIG_SPI=y
 CONFIG_SPI_SIFIVE=y
 # CONFIG_PTP_1588_CLOCK is not set
-CONFIG_POWER_RESET=y
 CONFIG_DRM=y
 CONFIG_DRM_RADEON=y
 CONFIG_DRM_VIRTIO_GPU=y
@@ -131,4 +132,3 @@ CONFIG_DEBUG_BLOCK_EXT_DEVT=y
 # CONFIG_FTRACE is not set
 # CONFIG_RUNTIME_TESTING_MENU is not set
 CONFIG_MEMTEST=y
-# CONFIG_SYSFS_SYSCALL is not set
diff --git a/arch/riscv/include/asm/cpuidle.h b/arch/riscv/include/asm/cpuidle.h
new file mode 100644
index 000000000000..1042d790e446
--- /dev/null
+++ b/arch/riscv/include/asm/cpuidle.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2021 Allwinner Ltd
+ * Copyright (C) 2021 Western Digital Corporation or its affiliates.
+ */
+
+#ifndef _ASM_RISCV_CPUIDLE_H
+#define _ASM_RISCV_CPUIDLE_H
+
+#include <asm/barrier.h>
+#include <asm/processor.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 dd5f985b1f40..b5b51fd26624 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();
 	raw_local_irq_enable();
 }
 
-- 
2.25.1