firmware: arm_scmi: Add protocol modularization support

Extend SCMI protocols accounting mechanism to address possible module
usage and add the support to possibly define new protocols as loadable
modules.

Keep the standard protocols built into the SCMI core.

Link: https://lore.kernel.org/r/20210316124903.35011-38-cristian.marussi@arm.com
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

1 files changed, 13 insertions, 4 deletions

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 563a64131035..c25c20c150dc 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -660,7 +660,8 @@ scmi_revision_area_get(const struct scmi_protocol_handle *ph)
  *
  * Context: Assumes to be called with @protocols_mtx already acquired.
  * Return: A reference to a freshly allocated and initialized protocol instance
- *	   or ERR_PTR on failure.
+ *	   or ERR_PTR on failure. On failure the @proto reference is at first
+ *	   put using @scmi_protocol_put() before releasing all the devres group.
  */
 static struct scmi_protocol_instance *
 scmi_alloc_init_protocol_instance(struct scmi_info *info,
@@ -673,8 +674,10 @@ scmi_alloc_init_protocol_instance(struct scmi_info *info,
 
 	/* Protocol specific devres group */
 	gid = devres_open_group(handle->dev, NULL, GFP_KERNEL);
-	if (!gid)
+	if (!gid) {
+		scmi_protocol_put(proto->id);
 		goto out;
+	}
 
 	pi = devm_kzalloc(handle->dev, sizeof(*pi), GFP_KERNEL);
 	if (!pi)
@@ -718,6 +721,8 @@ scmi_alloc_init_protocol_instance(struct scmi_info *info,
 	return pi;
 
 clean:
+	/* Take care to put the protocol module's owner before releasing all */
+	scmi_protocol_put(proto->id);
 	devres_release_group(handle->dev, gid);
 out:
 	return ERR_PTR(ret);
@@ -732,7 +737,9 @@ out:
  * instance, allocate and initialize all the needed structures while handling
  * resource allocation with a dedicated per-protocol devres subgroup.
  *
- * Return: A reference to an initialized protocol instance or error on failure.
+ * Return: A reference to an initialized protocol instance or error on failure:
+ *	   in particular returns -EPROBE_DEFER when the desired protocol could
+ *	   NOT be found.
  */
 static struct scmi_protocol_instance * __must_check
 scmi_get_protocol_instance(const struct scmi_handle *handle, u8 protocol_id)
@@ -753,7 +760,7 @@ scmi_get_protocol_instance(const struct scmi_handle *handle, u8 protocol_id)
 		if (proto)
 			pi = scmi_alloc_init_protocol_instance(info, proto);
 		else
-			pi = ERR_PTR(-ENODEV);
+			pi = ERR_PTR(-EPROBE_DEFER);
 	}
 	mutex_unlock(&info->protocols_mtx);
 
@@ -804,6 +811,8 @@ void scmi_protocol_release(const struct scmi_handle *handle, u8 protocol_id)
 
 		idr_remove(&info->protocols, protocol_id);
 
+		scmi_protocol_put(protocol_id);
+
 		devres_release_group(handle->dev, gid);
 		dev_dbg(handle->dev, "De-Initialized protocol: 0x%X\n",
 			protocol_id);