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

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Date:   Mon, 21 Nov 2022 12:56:47 -0800
From:   Palmer Dabbelt <palmer@...osinc.com>
To:     Conor Dooley <conor@...nel.org>
Cc:     anup@...infault.org, rafael@...nel.org, daniel.lezcano@...aro.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>, aou@...s.berkeley.edu,
        linux-pm@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux@...osinc.com,
        Palmer Dabbelt <palmer@...osinc.com>
Subject: [PATCH] cpuidle: riscv-sbi: Stop using non-retentive suspend

From: Palmer Dabbelt <palmer@...osinc.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@...osinc.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