@@ -86,6 +86,12 @@ struct scmi_xfers_info {
* @users: A refcount to track effective users of this protocol.
* @priv: Reference for optional protocol private data.
* @version: Protocol version supported by the platform as detected at runtime.
+ * @negotiated_version: When the platform supports a newer protocol version,
+ * the agent will try to negotiate with the platform the
+ * usage of the newest version known to it, since
+ * backward compatibility is NOT automatically assured.
+ * This field is NON-zero when a successful negotiation
+ * has completed.
* @ph: An embedded protocol handle that will be passed down to protocol
* initialization code to identify this instance.
*
@@ -99,6 +105,7 @@ struct scmi_protocol_instance {
refcount_t users;
void *priv;
unsigned int version;
+ unsigned int negotiated_version;
struct scmi_protocol_handle ph;
};
@@ -1815,6 +1822,44 @@ scmi_revision_area_get(const struct scmi_protocol_handle *ph)
return pi->handle->version;
}
+/**
+ * scmi_protocol_version_negotiate - Negotiate protocol version
+ *
+ * @ph: A reference to the protocol handle.
+ *
+ * An helper to negotiate a protocol version different from the latest
+ * advertised as supported from the platform: on Success backward
+ * compatibility is assured by the platform.
+ *
+ * Return: 0 on Success
+ */
+static int scmi_protocol_version_negotiate(struct scmi_protocol_handle *ph)
+{
+ int ret;
+ struct scmi_xfer *t;
+ struct scmi_protocol_instance *pi = ph_to_pi(ph);
+
+ /* At first check if NEGOTIATE_PROTOCOL_VERSION is supported ... */
+ ret = scmi_protocol_msg_check(ph, NEGOTIATE_PROTOCOL_VERSION, NULL);
+ if (ret)
+ return ret;
+
+ /* ... then attempt protocol version negotiation */
+ ret = xfer_get_init(ph, NEGOTIATE_PROTOCOL_VERSION,
+ sizeof(__le32), 0, &t);
+ if (ret)
+ return ret;
+
+ put_unaligned_le32(pi->proto->supported_version, t->tx.buf);
+ ret = do_xfer(ph, t);
+ if (!ret)
+ pi->negotiated_version = pi->proto->supported_version;
+
+ xfer_put(ph, t);
+
+ return ret;
+}
+
/**
* scmi_alloc_init_protocol_instance - Allocate and initialize a protocol
* instance descriptor.
@@ -1887,11 +1932,21 @@ scmi_alloc_init_protocol_instance(struct scmi_info *info,
devres_close_group(handle->dev, pi->gid);
dev_dbg(handle->dev, "Initialized protocol: 0x%X\n", pi->proto->id);
- if (pi->version > proto->supported_version)
- dev_warn(handle->dev,
- "Detected UNSUPPORTED higher version 0x%X for protocol 0x%X."
- "Backward compatibility is NOT assured.\n",
- pi->version, pi->proto->id);
+ if (pi->version > proto->supported_version) {
+ ret = scmi_protocol_version_negotiate(&pi->ph);
+ if (!ret) {
+ dev_info(handle->dev,
+ "Protocol 0x%X successfully negotiated version 0x%X\n",
+ proto->id, pi->negotiated_version);
+ } else {
+ dev_warn(handle->dev,
+ "Detected UNSUPPORTED higher version 0x%X for protocol 0x%X.\n",
+ pi->version, pi->proto->id);
+ dev_warn(handle->dev,
+ "Trying version 0x%X. Backward compatibility is NOT assured.\n",
+ pi->proto->supported_version);
+ }
+ }
return pi;
@@ -33,6 +33,7 @@ enum scmi_common_cmd {
PROTOCOL_VERSION = 0x0,
PROTOCOL_ATTRIBUTES = 0x1,
PROTOCOL_MESSAGE_ATTRIBUTES = 0x2,
+ NEGOTIATE_PROTOCOL_VERSION = 0x10,
};
/**
Freshly introduced NEGOTIATE_PROTOCOL_VERSION allows the agent to ascertain upfront if a specific, usually older, protocol version is supported by the platform. It is used by the agent in case the platform has advertised the support of a newer protocol version than the latest version supported by the agent, since backward compatibility cannot be automatically assumed. Emit a warning about possible incompatibility when negotiation was not possible or just print the successfully negotiated protocol. Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> --- drivers/firmware/arm_scmi/driver.c | 65 ++++++++++++++++++++++++--- drivers/firmware/arm_scmi/protocols.h | 1 + 2 files changed, 61 insertions(+), 5 deletions(-)