[RFC PATCH 2/3] powerpc/powernv: handle OPAL_SUCCESS return in opal_sensor_read

["Cédric Le Goater" <clg@fr.ibm.com>]

Currently, when a sensor value is read, the kernel calls OPAL, which in
turn builds a message for the FSP, and waits for a message back. However,
some sensors can be read synchronously (core temperatures for instance)
and don't need to wait for a response.

This patch modifies the opal call to accept an OPAL_SUCCESS return value
and not wait for a response if this is the case.

But, we still uselessly reserve a token (for the response) and take a
lock, which might raise the need of a new 'opal_sensor_read_sync' call.

Signed-off-by: Cédric Le Goater <clg@fr.ibm.com>
---
 arch/powerpc/platforms/powernv/opal-sensor.c |   29 +++++++++++++++++---------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal-sensor.c b/arch/powerpc/platforms/powernv/opal-sensor.c
index 544292f2020f..a4ed83a7dfb4 100644
--- a/arch/powerpc/platforms/powernv/opal-sensor.c
+++ b/arch/powerpc/platforms/powernv/opal-sensor.c
@@ -46,18 +46,27 @@ int opal_get_sensor_data(u32 sensor_hndl, u32 *sensor_data)
 
 	mutex_lock(&opal_sensor_mutex);
 	ret = opal_sensor_read(sensor_hndl, token, &data);
-	if (ret != OPAL_ASYNC_COMPLETION)
-		goto out_token;
+	switch (ret) {
+	case OPAL_ASYNC_COMPLETION:
+		ret = opal_async_wait_response(token, &msg);
+		if (ret) {
+			pr_err("%s: Failed to wait for the async response, %d\n",
+			       __func__, ret);
+			goto out_token;
+		}
 
-	ret = opal_async_wait_response(token, &msg);
-	if (ret) {
-		pr_err("%s: Failed to wait for the async response, %d\n",
-				__func__, ret);
-		goto out_token;
-	}
+		ret = be64_to_cpu(msg.params[1]);
+
+		*sensor_data = be32_to_cpu(data);
+		break;
 
-	*sensor_data = be32_to_cpu(data);
-	ret = be64_to_cpu(msg.params[1]);
+	case OPAL_SUCCESS:
+		*sensor_data = be32_to_cpu(data);
+		break;
+
+	default:
+		break;
+	}
 
 out_token:
 	mutex_unlock(&opal_sensor_mutex);
-- 
1.7.10.4