Quoting Lorenzo Pieralisi (2014-05-06 11:04:40)

...

+static int __init add_state_node(cpumask_t *cpumask,
+                                struct device_node *state_node)
+{
+       struct state_elem *el;
+       u32 tmp, val = 0;
+
+       pr_debug(" * %s...\n", state_node->full_name);
+
+       if (!state_cpus_valid(cpumask, state_node))
+               return -EINVAL;
+       /*
+        * Parse just the properties required to sort the states.
+        * Since we are missing a value defining the energy
+        * efficiency of a state, for now the sorting code uses
+        *
+        * min-residency-us+exit-latency-us
+        *
+        * as sorting rank.
+        */
+       if (of_property_read_u32(state_node, "min-residency-us",
+                                &tmp)) {
+               pr_debug(" * %s missing min-residency-us property\n",
+                        state_node->full_name);
+               return -EINVAL;
+       }
+
+       val += tmp;
+
+       if (of_property_read_u32(state_node, "exit-latency-us",
+                                &tmp)) {
+               pr_debug(" * %s missing exit-latency-us property\n",
+                            state_node->full_name);
+               return -EINVAL;
+       }
+
+       val += tmp;

Sorry if i'm rehashing old stuff, but I prefer not to use the
min-residency + exit-latency to sort.  I saw Rob's comment suggesting it
and your reply.  I'm not sure when it was decided.

Would it be possible to sort instead based on the order in the
cpus->cpu-idle-states?  If not, my preference would be to either use
index like you had before, or specify another sort order / rank value.

I think there's potential for us to create lower power states that
have lower min-residencies (reduced power consumption in the state,
allowing us to more quickly recover the higher entrance cost)
with higher exit latencies in such a way that the formula would not
sort as we expect.  Having a separate value would allow us to control
the sorting in those cases.

+
+/*

For kernel-doc, I think you need a /** here, and a () after the
of_init_idle_driver below.  Also maybe Return: instead of Returns:
and I think the return paragraph goes at the end, but am not positive.

kernel-doc-nano-HOWTO.txt

+ * of_init_idle_driver - Parse the DT idle states and initialize the
+ *                      idle driver states array
+ *
+ * @drv:         Pointer to CPU idle driver to be initialized
+ * @state_nodes:  Array of struct device_nodes to be initialized if
+ *               init_nodes == true. Must be sized CPUIDLE_STATE_MAX
+ * @start_idx:    First idle state index to be initialized
+ * @init_nodes:   Boolean to request device nodes initialization
+ *
+ * Returns:
+ *     0 on success
+ *     <0 on failure
+ *
+ *     On success the states array in the cpuidle driver contains
+ *     initialized entries in the states array, starting from index start_idx.
+ *     If init_nodes == true, on success the state_nodes array is initialized
+ *     with idle state DT node pointers, starting from index start_idx,
+ *     in a 1:1 relation with the idle driver states array.
+ */
+int __init of_init_idle_driver(struct cpuidle_driver *drv,
+                              struct device_node *state_nodes[],
+                              unsigned int start_idx, bool init_nodes)
+{

Thanks!

Sebastian