[PATCH v2 1/5] powerpc/smp: Parse ibm,thread-groups with multiple properties

[Gautham R. Shenoy]

From: "Gautham R. Shenoy" <ego@xxxxxxxxxxxxxxxxxx>

The "ibm,thread-groups" device-tree property is an array that is used
to indicate if groups of threads within a core share certain
properties. It provides details of which property is being shared by
which groups of threads. This array can encode information about
multiple properties being shared by different thread-groups within the
core.

Example: Suppose,
"ibm,thread-groups" = [1,2,4,8,10,12,14,9,11,13,15,2,2,4,8,10,12,14,9,11,13,15]

This can be decomposed up into two consecutive arrays:

a) [1,2,4,8,10,12,14,9,11,13,15]
b) [2,2,4,8,10,12,14,9,11,13,15]

where in,

a) provides information of Property "1" being shared by "2" groups,
   each with "4" threads each. The "ibm,ppc-interrupt-server#s" of the
   first group is {8,10,12,14} and the "ibm,ppc-interrupt-server#s" of
   the second group is {9,11,13,15}. Property "1" is indicative of
   the thread in the group sharing L1 cache, translation cache and
   Instruction Data flow.

b) provides information of Property "2" being shared by "2" groups,
   each group with "4" threads. The "ibm,ppc-interrupt-server#s" of
   the first group is {8,10,12,14} and the
   "ibm,ppc-interrupt-server#s" of the second group is
   {9,11,13,15}. Property "2" indicates that the threads in each group
   share the L2-cache.

The existing code assumes that the "ibm,thread-groups" encodes
information about only one property. Hence even on platforms which
encode information about multiple properties being shared by the
corresponding groups of threads, the current code will only pick the
first one. (In the above example, it will only consider
[1,2,4,8,10,12,14,9,11,13,15] but not [2,2,4,8,10,12,14,9,11,13,15]).

This patch extends the parsing support on platforms which encode
information about multiple properties being shared by the
corresponding groups of threads.

Signed-off-by: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>
---
 arch/powerpc/kernel/smp.c | 174 ++++++++++++++++++++++++++++++----------------
 1 file changed, 113 insertions(+), 61 deletions(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 8c2857c..88d88ad 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -106,6 +106,15 @@ struct thread_groups {
 	unsigned int thread_list[MAX_THREAD_LIST_SIZE];
 };
 
+/* Maximum number of properties that groups of threads within a core can share */
+#define MAX_THREAD_GROUP_PROPERTIES 1
+
+struct thread_groups_list {
+	unsigned int nr_properties;
+	struct thread_groups property_tgs[MAX_THREAD_GROUP_PROPERTIES];
+};
+
+static struct thread_groups_list tgl[NR_CPUS] __initdata;
 /*
  * On big-cores system, cpu_l1_cache_map for each CPU corresponds to
  * the set its siblings that share the L1-cache.
@@ -695,81 +704,98 @@ static void or_cpumasks_related(int i, int j, struct cpumask *(*srcmask)(int),
 /*
  * parse_thread_groups: Parses the "ibm,thread-groups" device tree
  *                      property for the CPU device node @dn and stores
- *                      the parsed output in the thread_groups
- *                      structure @tg if the ibm,thread-groups[0]
- *                      matches @property.
+ *                      the parsed output in the thread_groups_list
+ *                      structure @tglp.
  *
  * @dn: The device node of the CPU device.
- * @tg: Pointer to a thread group structure into which the parsed
+ * @tglp: Pointer to a thread group list structure into which the parsed
  *      output of "ibm,thread-groups" is stored.
- * @property: The property of the thread-group that the caller is
- *            interested in.
  *
  * ibm,thread-groups[0..N-1] array defines which group of threads in
  * the CPU-device node can be grouped together based on the property.
  *
- * ibm,thread-groups[0] tells us the property based on which the
+ * This array can represent thread groupings for multiple properties.
+ *
+ * ibm,thread-groups[i + 0] tells us the property based on which the
  * threads are being grouped together. If this value is 1, it implies
  * that the threads in the same group share L1, translation cache.
  *
- * ibm,thread-groups[1] tells us how many such thread groups exist.
+ * ibm,thread-groups[i+1] tells us how many such thread groups exist for the
+ * property ibm,thread-groups[i]
  *
- * ibm,thread-groups[2] tells us the number of threads in each such
+ * ibm,thread-groups[i+2] tells us the number of threads in each such
  * group.
+ * Suppose k = (ibm,thread-groups[i+1] * ibm,thread-groups[i+2]), then,
  *
- * ibm,thread-groups[3..N-1] is the list of threads identified by
+ * ibm,thread-groups[i+3..i+k+2] (is the list of threads identified by
  * "ibm,ppc-interrupt-server#s" arranged as per their membership in
  * the grouping.
  *
- * Example: If ibm,thread-groups = [1,2,4,5,6,7,8,9,10,11,12] it
- * implies that there are 2 groups of 4 threads each, where each group
- * of threads share L1, translation cache.
+ * Example:
+ * If "ibm,thread-groups" = [1,2,4,8,10,12,14,9,11,13,15,2,2,4,8,10,12,14,9,11,13,15]
+ * This can be decomposed up into two consecutive arrays:
+ * a) [1,2,4,8,10,12,14,9,11,13,15]
+ * b) [2,2,4,8,10,12,14,9,11,13,15]
+ *
+ * where in,
+ *
+ * a) provides information of Property "1" being shared by "2" groups,
+ *  each with "4" threads each. The "ibm,ppc-interrupt-server#s" of
+ *  the first group is {8,10,12,14} and the
+ *  "ibm,ppc-interrupt-server#s" of the second group is
+ *  {9,11,13,15}. Property "1" is indicative of the thread in the
+ *  group sharing L1 cache, translation cache and Instruction Data
+ *  flow.
  *
- * The "ibm,ppc-interrupt-server#s" of the first group is {5,6,7,8}
- * and the "ibm,ppc-interrupt-server#s" of the second group is {9, 10,
- * 11, 12} structure
+ * b) provides information of Property "2" being shared by "2" groups,
+ *  each group with "4" threads. The "ibm,ppc-interrupt-server#s" of
+ *  the first group is {8,10,12,14} and the
+ *  "ibm,ppc-interrupt-server#s" of the second group is
+ *  {9,11,13,15}. Property "2" indicates that the threads in each
+ *  group share the L2-cache.
  *
  * Returns 0 on success, -EINVAL if the property does not exist,
  * -ENODATA if property does not have a value, and -EOVERFLOW if the
  * property data isn't large enough.
  */
 static int parse_thread_groups(struct device_node *dn,
-			       struct thread_groups *tg,
-			       unsigned int property)
+			       struct thread_groups_list *tglp)
 {
-	int i;
-	u32 thread_group_array[3 + MAX_THREAD_LIST_SIZE];
-	u32 *thread_list;
+	unsigned int property_idx = 0;
+	u32 *thread_group_array;
 	size_t total_threads;
-	int ret;
+	int ret = 0, count;
+	u32 *thread_list;
+	int i = 0;
 
+	count = of_property_count_u32_elems(dn, "ibm,thread-groups");
+	thread_group_array = kcalloc(count, sizeof(u32), GFP_KERNEL);
 	ret = of_property_read_u32_array(dn, "ibm,thread-groups",
-					 thread_group_array, 3);
+					 thread_group_array, count);
 	if (ret)
-		return ret;
-
-	tg->property = thread_group_array[0];
-	tg->nr_groups = thread_group_array[1];
-	tg->threads_per_group = thread_group_array[2];
-	if (tg->property != property ||
-	    tg->nr_groups < 1 ||
-	    tg->threads_per_group < 1)
-		return -ENODATA;
+		goto out_free;
 
-	total_threads = tg->nr_groups * tg->threads_per_group;
+	while (i < count && property_idx < MAX_THREAD_GROUP_PROPERTIES) {
+		int j;
+		struct thread_groups *tg = &tglp->property_tgs[property_idx++];
 
-	ret = of_property_read_u32_array(dn, "ibm,thread-groups",
-					 thread_group_array,
-					 3 + total_threads);
-	if (ret)
-		return ret;
+		tg->property = thread_group_array[i];
+		tg->nr_groups = thread_group_array[i + 1];
+		tg->threads_per_group = thread_group_array[i + 2];
+		total_threads = tg->nr_groups * tg->threads_per_group;
 
-	thread_list = &thread_group_array[3];
+		thread_list = &thread_group_array[i + 3];
 
-	for (i = 0 ; i < total_threads; i++)
-		tg->thread_list[i] = thread_list[i];
+		for (j = 0; j < total_threads; j++)
+			tg->thread_list[j] = thread_list[j];
+		i = i + 3 + total_threads;
+	}
 
-	return 0;
+	tglp->nr_properties = property_idx;
+
+out_free:
+	kfree(thread_group_array);
+	return ret;
 }
 
 /*
@@ -805,50 +831,76 @@ static int get_cpu_thread_group_start(int cpu, struct thread_groups *tg)
 	return -1;
 }
 
+static struct thread_groups *__init get_thread_groups(int cpu,
+						      int group_property,
+						      int *err)
+{
+	struct device_node *dn = of_get_cpu_node(cpu, NULL);
+	struct thread_groups_list *cpu_tgl = &tgl[cpu];
+	struct thread_groups *tg = NULL;
+	int i;
+	*err = 0;
+
+	if (!dn) {
+		*err = -ENODATA;
+		return NULL;
+	}
+
+	if (!cpu_tgl->nr_properties) {
+		*err = parse_thread_groups(dn, cpu_tgl);
+		if (*err)
+			goto out;
+	}
+
+	for (i = 0; i < cpu_tgl->nr_properties; i++) {
+		if (cpu_tgl->property_tgs[i].property == group_property) {
+			tg = &cpu_tgl->property_tgs[i];
+			break;
+		}
+	}
+
+	if (!tg)
+		*err = -EINVAL;
+out:
+	of_node_put(dn);
+	return tg;
+}
+
 static int init_cpu_l1_cache_map(int cpu)
 
 {
-	struct device_node *dn = of_get_cpu_node(cpu, NULL);
-	struct thread_groups tg = {.property = 0,
-				   .nr_groups = 0,
-				   .threads_per_group = 0};
 	int first_thread = cpu_first_thread_sibling(cpu);
 	int i, cpu_group_start = -1, err = 0;
+	struct thread_groups *tg = NULL;
 
-	if (!dn)
-		return -ENODATA;
-
-	err = parse_thread_groups(dn, &tg, THREAD_GROUP_SHARE_L1);
-	if (err)
-		goto out;
+	tg = get_thread_groups(cpu, THREAD_GROUP_SHARE_L1,
+			       &err);
+	if (!tg)
+		return err;
 
-	cpu_group_start = get_cpu_thread_group_start(cpu, &tg);
+	cpu_group_start = get_cpu_thread_group_start(cpu, tg);
 
 	if (unlikely(cpu_group_start == -1)) {
 		WARN_ON_ONCE(1);
-		err = -ENODATA;
-		goto out;
+		return -ENODATA;
 	}
 
 	zalloc_cpumask_var_node(&per_cpu(cpu_l1_cache_map, cpu),
 				GFP_KERNEL, cpu_to_node(cpu));
 
 	for (i = first_thread; i < first_thread + threads_per_core; i++) {
-		int i_group_start = get_cpu_thread_group_start(i, &tg);
+		int i_group_start = get_cpu_thread_group_start(i, tg);
 
 		if (unlikely(i_group_start == -1)) {
 			WARN_ON_ONCE(1);
-			err = -ENODATA;
-			goto out;
+			return -ENODATA;
 		}
 
 		if (i_group_start == cpu_group_start)
 			cpumask_set_cpu(i, per_cpu(cpu_l1_cache_map, cpu));
 	}
 
-out:
-	of_node_put(dn);
-	return err;
+	return 0;
 }
 
 static bool shared_caches;
-- 
1.9.4