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Subject[PATCH v2 08/12] clocksource: mips-gic-timer: Enable counter when CPUs start
Date
From: Paul Burton <paulburton@kernel.org>

In multi-cluster MIPS I6500 systems we have a GIC in each cluster, each
with its own counter. When a cluster powers up the counter will be
stopped, with the COUNTSTOP bit set in the GIC_CONFIG register.

In single cluster systems it has been fine for us to clear COUNTSTOP
once in gic_clocksource_of_init() in order to start the counter, since
with only one cluster we know that we won't be resetting that cluster's
GIC at any point (ignoring suspend/resume cycles which would need to
handle clearing COUNTSTOP in the resume path). Once we support
multi-cluster systems this will only have started the counter in the
boot cluster, and any CPUs in other clusters will find their counter
stopped which will break the GIC clock_event_device.

Resolve this by having CPUs clear the COUNTSTOP bit when they come
online, using the existing gic_starting_cpu() CPU hotplug callback. This
will allow CPUs in secondary clusters to ensure that the cluster's GIC
counter is running as expected.

Signed-off-by: Paul Burton <paulburton@kernel.org>
Signed-off-by: Chao-ying Fu <cfu@wavecomp.com>
Signed-off-by: Dragan Mladjenovic <dragan.mladjenovic@syrmia.com>

diff --git a/drivers/clocksource/mips-gic-timer.c b/drivers/clocksource/mips-gic-timer.c
index 6632d314a2c0..90a736a13115 100644
--- a/drivers/clocksource/mips-gic-timer.c
+++ b/drivers/clocksource/mips-gic-timer.c
@@ -119,6 +119,9 @@ static void gic_update_frequency(void *data)

static int gic_starting_cpu(unsigned int cpu)
{
+ /* Ensure the GIC counter is running */
+ clear_gic_config(GIC_CONFIG_COUNTSTOP);
+
gic_clockevent_cpu_init(cpu, this_cpu_ptr(&gic_clockevent_device));
return 0;
}
@@ -289,9 +292,6 @@ static int __init gic_clocksource_of_init(struct device_node *node)
pr_warn("Unable to register clock notifier\n");
}

- /* And finally start the counter */
- clear_gic_config(GIC_CONFIG_COUNTSTOP);
-
/*
* It's safe to use the MIPS GIC timer as a sched clock source only if
* its ticks are stable, which is true on either the platforms with
--
2.17.1
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