[PATCH v9 10/10] powerpc/perf: Thread imc cpuhotplug support

[Anju T Sudhakar <anju@linux.vnet.ibm.com>]

Code to add support for thread IMC on cpuhotplug.

When a cpu goes offline, the LDBAR for that cpu is disabled, and when it comes
back online the previous ldbar value is written back to the LDBAR for that cpu.

To register the hotplug functions for thread_imc, a new state
CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE is added to the list of existing
states.

Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
---
 arch/powerpc/perf/imc-pmu.c | 35 +++++++++++++++++++++++++++++++++--
 include/linux/cpuhotplug.h  |  1 +
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
index 13ff6dc..ee582b0 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -396,14 +396,22 @@ bool is_core_imc_mem_inited(int cpu)
  */
 static void thread_imc_mem_alloc(int cpu_id)
 {
-	u64 ldbar_addr, ldbar_value;
 	int phys_id = topology_physical_package_id(cpu_id);
 
 	per_cpu_add[cpu_id] = (u64)alloc_pages_exact_nid(phys_id,
 			(size_t)IMC_THREAD_COUNTER_MEM, GFP_KERNEL | __GFP_ZERO);
+}
+
+static void thread_imc_update_ldbar(unsigned int cpu_id)
+{
+	u64 ldbar_addr, ldbar_value;
+
+	if (per_cpu_add[cpu_id] == 0)
+		thread_imc_mem_alloc(cpu_id);
+
 	ldbar_addr = (u64)virt_to_phys((void *)per_cpu_add[cpu_id]);
 	ldbar_value = (ldbar_addr & (u64)THREAD_IMC_LDBAR_MASK) |
-		(u64)THREAD_IMC_ENABLE;
+			(u64)THREAD_IMC_ENABLE;
 	mtspr(SPRN_LDBAR, ldbar_value);
 }
 
@@ -442,6 +450,26 @@ static void core_imc_change_cpu_context(int old_cpu, int new_cpu)
 	perf_pmu_migrate_context(&core_imc_pmu->pmu, old_cpu, new_cpu);
 }
 
+static int ppc_thread_imc_cpu_online(unsigned int cpu)
+{
+	thread_imc_update_ldbar(cpu);
+	return 0;
+}
+
+static int ppc_thread_imc_cpu_offline(unsigned int cpu)
+{
+	mtspr(SPRN_LDBAR, 0);
+	return 0;
+}
+
+void thread_imc_cpu_init(void)
+{
+	cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE,
+			  "perf/powerpc/imc_thread:online",
+			  ppc_thread_imc_cpu_online,
+			  ppc_thread_imc_cpu_offline);
+}
+
 static int ppc_core_imc_cpu_online(unsigned int cpu)
 {
 	const struct cpumask *l_cpumask;
@@ -953,6 +981,9 @@ int __init init_imc_pmu(struct imc_events *events, int idx,
 		if (ret)
 			return ret;
 		break;
+	case IMC_DOMAIN_THREAD:
+		thread_imc_cpu_init();
+		break;
 	default:
 		return -1;  /* Unknown domain */
 	}
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index e145fff..937d1ec 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -141,6 +141,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_ARM_QCOM_L3_ONLINE,
 	CPUHP_AP_PERF_POWERPC_NEST_IMC_ONLINE,
 	CPUHP_AP_PERF_POWERPC_CORE_IMC_ONLINE,
+	CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE,
 	CPUHP_AP_WORKQUEUE_ONLINE,
 	CPUHP_AP_RCUTREE_ONLINE,
 	CPUHP_AP_ONLINE_DYN,
-- 
2.7.4