firmware: arm_scmi: Ensure that the message-id supports fastchannel

Currently the perf and powercap protocol relies on the protocol domain
attributes, which just ensures that one fastchannel per domain, before
instantiating fastchannels for all possible message-ids. Fix this by
ensuring that each message-id supports fastchannel before initialization.

Logs:
  |  scmi: Failed to get FC for protocol 13 [MSG_ID:6 / RES_ID:0] - ret:-95. Using regular messaging
  |  scmi: Failed to get FC for protocol 13 [MSG_ID:6 / RES_ID:1] - ret:-95. Using regular messaging
  |  scmi: Failed to get FC for protocol 13 [MSG_ID:6 / RES_ID:2] - ret:-95. Using regular messaging

CC: stable@vger.kernel.org
Reported-by: Johan Hovold <johan+linaro@kernel.org>
Closes: https://lore.kernel.org/lkml/ZoQjAWse2YxwyRJv@hovoldconsulting.com/
Fixes: 6f9ea4dabd2d ("firmware: arm_scmi: Generalize the fast channel support")
Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
[Cristian: Modified the condition checked to establish support or not]
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Message-Id: <20250429141108.406045-2-cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

2 files changed, 45 insertions, 33 deletions

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 520aa5846916..cf2bc8b8d881 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -1730,6 +1730,39 @@ static int scmi_common_get_max_msg_size(const struct scmi_protocol_handle *ph)
 }
 
 /**
+ * scmi_protocol_msg_check  - Check protocol message attributes
+ *
+ * @ph: A reference to the protocol handle.
+ * @message_id: The ID of the message to check.
+ * @attributes: A parameter to optionally return the retrieved message
+ *		attributes, in case of Success.
+ *
+ * An helper to check protocol message attributes for a specific protocol
+ * and message pair.
+ *
+ * Return: 0 on SUCCESS
+ */
+static int scmi_protocol_msg_check(const struct scmi_protocol_handle *ph,
+				   u32 message_id, u32 *attributes)
+{
+	int ret;
+	struct scmi_xfer *t;
+
+	ret = xfer_get_init(ph, PROTOCOL_MESSAGE_ATTRIBUTES,
+			    sizeof(__le32), 0, &t);
+	if (ret)
+		return ret;
+
+	put_unaligned_le32(message_id, t->tx.buf);
+	ret = do_xfer(ph, t);
+	if (!ret && attributes)
+		*attributes = get_unaligned_le32(t->rx.buf);
+	xfer_put(ph, t);
+
+	return ret;
+}
+
+/**
  * struct scmi_iterator  - Iterator descriptor
  * @msg: A reference to the message TX buffer; filled by @prepare_message with
  *	 a proper custom command payload for each multi-part command request.
@@ -1870,6 +1903,7 @@ scmi_common_fastchannel_init(const struct scmi_protocol_handle *ph,
 	int ret;
 	u32 flags;
 	u64 phys_addr;
+	u32 attributes;
 	u8 size;
 	void __iomem *addr;
 	struct scmi_xfer *t;
@@ -1878,6 +1912,15 @@ scmi_common_fastchannel_init(const struct scmi_protocol_handle *ph,
 	struct scmi_msg_resp_desc_fc *resp;
 	const struct scmi_protocol_instance *pi = ph_to_pi(ph);
 
+	/* Check if the MSG_ID supports fastchannel */
+	ret = scmi_protocol_msg_check(ph, message_id, &attributes);
+	if (ret || !MSG_SUPPORTS_FASTCHANNEL(attributes)) {
+		dev_dbg(ph->dev,
+			"Skip FC init for 0x%02X/%d  domain:%d - ret:%d\n",
+			pi->proto->id, message_id, domain, ret);
+		return;
+	}
+
 	if (!p_addr) {
 		ret = -EINVAL;
 		goto err_out;
@@ -1995,39 +2038,6 @@ static void scmi_common_fastchannel_db_ring(struct scmi_fc_db_info *db)
 		SCMI_PROTO_FC_RING_DB(64);
 }
 
-/**
- * scmi_protocol_msg_check  - Check protocol message attributes
- *
- * @ph: A reference to the protocol handle.
- * @message_id: The ID of the message to check.
- * @attributes: A parameter to optionally return the retrieved message
- *		attributes, in case of Success.
- *
- * An helper to check protocol message attributes for a specific protocol
- * and message pair.
- *
- * Return: 0 on SUCCESS
- */
-static int scmi_protocol_msg_check(const struct scmi_protocol_handle *ph,
-				   u32 message_id, u32 *attributes)
-{
-	int ret;
-	struct scmi_xfer *t;
-
-	ret = xfer_get_init(ph, PROTOCOL_MESSAGE_ATTRIBUTES,
-			    sizeof(__le32), 0, &t);
-	if (ret)
-		return ret;
-
-	put_unaligned_le32(message_id, t->tx.buf);
-	ret = do_xfer(ph, t);
-	if (!ret && attributes)
-		*attributes = get_unaligned_le32(t->rx.buf);
-	xfer_put(ph, t);
-
-	return ret;
-}
-
 static const struct scmi_proto_helpers_ops helpers_ops = {
 	.extended_name_get = scmi_common_extended_name_get,
 	.get_max_msg_size = scmi_common_get_max_msg_size,
diff --git a/drivers/firmware/arm_scmi/protocols.h b/drivers/firmware/arm_scmi/protocols.h
index aaee57cdcd55..d62c4469d1fd 100644
--- a/drivers/firmware/arm_scmi/protocols.h
+++ b/drivers/firmware/arm_scmi/protocols.h
@@ -31,6 +31,8 @@
 
 #define SCMI_PROTOCOL_VENDOR_BASE	0x80
 
+#define MSG_SUPPORTS_FASTCHANNEL(x)	((x) & BIT(0))
+
 enum scmi_common_cmd {
 	PROTOCOL_VERSION = 0x0,
 	PROTOCOL_ATTRIBUTES = 0x1,