[PATCH v11 10/10] powerpc/perf: Thread imc cpuhotplug support

[Anju T Sudhakar]

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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
---
 arch/powerpc/perf/imc-pmu.c | 38 +++++++++++++++++++++++++++++++++++++-
 include/linux/cpuhotplug.h  |  1 +
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
index 3deefb1..afd5306 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -346,6 +346,37 @@ static int imc_mem_init(struct imc_pmu *pmu_ptr)
 	return 0;
 }
 
+static int ppc_thread_imc_cpu_online(unsigned int cpu)
+{
+	int rc = 0;
+	u64 ldbar_value;
+
+	if (per_cpu(thread_imc_mem, cpu) == NULL)
+		rc = thread_imc_mem_alloc(cpu, thread_imc_mem_size);
+
+	if (rc)
+		mtspr(SPRN_LDBAR, 0);
+
+	ldbar_value = ((u64)per_cpu(thread_imc_mem, cpu) & (u64)THREAD_IMC_LDBAR_MASK) |
+							(u64)THREAD_IMC_ENABLE;
+	mtspr(SPRN_LDBAR, ldbar_value);
+	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;
@@ -901,6 +932,9 @@ int 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 */
 	}
@@ -942,7 +976,9 @@ int init_imc_pmu(struct imc_events *events, int idx,
 		cpuhp_remove_state(CPUHP_AP_PERF_POWERPC_CORE_IMC_ONLINE);
 	}
 	/* For thread_imc, we have allocated memory, we need to free it */
-	if (pmu_ptr->domain == IMC_DOMAIN_THREAD)
+	if (pmu_ptr->domain == IMC_DOMAIN_THREAD) {
 		cleanup_all_thread_imc_memory();
+		cpuhp_remove_state(CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE);
+	}
 	return ret;
 }
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