linux-kernel - [PATCH AUTOSEL 4.19 113/158] clocksource/drivers/exynos_mct: Increase priority over ARM arch timer

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Date:   Mon, 15 Jul 2019 10:17:24 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.19 113/158] clocksource/drivers/exynos_mct: Increase priority over ARM arch timer

From: Marek Szyprowski <m.szyprowski@...sung.com>

[ Upstream commit 6282edb72bed5324352522d732080d4c1b9dfed6 ]

Exynos SoCs based on CA7/CA15 have 2 timer interfaces: custom Exynos MCT
(Multi Core Timer) and standard ARM Architected Timers.

There are use cases, where both timer interfaces are used simultanously.
One of such examples is using Exynos MCT for the main system timer and
ARM Architected Timers for the KVM and virtualized guests (KVM requires
arch timers).

Exynos Multi-Core Timer driver (exynos_mct) must be however started
before ARM Architected Timers (arch_timer), because they both share some
common hardware blocks (global system counter) and turning on MCT is
needed to get ARM Architected Timer working properly.

To ensure selecting Exynos MCT as the main system timer, increase MCT
timer rating. To ensure proper starting order of both timers during
suspend/resume cycle, increase MCT hotplug priority over ARM Archictected
Timers.

Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
Reviewed-by: Krzysztof Kozlowski <krzk@...nel.org>
Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/clocksource/exynos_mct.c | 4 ++--
 include/linux/cpuhotplug.h       | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index d55c30f6981d..aaf5bfa9bd9c 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -211,7 +211,7 @@ static void exynos4_frc_resume(struct clocksource *cs)
 
 static struct clocksource mct_frc = {
 	.name		= "mct-frc",
-	.rating		= 400,
+	.rating		= 450,	/* use value higher than ARM arch timer */
 	.read		= exynos4_frc_read,
 	.mask		= CLOCKSOURCE_MASK(32),
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
@@ -466,7 +466,7 @@ static int exynos4_mct_starting_cpu(unsigned int cpu)
 	evt->set_state_oneshot_stopped = set_state_shutdown;
 	evt->tick_resume = set_state_shutdown;
 	evt->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
-	evt->rating = 450;
+	evt->rating = 500;	/* use value higher than ARM arch timer */
 
 	exynos4_mct_write(TICK_BASE_CNT, mevt->base + MCT_L_TCNTB_OFFSET);
 
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index d64d8c2bbdab..6df31106115d 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -116,10 +116,10 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_ARM_ACPI_STARTING,
 	CPUHP_AP_PERF_ARM_STARTING,
 	CPUHP_AP_ARM_L2X0_STARTING,
+	CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING,
 	CPUHP_AP_ARM_ARCH_TIMER_STARTING,
 	CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
 	CPUHP_AP_JCORE_TIMER_STARTING,
-	CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING,
 	CPUHP_AP_ARM_TWD_STARTING,
 	CPUHP_AP_QCOM_TIMER_STARTING,
 	CPUHP_AP_ARMADA_TIMER_STARTING,
-- 
2.20.1