MIPS: SMP: Implement parallel CPU bring up for EyeQ

Added support for starting CPUs in parallel on EyeQ to speed up boot time.

On EyeQ5, booting 8 CPUs is now ~90ms faster.
On EyeQ6, booting 32 CPUs is now ~650ms faster.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/Kconfig

@@ -617,6 +617,7 @@ config EYEQ
 	select USB_UHCI_BIG_ENDIAN_DESC if CPU_BIG_ENDIAN
 	select USB_UHCI_BIG_ENDIAN_MMIO if CPU_BIG_ENDIAN
 	select USE_OF
+	select HOTPLUG_PARALLEL if SMP
 	help
 	  Select this to build a kernel supporting EyeQ SoC from Mobileye.
 
@@ -2287,6 +2288,7 @@ config MIPS_CPS
 	select MIPS_CM
 	select MIPS_CPS_PM if HOTPLUG_CPU
 	select SMP
+	select HOTPLUG_SMT if HOTPLUG_PARALLEL
 	select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
 	select SYNC_R4K if (CEVT_R4K || CSRC_R4K)
 	select SYS_SUPPORTS_HOTPLUG_CPU

arch/mips/include/asm/topology.h

@@ -16,6 +16,9 @@
 #define topology_core_id(cpu)			(cpu_core(&cpu_data[cpu]))
 #define topology_core_cpumask(cpu)		(&cpu_core_map[cpu])
 #define topology_sibling_cpumask(cpu)		(&cpu_sibling_map[cpu])
+
+extern struct cpumask __cpu_primary_thread_mask;
+#define cpu_primary_thread_mask ((const struct cpumask *)&__cpu_primary_thread_mask)
 #endif
 
 #endif /* __ASM_TOPOLOGY_H */

arch/mips/kernel/smp-cps.c

@@ -236,6 +236,7 @@ static void __init cps_smp_setup(void)
 			/* Use the number of VPEs in cluster 0 core 0 for smp_num_siblings */
 			if (!cl && !c)
 				smp_num_siblings = core_vpes;
+			cpumask_set_cpu(nvpes, &__cpu_primary_thread_mask);
 
 			for (v = 0; v < min_t(int, core_vpes, NR_CPUS - nvpes); v++) {
 				cpu_set_cluster(&cpu_data[nvpes + v], cl);
@@ -364,6 +365,7 @@ static void __init cps_prepare_cpus(unsigned int max_cpus)
 	cl = cpu_cluster(&current_cpu_data);
 	c = cpu_core(&current_cpu_data);
 	cluster_bootcfg = &mips_cps_cluster_bootcfg[cl];
+	cpu_smt_set_num_threads(core_vpes, core_vpes);
 	core_bootcfg = &cluster_bootcfg->core_config[c];
 	bitmap_set(cluster_bootcfg->core_power, cpu_core(&current_cpu_data), 1);
 	atomic_set(&core_bootcfg->vpe_mask, 1 << cpu_vpe_id(&current_cpu_data));

arch/mips/kernel/smp.c

@@ -56,8 +56,10 @@ EXPORT_SYMBOL(cpu_sibling_map);
 cpumask_t cpu_core_map[NR_CPUS] __read_mostly;
 EXPORT_SYMBOL(cpu_core_map);
 
+#ifndef CONFIG_HOTPLUG_PARALLEL
 static DECLARE_COMPLETION(cpu_starting);
 static DECLARE_COMPLETION(cpu_running);
+#endif
 
 /*
  * A logical cpu mask containing only one VPE per core to
@@ -74,6 +76,8 @@ static cpumask_t cpu_core_setup_map;
 
 cpumask_t cpu_coherent_mask;
 
+struct cpumask __cpu_primary_thread_mask __read_mostly;
+
 unsigned int smp_max_threads __initdata = UINT_MAX;
 
 static int __init early_nosmt(char *s)
@@ -374,10 +378,15 @@ asmlinkage void start_secondary(void)
 	set_cpu_core_map(cpu);
 
 	cpumask_set_cpu(cpu, &cpu_coherent_mask);
+#ifdef CONFIG_HOTPLUG_PARALLEL
+	cpuhp_ap_sync_alive();
+#endif
 	notify_cpu_starting(cpu);
 
+#ifndef CONFIG_HOTPLUG_PARALLEL
 	/* Notify boot CPU that we're starting & ready to sync counters */
 	complete(&cpu_starting);
+#endif
 
 	synchronise_count_slave(cpu);
 
@@ -386,11 +395,13 @@ asmlinkage void start_secondary(void)
 
 	calculate_cpu_foreign_map();
 
+#ifndef CONFIG_HOTPLUG_PARALLEL
 	/*
 	 * Notify boot CPU that we're up & online and it can safely return
 	 * from __cpu_up
 	 */
 	complete(&cpu_running);
+#endif
 
 	/*
 	 * irq will be enabled in ->smp_finish(), enabling it too early
@@ -447,6 +458,12 @@ void __init smp_prepare_boot_cpu(void)
 	set_cpu_online(0, true);
 }
 
+#ifdef CONFIG_HOTPLUG_PARALLEL
+int arch_cpuhp_kick_ap_alive(unsigned int cpu, struct task_struct *tidle)
+{
+	return mp_ops->boot_secondary(cpu, tidle);
+}
+#else
 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 {
 	int err;
@@ -466,6 +483,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 	wait_for_completion(&cpu_running);
 	return 0;
 }
+#endif
 
 #ifdef CONFIG_PROFILING
 /* Not really SMP stuff ... */