linux-kernel - [RFC 3/3] Introduce capability for firmware-enabled-stop

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Date:   Wed,  4 Mar 2020 21:31:23 +0530
From:   Pratik Rajesh Sampat <psampat@...ux.ibm.com>
To:     linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
        mpe@...erman.id.au, mikey@...ling.org, npiggin@...il.com,
        vaidy@...ux.ibm.com, ego@...ux.vnet.ibm.com,
        skiboot@...ts.ozlabs.org, oohall@...il.com, psampat@...ux.ibm.com,
        pratik.r.sampat@...il.com
Subject: [RFC 3/3] Introduce capability for firmware-enabled-stop

Design patch that introduces the capability for firmware to handle the
stop states instead. A bit is set based on the discovery of the feature
and correspondingly also the responsibility to handle the stop states.

The commit does not contain calling into the firmware to utilize
firmware enabled stop.

Signed-off-by: Pratik Rajesh Sampat <psampat at linux.ibm.com>
---
 arch/powerpc/include/asm/processor.h | 1 +
 arch/powerpc/kernel/dt_cpu_ftrs.c    | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index 277dbabafd02..978fab35d133 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -430,6 +430,7 @@ extern unsigned long cpuidle_disable;
 enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF};
 
 #define STOP_ENABLE		0x00000001
+#define FIRMWARE_STOP_ENABLE	0x00000010
 
 #define STOP_VERSION_P9       0x1
 #define STOP_VERSION_P9_V1    0x2
diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
index 63e30aa49356..e00f8afabc46 100644
--- a/arch/powerpc/kernel/dt_cpu_ftrs.c
+++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
@@ -313,6 +313,14 @@ static int __init feat_enable_idle_stop_quirk(struct dt_cpu_feature *f)
 
 	return 1;
 }
+
+static int __init feat_enable_firmware_stop(struct dt_cpu_feature *f)
+{
+	stop_dep.cpuidle_prop |= FIRMWARE_STOP_ENABLE;
+
+	return 1;
+}
+
 static int __init feat_enable_mmu_hash(struct dt_cpu_feature *f)
 {
 	u64 lpcr;
@@ -608,6 +616,7 @@ static struct dt_cpu_feature_match __initdata
 	{"alignment-interrupt-dsisr", feat_enable_align_dsisr, 0},
 	{"idle-stop", feat_enable_idle_stop, 0},
 	{"idle-stop-v1", feat_enable_idle_stop_quirk, 0},
+	{"firmware-stop-supported", feat_enable_firmware_stop, 0},
 	{"machine-check-power8", feat_enable_mce_power8, 0},
 	{"performance-monitor-power8", feat_enable_pmu_power8, 0},
 	{"data-stream-control-register", feat_enable_dscr, CPU_FTR_DSCR},
-- 
2.24.1