1 files changed, 184 insertions, 3 deletions

diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c
index 6513ef2af66a..ff6d99e923a4 100644
--- a/drivers/cpuidle/cpuidle-pseries.c
+++ b/drivers/cpuidle/cpuidle-pseries.c
@@ -21,8 +21,9 @@
 #include <asm/runlatch.h>
 #include <asm/idle.h>
 #include <asm/plpar_wrappers.h>
+#include <asm/rtas.h>
 
-struct cpuidle_driver pseries_idle_driver = {
+static struct cpuidle_driver pseries_idle_driver = {
 	.name             = "pseries_idle",
 	.owner            = THIS_MODULE,
 };
@@ -86,19 +87,150 @@ static void check_and_cede_processor(void)
 	}
 }
 
+/*
+ * XCEDE: Extended CEDE states discovered through the
+ *        "ibm,get-systems-parameter" RTAS call with the token
+ *        CEDE_LATENCY_TOKEN
+ */
+
+/*
+ * Section 7.3.16 System Parameters Option of PAPR version 2.8.1 has a
+ * table with all the parameters to ibm,get-system-parameters.
+ * CEDE_LATENCY_TOKEN corresponds to the token value for Cede Latency
+ * Settings Information.
+ */
+#define CEDE_LATENCY_TOKEN	45
+
+/*
+ * If the platform supports the cede latency settings information system
+ * parameter it must provide the following information in the NULL terminated
+ * parameter string:
+ *
+ * a. The first byte is the length “N” of each cede latency setting record minus
+ *    one (zero indicates a length of 1 byte).
+ *
+ * b. For each supported cede latency setting a cede latency setting record
+ *    consisting of the first “N” bytes as per the following table.
+ *
+ *    -----------------------------
+ *    | Field           | Field   |
+ *    | Name            | Length  |
+ *    -----------------------------
+ *    | Cede Latency    | 1 Byte  |
+ *    | Specifier Value |         |
+ *    -----------------------------
+ *    | Maximum wakeup  |         |
+ *    | latency in      | 8 Bytes |
+ *    | tb-ticks        |         |
+ *    -----------------------------
+ *    | Responsive to   |         |
+ *    | external        | 1 Byte  |
+ *    | interrupts      |         |
+ *    -----------------------------
+ *
+ * This version has cede latency record size = 10.
+ *
+ * The structure xcede_latency_payload represents a) and b) with
+ * xcede_latency_record representing the table in b).
+ *
+ * xcede_latency_parameter is what gets returned by
+ * ibm,get-systems-parameter RTAS call when made with
+ * CEDE_LATENCY_TOKEN.
+ *
+ * These structures are only used to represent the data obtained by the RTAS
+ * call. The data is in big-endian.
+ */
+struct xcede_latency_record {
+	u8	hint;
+	__be64	latency_ticks;
+	u8	wake_on_irqs;
+} __packed;
+
+// Make space for 16 records, which "should be enough".
+struct xcede_latency_payload {
+	u8     record_size;
+	struct xcede_latency_record records[16];
+} __packed;
+
+struct xcede_latency_parameter {
+	__be16  payload_size;
+	struct xcede_latency_payload payload;
+	u8 null_char;
+} __packed;
+
+static unsigned int nr_xcede_records;
+static struct xcede_latency_parameter xcede_latency_parameter __initdata;
+
+static int __init parse_cede_parameters(void)
+{
+	struct xcede_latency_payload *payload;
+	u32 total_xcede_records_size;
+	u8 xcede_record_size;
+	u16 payload_size;
+	int ret, i;
+
+	ret = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
+			NULL, CEDE_LATENCY_TOKEN, __pa(&xcede_latency_parameter),
+			sizeof(xcede_latency_parameter));
+	if (ret) {
+		pr_err("xcede: Error parsing CEDE_LATENCY_TOKEN\n");
+		return ret;
+	}
+
+	payload_size = be16_to_cpu(xcede_latency_parameter.payload_size);
+	payload = &xcede_latency_parameter.payload;
+
+	xcede_record_size = payload->record_size + 1;
+
+	if (xcede_record_size != sizeof(struct xcede_latency_record)) {
+		pr_err("xcede: Expected record-size %lu. Observed size %u.\n",
+		       sizeof(struct xcede_latency_record), xcede_record_size);
+		return -EINVAL;
+	}
+
+	pr_info("xcede: xcede_record_size = %d\n", xcede_record_size);
+
+	/*
+	 * Since the payload_size includes the last NULL byte and the
+	 * xcede_record_size, the remaining bytes correspond to array of all
+	 * cede_latency settings.
+	 */
+	total_xcede_records_size = payload_size - 2;
+	nr_xcede_records = total_xcede_records_size / xcede_record_size;
+
+	for (i = 0; i < nr_xcede_records; i++) {
+		struct xcede_latency_record *record = &payload->records[i];
+		u64 latency_ticks = be64_to_cpu(record->latency_ticks);
+		u8 wake_on_irqs = record->wake_on_irqs;
+		u8 hint = record->hint;
+
+		pr_info("xcede: Record %d : hint = %u, latency = 0x%llx tb ticks, Wake-on-irq = %u\n",
+			i, hint, latency_ticks, wake_on_irqs);
+	}
+
+	return 0;
+}
+
+#define NR_DEDICATED_STATES	2 /* snooze, CEDE */
+static u8 cede_latency_hint[NR_DEDICATED_STATES];
+
 static int dedicated_cede_loop(struct cpuidle_device *dev,
 				struct cpuidle_driver *drv,
 				int index)
 {
+	u8 old_latency_hint;
 
 	pseries_idle_prolog();
 	get_lppaca()->donate_dedicated_cpu = 1;
+	old_latency_hint = get_lppaca()->cede_latency_hint;
+	get_lppaca()->cede_latency_hint = cede_latency_hint[index];
 
 	HMT_medium();
 	check_and_cede_processor();
 
 	local_irq_disable();
 	get_lppaca()->donate_dedicated_cpu = 0;
+	get_lppaca()->cede_latency_hint = old_latency_hint;
 
 	pseries_idle_epilog();
 
@@ -130,7 +262,7 @@ static int shared_cede_loop(struct cpuidle_device *dev,
 /*
  * States for dedicated partition case.
  */
-static struct cpuidle_state dedicated_states[] = {
+static struct cpuidle_state dedicated_states[NR_DEDICATED_STATES] = {
 	{ /* Snooze */
 		.name = "snooze",
 		.desc = "snooze",
@@ -211,6 +343,54 @@ static int pseries_cpuidle_driver_init(void)
 	return 0;
 }
 
+static void __init fixup_cede0_latency(void)
+{
+	struct xcede_latency_payload *payload;
+	u64 min_latency_us;
+	int i;
+
+	min_latency_us = dedicated_states[1].exit_latency; // CEDE latency
+
+	if (parse_cede_parameters())
+		return;
+
+	pr_info("cpuidle: Skipping the %d Extended CEDE idle states\n",
+		nr_xcede_records);
+
+	payload = &xcede_latency_parameter.payload;
+	for (i = 0; i < nr_xcede_records; i++) {
+		struct xcede_latency_record *record = &payload->records[i];
+		u64 latency_tb = be64_to_cpu(record->latency_ticks);
+		u64 latency_us = tb_to_ns(latency_tb) / NSEC_PER_USEC;
+
+		if (latency_us < min_latency_us)
+			min_latency_us = latency_us;
+	}
+
+	/*
+	 * By default, we assume that CEDE(0) has exit latency 10us,
+	 * since there is no way for us to query from the platform.
+	 *
+	 * However, if the wakeup latency of an Extended CEDE state is
+	 * smaller than 10us, then we can be sure that CEDE(0)
+	 * requires no more than that.
+	 *
+	 * Perform the fix-up.
+	 */
+	if (min_latency_us < dedicated_states[1].exit_latency) {
+		u64 cede0_latency = min_latency_us - 1;
+
+		if (cede0_latency <= 0)
+			cede0_latency = min_latency_us;
+
+		dedicated_states[1].exit_latency = cede0_latency;
+		dedicated_states[1].target_residency = 10 * (cede0_latency);
+		pr_info("cpuidle: Fixed up CEDE exit latency to %llu us\n",
+			cede0_latency);
+	}
+
+}
+
 /*
  * pseries_idle_probe()
  * Choose state table for shared versus dedicated partition
@@ -232,8 +412,9 @@ static int pseries_idle_probe(void)
 			cpuidle_state_table = shared_states;
 			max_idle_state = ARRAY_SIZE(shared_states);
 		} else {
+			fixup_cede0_latency();
 			cpuidle_state_table = dedicated_states;
-			max_idle_state = ARRAY_SIZE(dedicated_states);
+			max_idle_state = NR_DEDICATED_STATES;
 		}
 	} else
 		return -ENODEV;