linux-kernel - [PATCH] arm64: dts: Hi3660: Fix state id for 'CPU

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Message-Id: <1511415614-9859-1-git-send-email-leo.yan@linaro.org>
Date:   Thu, 23 Nov 2017 13:40:14 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Wei Xu <xuwei5@...ilicon.com>, Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org
Cc:     Leo Yan <leo.yan@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: [PATCH] arm64: dts: Hi3660: Fix state id for 'CPU_NAP' state

Thanks a lot for Vincent Guittot careful work to find bug for 'CPU_NAP'
idle state. From ftrace log we can observe CA73 CPUs can be easily waken
up from 'CPU_NAP' state but the 'waken up' CPUs doesn't handle anything
and sleep again; so there have tons of trace events for CA73 CPUs
entering and exiting idle state.

On Hi3660 CA73 has retention state 'CPU_NAP' for CPU idle, this state we
set its psci parameter as '0x0000001' and from this parameter it can
calculate state id is 1. Unfortunately ARM trusted firmware (ARM-TF)
takes 1 as a invalid value for state id, so the CPU cannot enter idle
state and directly bail out to kernel.

This commit changes psci parameter to '0x00000000' for state id = 0;
this id is accepted by ARM trusted firmware and finally CPU can stay
properly in 'CPU_NAP' state.

Cc: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 arch/arm64/boot/dts/hisilicon/hi3660.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/hisilicon/hi3660.dtsi b/arch/arm64/boot/dts/hisilicon/hi3660.dtsi
index ab0b95b..5666d29 100644
--- a/arch/arm64/boot/dts/hisilicon/hi3660.dtsi
+++ b/arch/arm64/boot/dts/hisilicon/hi3660.dtsi
@@ -147,7 +147,7 @@

 			CPU_NAP: cpu-nap {
 				compatible = "arm,idle-state";
-				arm,psci-suspend-param = <0x0000001>;
+				arm,psci-suspend-param = <0x0000000>;
 				entry-latency-us = <7>;
 				exit-latency-us = <2>;
 				min-residency-us = <15>;
-- 
2.7.4