From 3af0ada7dd98c6da35c1fd7f107af3b9aa5e904c Mon Sep 17 00:00:00 2001
From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
Date: Thu, 30 Jul 2020 11:02:55 +0530
Subject: [PATCH] cpuidle: pseries: Set the latency-hint before entering CEDE

References: jsc#SLE-13614 bsc#1176914 ltc#186394
Patch-mainline: v5.9-rc1
Git-commit: 3af0ada7dd98c6da35c1fd7f107af3b9aa5e904c

As per the PAPR, each H_CEDE call is associated with a latency-hint to
be passed in the VPA field "cede_latency_hint". The CEDE states that
we were implicitly entering so far is CEDE with latency-hint = 0.

This patch explicitly sets the latency hint corresponding to the CEDE
state that we are currently entering. While at it, we save the
previous hint, to be restored once we wakeup from CEDE. This will be
required in the future when we expose extended-cede states through the
cpuidle framework, where each of them will have a different
cede-latency hint.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
[mpe: Make cede_latency_hint static]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1596087177-30329-2-git-send-email-ego@linux.vnet.ibm.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 drivers/cpuidle/cpuidle-pseries.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c
index 3e058ad2bb51..31c8e51162b2 100644
--- a/drivers/cpuidle/cpuidle-pseries.c
+++ b/drivers/cpuidle/cpuidle-pseries.c
@@ -86,19 +86,27 @@ static void check_and_cede_processor(void)
 	}
 }
 
+#define NR_DEDICATED_STATES	2 /* snooze, CEDE */
+
+static u8 cede_latency_hint[NR_DEDICATED_STATES];
+
 static int dedicated_cede_loop(struct cpuidle_device *dev,
 				struct cpuidle_driver *drv,
 				int index)
 {
+	u8 old_latency_hint;
 
 	pseries_idle_prolog();
 	get_lppaca()->donate_dedicated_cpu = 1;
+	old_latency_hint = get_lppaca()->cede_latency_hint;
+	get_lppaca()->cede_latency_hint = cede_latency_hint[index];
 
 	HMT_medium();
 	check_and_cede_processor();
 
 	local_irq_disable();
 	get_lppaca()->donate_dedicated_cpu = 0;
+	get_lppaca()->cede_latency_hint = old_latency_hint;
 
 	pseries_idle_epilog();
 
@@ -130,7 +138,7 @@ static int shared_cede_loop(struct cpuidle_device *dev,
 /*
  * States for dedicated partition case.
  */
-static struct cpuidle_state dedicated_states[] = {
+static struct cpuidle_state dedicated_states[NR_DEDICATED_STATES] = {
 	{ /* Snooze */
 		.name = "snooze",
 		.desc = "snooze",
@@ -233,7 +241,7 @@ static int pseries_idle_probe(void)
 			max_idle_state = ARRAY_SIZE(shared_states);
 		} else {
 			cpuidle_state_table = dedicated_states;
-			max_idle_state = ARRAY_SIZE(dedicated_states);
+			max_idle_state = NR_DEDICATED_STATES;
 		}
 	} else
 		return -ENODEV;
-- 
2.28.0