[PATCH] riscv: Enable ARCH_SUSPEND_POSSIBLE for s2idle

[Song Shuai]

With this configuration opened, the basic platform-independent s2idle is
provided by the sole "s2idle" string in `/sys/power/mem_sleep`.

At the end of s2idle, harts will hit the `wfi` instruction or enter the
SUSPENDED state through the sbi_cpuidle driver. The interrupt of possible
wakeup devices will be kept to wake the system up.

And platform-specific sleep states can be provided by future ACPI and
SBI SUSP extension support.

Signed-off-by: Song Shuai <songshuaishuai at tinylab.org>
---
 arch/riscv/Kconfig | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 348c0fa1fc8c..4bb818035585 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -805,6 +805,9 @@ config ARCH_HIBERNATION_POSSIBLE
 config ARCH_HIBERNATION_HEADER
 	def_bool HIBERNATION
 
+config ARCH_SUSPEND_POSSIBLE
+	def_bool y
+
 endmenu # "Power management options"
 
 menu "CPU Power Management"
-- 
2.20.1