sensors: dts: Assert special wakeup on idle cores while reading temperature

In P9, when a core enters a stop state, its clocks will be stopped
to save power and hence we will not be able to perform a scom
operation to read the DTS temperature sensor.  Hence, assert
a special wakeup on cores that have entered a stop state in order to
successfully complete the scom operation.

Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[rlippert@google.com: Clear special wakeup only when it succeeds]
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

1 files changed, 61 insertions, 13 deletions

diff --git a/hw/dts.c b/hw/dts.c
index a10df58..72a392b 100644
--- a/hw/dts.c
+++ b/hw/dts.c
@@ -20,6 +20,9 @@
 #include <dts.h>
 #include <skiboot.h>
 #include <opal-api.h>
+#include <opal-msg.h>
+#include <timer.h>
+#include <timebase.h>
 
 struct dts {
 	uint8_t		valid;
@@ -27,6 +30,14 @@ struct dts {
 	int16_t		temp;
 };
 
+/*
+ * Attributes for the core temperature sensor
+ */
+enum {
+	SENSOR_DTS_ATTR_TEMP_MAX,
+	SENSOR_DTS_ATTR_TEMP_TRIP
+};
+
 /* Different sensor locations */
 #define P7_CT_ZONE_LSU	0
 #define P7_CT_ZONE_ISU	1
@@ -225,8 +236,37 @@ static int dts_read_core_temp_p9(uint32_t pir, struct dts *dts)
 	return 0;
 }
 
-static int dts_read_core_temp(uint32_t pir, struct dts *dts)
+static void dts_async_read_temp(struct timer *t __unused, void *data,
+				u64 now __unused)
+{
+	struct dts dts;
+	int rc, swkup_rc;
+	struct cpu_thread *cpu = data;
+
+	swkup_rc = dctl_set_special_wakeup(cpu);
+
+	rc = dts_read_core_temp_p9(cpu->pir, &dts);
+	if (!rc) {
+		if (cpu->sensor_attr == SENSOR_DTS_ATTR_TEMP_MAX)
+			*(u32 *)cpu->sensor_data = dts.temp;
+		else if (cpu->sensor_attr == SENSOR_DTS_ATTR_TEMP_TRIP)
+			*(u32 *)cpu->sensor_data = dts.trip;
+	}
+
+	if (!swkup_rc)
+		dctl_clear_special_wakeup(cpu);
+
+	rc = opal_queue_msg(OPAL_MSG_ASYNC_COMP, NULL, NULL, cpu->token, rc);
+	if (rc)
+		prerror("Failed to queue async message\n");
+
+	cpu->dts_read_in_progress = false;
+}
+
+static int dts_read_core_temp(u32 pir, struct dts *dts, u8 attr,
+			      int token, u32 *sensor_data)
 {
+	struct cpu_thread *cpu;
 	int rc;
 
 	switch (proc_gen) {
@@ -236,8 +276,22 @@ static int dts_read_core_temp(uint32_t pir, struct dts *dts)
 	case proc_gen_p8:
 		rc = dts_read_core_temp_p8(pir, dts);
 		break;
-	case proc_gen_p9:
-		rc = dts_read_core_temp_p9(pir, dts);
+	case proc_gen_p9: /* Asynchronus read */
+		cpu = find_cpu_by_pir(pir);
+		if (!cpu)
+			return OPAL_PARAMETER;
+		lock(&cpu->dts_lock);
+		if (cpu->dts_read_in_progress) {
+			unlock(&cpu->dts_lock);
+			return OPAL_BUSY;
+		}
+		cpu->dts_read_in_progress = true;
+		cpu->sensor_attr = attr;
+		cpu->sensor_data = sensor_data;
+		cpu->token = token;
+		schedule_timer(&cpu->dts_timer, 0);
+		rc = OPAL_ASYNC_COMPLETION;
+		unlock(&cpu->dts_lock);
 		break;
 	default:
 		rc = OPAL_UNSUPPORTED;
@@ -303,20 +357,12 @@ enum sensor_dts_class {
 };
 
 /*
- * Attributes for the core temperature sensor
- */
-enum {
-	SENSOR_DTS_ATTR_TEMP_MAX,
-	SENSOR_DTS_ATTR_TEMP_TRIP
-};
-
-/*
  * Extract the centaur chip id which was truncated to fit in the
  * resource identifier field of the sensor handler
  */
 #define centaur_get_id(rid) (0x80000000 | ((rid) & 0x3ff))
 
-int64_t dts_sensor_read(uint32_t sensor_hndl, uint32_t *sensor_data)
+int64_t dts_sensor_read(u32 sensor_hndl, int token, u32 *sensor_data)
 {
 	uint8_t	attr = sensor_get_attr(sensor_hndl);
 	uint32_t rid = sensor_get_rid(sensor_hndl);
@@ -330,7 +376,7 @@ int64_t dts_sensor_read(uint32_t sensor_hndl, uint32_t *sensor_data)
 
 	switch (sensor_get_frc(sensor_hndl)) {
 	case SENSOR_DTS_CORE_TEMP:
-		rc = dts_read_core_temp(rid, &dts);
+		rc = dts_read_core_temp(rid, &dts, attr, token, sensor_data);
 		break;
 	case SENSOR_DTS_MEM_TEMP:
 		rc = dts_read_mem_temp(centaur_get_id(rid), &dts);
@@ -403,6 +449,8 @@ bool dts_sensor_create_nodes(struct dt_node *sensors)
 			dt_add_property_string(node, "sensor-type", "temp");
 			dt_add_property_cells(node, "ibm,pir", c->pir);
 			dt_add_property_string(node, "label", "Core");
+			init_timer(&c->dts_timer, dts_async_read_temp, c);
+			c->dts_read_in_progress = false;
 		}
 	}