linux-kernel - [PATCH v2] clocksource: exynos_mct: Increase priority over ARM arch timer

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Date:   Thu, 21 Mar 2019 09:26:08 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: [PATCH v2] clocksource: exynos_mct: Increase priority over ARM arch
 timer

Exynos Multi-Core Timer driver (exynos_mct) must be 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. Increase MCT timer rating
and hotplug priority over ARM Archictected timer driver to achieve that.

Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
Reviewed-by: Krzysztof Kozlowski <krzk@...nel.org>
---
v2: added comments about the relation to ARM arch timer
    rebased onto v5.1-rc1
v1: https://patchwork.kernel.org/patch/10814921/
---
 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 e78281d07b70..53fb48de9589 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -115,10 +115,10 @@ 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