cpu/x86/mp_init.c: Use linked list data structures

There is no need to keep track of device structures separately.

Change-Id: Ie728110fc8c60fec94ae4bedf74e17740cf78f67
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64340
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <inforichland@gmail.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
diff --git a/src/cpu/x86/mp_init.c b/src/cpu/x86/mp_init.c
index dd9deda..e3b294f 100644
--- a/src/cpu/x86/mp_init.c
+++ b/src/cpu/x86/mp_init.c
@@ -107,7 +107,7 @@
 /* The sipi vector rmodule is included in the ramstage using 'objdump -B'. */
 extern char _binary_sipi_vector_start[];
 
-/* The SIPI vector is loaded at the SMM_DEFAULT_BASE. The reason is at the
+/* The SIPI vector is loaded at the SMM_DEFAULT_BASE. The reason is that the
  * memory range is already reserved so the OS cannot use it. That region is
  * free to use for AP bringup before SMM is initialized. */
 static const uintptr_t sipi_vector_location = SMM_DEFAULT_BASE;
@@ -121,9 +121,6 @@
 static int global_num_aps;
 static struct mp_flight_plan mp_info;
 
-/* Keep track of device structure for each CPU. */
-static struct device *cpus_dev[CONFIG_MAX_CPUS];
-
 static inline void barrier_wait(atomic_t *b)
 {
 	while (atomic_read(b) == 0)
@@ -175,6 +172,8 @@
 	stop_this_cpu();
 }
 
+static struct bus *g_cpu_bus;
+
 /* By the time APs call ap_init() caching has been setup, and microcode has
  * been loaded. */
 static void asmlinkage ap_init(void)
@@ -185,7 +184,11 @@
 	enable_lapic();
 	setup_lapic_interrupts();
 
-	info->cpu = cpus_dev[info->index];
+	struct device *dev = g_cpu_bus->children;
+	for (unsigned int i = info->index; i > 0; i--)
+		dev = dev->sibling;
+
+	info->cpu = dev;
 
 	cpu_add_map_entry(info->index);
 
@@ -384,7 +387,6 @@
 			continue;
 		}
 		new->name = processor_name;
-		cpus_dev[i] = new;
 	}
 
 	return max_cpus;
@@ -579,6 +581,8 @@
 	int num_cpus;
 	atomic_t *ap_count;
 
+	g_cpu_bus = cpu_bus;
+
 	init_bsp(cpu_bus);
 
 	if (p == NULL || p->flight_plan == NULL || p->num_records < 1) {