clocksource: mips-gic-timer: Enable counter when CPUs start

In multi-cluster MIPS I6500 systems there is 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 to clear COUNTSTOP once
in gic_clocksource_of_init() to start the counter. In 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>
Signed-off-by: Aleksandar Rikalo <arikalo@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Serge Semin <fancer.lancer@gmail.com>
Tested-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

diff --git a/drivers/clocksource/mips-gic-timer.c b/drivers/clocksource/mips-gic-timer.c
index 7907b740497a5c8d1c8f07a458fcda8bcb868ba6..abb685a080a5bbe09a2b5a01e8293b68fb636831 100644 (file)
--- a/drivers/clocksource/mips-gic-timer.c
+++ b/drivers/clocksource/mips-gic-timer.c
@@ -115,6 +115,9 @@ 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;
 }
@@ -288,9 +291,6 @@ 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