[PATCH 12/13] powerpc/perf: Thread imc cpuhotplug support

[Madhavan Srinivasan]

From: Anju T Sudhakar <anju at linux.vnet.ibm.com>

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.

Cc: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
Cc: Balbir Singh <bsingharora at gmail.com>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Anton Blanchard <anton at samba.org>
Cc: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
Cc: Michael Neuling <mikey at neuling.org>
Cc: Stewart Smith <stewart at linux.vnet.ibm.com>
Cc: Daniel Axtens <dja at axtens.net>
Cc: Stephane Eranian <eranian at google.com>
Signed-off-by: Anju T Sudhakar <anju at linux.vnet.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>
---
 arch/powerpc/perf/imc-pmu.c | 33 ++++++++++++++++++++++++++++-----
 include/linux/cpuhotplug.h  |  1 +
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
index 6802960db51c..2ff39fe2a5ce 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -687,6 +687,16 @@ 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
@@ -694,20 +704,33 @@ 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();
 
 	per_cpu_add[cpu_id] = (u64)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 						    0);
-	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);
 }
 
 static void thread_imc_ldbar_disable(void *dummy)
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index abde85d9511a..724df46b2c3c 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -138,6 +138,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_ARM_L2X0_ONLINE,
 	CPUHP_AP_PERF_POWERPC_NEST_ONLINE,
 	CPUHP_AP_PERF_POWERPC_COREIMC_ONLINE,
+	CPUHP_AP_PERF_POWERPC_THREADIMC_ONLINE,
 	CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
 	CPUHP_AP_WORKQUEUE_ONLINE,
 	CPUHP_AP_RCUTREE_ONLINE,
-- 
2.7.4