[PATCH v8 10/10] powerpc/perf: Thread imc cpuhotplug support

[Anju T Sudhakar]

This patch adds 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_THREADIMC_ONLINE is added to the list of existing
states.

Reviewed-by: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Anju T Sudhakar <anju@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
---
 arch/powerpc/perf/imc-pmu.c | 32 +++++++++++++++++++++++++++-----
 include/linux/cpuhotplug.h  |  1 +
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
index cfd112e..f10489f 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -982,6 +982,16 @@ static void cleanup_all_thread_imc_memory(void)
 	on_each_cpu(cleanup_thread_imc_memory, NULL, 1);
 }
 
+static void thread_imc_update_ldbar(unsigned int cpu_id)
+{
+	u64 ldbar_addr, ldbar_value;
+
+	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;
+	mtspr(SPRN_LDBAR, ldbar_value);
+}
+
 /*
  * Allocates a page of memory for each of the online cpus, and, writes the
  * physical base address of that page to the LDBAR for that cpu. This starts
@@ -989,21 +999,33 @@ static void cleanup_all_thread_imc_memory(void)
  */
 static void thread_imc_mem_alloc(void *dummy)
 {
-	u64 ldbar_addr, ldbar_value;
 	int cpu_id = smp_processor_id();
 	int phys_id = topology_physical_package_id(smp_processor_id());
 
 	per_cpu_add[cpu_id] = (u64)alloc_pages_exact_nid(phys_id,
 			(size_t)IMC_THREAD_COUNTER_MEM, GFP_KERNEL | __GFP_ZERO);
-	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;
-	mtspr(SPRN_LDBAR, ldbar_value);
+	thread_imc_update_ldbar(cpu_id);
+}
+
+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)
 {
 	on_each_cpu(thread_imc_mem_alloc, NULL, 1);
+	cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_THREADIMC_ONLINE,
+				"POWER_THREAD_IMC_ONLINE",
+				ppc_thread_imc_cpu_online,
+				ppc_thread_imc_cpu_offline);
 }
 
 /*
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index e7b7712..bbec927 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -139,6 +139,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
 	CPUHP_AP_PERF_POWERPC_NEST_ONLINE,
 	CPUHP_AP_PERF_POWERPC_COREIMC_ONLINE,
+	CPUHP_AP_PERF_POWERPC_THREADIMC_ONLINE,
 	CPUHP_AP_WORKQUEUE_ONLINE,
 	CPUHP_AP_RCUTREE_ONLINE,
 	CPUHP_AP_ONLINE_DYN,
-- 
2.7.4