[PATCH] cpuidle: riscv-sbi: Stop using non-retentive suspend

Palmer Dabbelt
2022-11-21T20:57:30Z

From: Palmer Dabbelt <palmer@rivosinc.com>

As per [1], whether or not the core can wake up from non-retentive
suspend is a platform-specific detail. We don't have any way to encode
that, so just stop using them until we've sorted that out.

Link: https://github.com/riscv-non-isa/riscv-sbi-doc/issues/98#issuecomment-1288564687
Fixes: 6abf32f1d9c5 ("cpuidle: Add RISC-V SBI CPU idle driver")
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

---

This should allow us to revert 232ccac1bd9b ("clocksource/drivers/riscv:
Events are stopped during CPU suspend"), which fixes suspend on the D1
but breaks timers everywhere.
---
drivers/cpuidle/cpuidle-riscv-sbi.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/drivers/cpuidle/cpuidle-riscv-sbi.c b/drivers/cpuidle/cpuidle-riscv-sbi.c
index 05fe2902df9a..9d1063a54495 100644
--- a/drivers/cpuidle/cpuidle-riscv-sbi.c
+++ b/drivers/cpuidle/cpuidle-riscv-sbi.c
@@ -214,6 +214,17 @@ static bool sbi_suspend_state_is_valid(u32 state)
if (state > SBI_HSM_SUSPEND_NON_RET_DEFAULT &&
state < SBI_HSM_SUSPEND_NON_RET_PLATFORM)
return false;
+
+ /*
+ * Whether or not RISC-V systems deliver interrupts to harts in a
+ * non-retentive suspend state is a platform-specific detail. This can
+ * leave the hart unable to wake up, so just mark these states as
+ * unsupported until we have a mechanism to expose these
+ * platform-specific details to Linux.
+ */
+ if (state & SBI_HSM_SUSP_NON_RET_BIT)
+ return false;
+
return true;
}

--
2.38.1