[PATCH 15/39] LoongArch: Switch over to GENERIC_CPU_DEVICES

Russell King
2023-10-24T15:19:21Z

Now that GENERIC_CPU_DEVICES calls arch_register_cpu(), which can be
overridden by the arch code, switch over to this to allow common code
to choose when the register_cpu() call is made.

This allows topology_init() to be removed.

This is an intermediate step to the logic being moved to drivers/acpi,
where GENERIC_CPU_DEVICES will do the work when booting with acpi=off.

This is a subtle change. Originally:
- on boot, topology_init() would have marked present CPUs that
io_master() is true for as hotplug-incapable.
- if a CPU is hotplugged that is an io_master(), it can later be
hot-unplugged.

The new behaviour is that any CPU that io_master() is true for will
now always be marked as hotplug-incapable, thus even if it was
hotplugged, it can no longer be hot-unplugged.

This patch also has the effect of moving the registration of CPUs from
subsys to driver core initialisation, prior to any initcalls running.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
Changes since RFC v2:
* Explain the change in behaviour in the patch description
(highlighted by Jonathan Cameron - thanks.) Add note about
initialisation order change.
---
arch/loongarch/Kconfig | 1 +
arch/loongarch/kernel/topology.c | 29 ++---------------------------
2 files changed, 3 insertions(+), 27 deletions(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 2bddd202470e..5bed51adc68c 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -72,6 +72,7 @@ config LOONGARCH
select GENERIC_CLOCKEVENTS
select GENERIC_CMOS_UPDATE
select GENERIC_CPU_AUTOPROBE
+ select GENERIC_CPU_DEVICES
select GENERIC_ENTRY
select GENERIC_GETTIMEOFDAY
select GENERIC_IOREMAP if !ARCH_IOREMAP
diff --git a/arch/loongarch/kernel/topology.c b/arch/loongarch/kernel/topology.c
index 3fd166006698..bf58351beac1 100644
--- a/arch/loongarch/kernel/topology.c
+++ b/arch/loongarch/kernel/topology.c
@@ -10,20 +10,13 @@

#include <acpi/processor.h>

-static DEFINE_PER_CPU(struct cpu, cpu_devices);
-
#ifdef CONFIG_HOTPLUG_CPU
int arch_register_cpu(int cpu)
{
- int ret;
struct cpu *c = &per_cpu(cpu_devices, cpu);

- c->hotpluggable = 1;
- ret = register_cpu(c, cpu);
- if (ret < 0)
- pr_warn("register_cpu %d failed (%d)\n", cpu, ret);
-
- return ret;
+ c->hotpluggable = !io_master(cpu);
+ return register_cpu(c, cpu);
}
EXPORT_SYMBOL(arch_register_cpu);

@@ -36,21 +29,3 @@ void arch_unregister_cpu(int cpu)
}
EXPORT_SYMBOL(arch_unregister_cpu);
#endif
-
-static int __init topology_init(void)
-{
- int i, ret;
-
- for_each_present_cpu(i) {
- struct cpu *c = &per_cpu(cpu_devices, i);
-
- c->hotpluggable = !io_master(i);
- ret = register_cpu(c, i);
- if (ret < 0)
- pr_warn("topology_init: register_cpu %d failed (%d)\n", i, ret);
- }
-
- return 0;
-}
-
-subsys_initcall(topology_init);
--
2.30.2