linux-kernel - [PATCH 04/25] clocksource/drivers/exynos_mct: Increase priority over ARM arch timer

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Message-Id: <20190626144651.16742-4-daniel.lezcano@linaro.org>
Date:   Wed, 26 Jun 2019 16:46:30 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     tglx@...utronix.de
Cc:     linux-kernel@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Will Deacon <will.deacon@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Borislav Petkov <bp@...e.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        "Kulkarni, Ganapatrao" <Ganapatrao.Kulkarni@...ium.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Guo Ren <ren_guo@...ky.com>, Joseph Lo <josephl@...dia.com>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Hoan Tran <Hoan@...amperecomputing.com>,
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM/SAMSUNG EXYNOS
        ARM ARCHITECTURES),
        linux-samsung-soc@...r.kernel.org (moderated list:ARM/SAMSUNG EXYNOS
        ARM ARCHITECTURES)
Subject: [PATCH 04/25] clocksource/drivers/exynos_mct: Increase priority over ARM arch timer

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

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>
---
 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 34bd250d46c6..6aa10cbc1d59 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -209,7 +209,7 @@ 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,
@@ -464,7 +464,7 @@ 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 5c6062206760..87c211adf49e 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_TEGRA_TIMER_STARTING,
-- 
2.17.1