[PATCH v2 1/6] misc: mpfs_syscontroller: add mailbox RX helper for service responses

[Jamie Gibbons <jamie.gibbons@microchip.com>]

The MPFS system controller run_service() helper only submits the mailbox
request but does not read back the response data. However, the caller
must explicitly receive the response.

Add a public system controller helper to receive mailbox service
responses to populate the response buffer after issuing a system
controller request.

Without this, the drivers copy uninitialised stack data instead of
mailbox response data, resulting in deterministic output.

Signed-off-by: Jamie Gibbons <jamie.gibbons@microchip.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
---
 drivers/misc/mpfs_syscontroller.c | 30 ++++++++++++++++++++++++++----
 include/mpfs-mailbox.h            |  2 ++
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/mpfs_syscontroller.c b/drivers/misc/mpfs_syscontroller.c
index f608d5518b0..8803263ca4c 100644
--- a/drivers/misc/mpfs_syscontroller.c
+++ b/drivers/misc/mpfs_syscontroller.c
@@ -85,6 +85,30 @@ int mpfs_syscontroller_run_service(struct mpfs_syscontroller_priv *sys_controlle
 }
 EXPORT_SYMBOL_GPL(mpfs_syscontroller_run_service);
 
+/**
+ * mpfs_syscontroller_recv_response() - Receive the MPFS system service response
+ * @sys_controller:	MPFS system controller instance
+ * @msg:			System service message
+ * @timeout_ms:		Timeout in milliseconds
+ *
+ * Receive the mailbox response for a previously issued MPFS system
+ * controller service request and populate the response buffer.
+ *
+ * Return: 0 if all goes good, else appropriate error message.
+ */
+int mpfs_syscontroller_recv_response(struct mpfs_syscontroller_priv *sys_controller, struct
+	mpfs_mss_msg * msg, unsigned long timeout_ms)
+{
+	int ret;
+
+	ret = mbox_recv(&sys_controller->chan, msg, timeout_ms);
+	if (ret)
+		dev_err(sys_controller->chan.dev, "Service failed: %d, abort. Failure: %u\n", ret,
+			msg->response->resp_status);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(mpfs_syscontroller_recv_response);
+
 /**
  * mpfs_syscontroller_read_sernum() - Use system service to read the device serial number
  * @sys_serv_priv:	system service private data
@@ -116,11 +140,9 @@ int mpfs_syscontroller_read_sernum(struct mpfs_sys_serv *sys_serv_priv, u8 *devi
 	}
 
 	/* Receive the response */
-	ret = mbox_recv(&sys_serv_priv->sys_controller->chan, &msg, timeoutsecs);
-	if (ret) {
-		dev_err(sys_serv_priv->sys_controller->chan.dev, "Service failed: %d, abort. Failure: %u\n", ret, msg.response->resp_status);
+	ret = mpfs_syscontroller_recv_response(sys_serv_priv->sys_controller, &msg, timeoutsecs);
+	if (ret)
 		return ret;
-	}
 
 	debug("%s: Read successful %s\n",
 	      __func__, sys_serv_priv->sys_controller->chan.dev->name);
diff --git a/include/mpfs-mailbox.h b/include/mpfs-mailbox.h
index c0ff327a4ce..39c998e4c8d 100644
--- a/include/mpfs-mailbox.h
+++ b/include/mpfs-mailbox.h
@@ -58,6 +58,8 @@ struct mpfs_sys_serv {
 };
 
 int mpfs_syscontroller_run_service(struct mpfs_syscontroller_priv *sys_controller, struct mpfs_mss_msg *msg);
+int mpfs_syscontroller_recv_response(struct mpfs_syscontroller_priv
+	*sys_controller, struct mpfs_mss_msg *msg, unsigned long timeout_ms);
 int mpfs_syscontroller_read_sernum(struct mpfs_sys_serv *sys_serv_priv, u8 *device_serial_number);
 void mpfs_syscontroller_process_dtbo(struct mpfs_sys_serv *sys_serv_priv);
 struct mpfs_syscontroller_priv *mpfs_syscontroller_get(struct udevice *dev);
-- 
2.43.0