firmware: arm_scmi: Populate fastchannel info only if set operations are allowed

Certain SCMI performance domains may have restrictions on the set level
and/or limits operation. If the SCMI domain supports fastchannel and the
set operations are not allowed, then any attempts to fetch the fastchannel
information for set level and/or limits operation will result in the
SCMI platform returning SCMI_ERR_SUPPORT. However, since this information
about the domain is already known to the agent(OSPM here) obtained via
PERF_DOMAIN_ATTRIBUTES, the agent(OSPM) can avoid calls to the firmware
trying to fetch the fastchannel information for the same.

Add those checks and skip querying the fastchannel information from the
firmware based on the information collected during the domain enumeration
stage.

Link: https://lore.kernel.org/r/20231113143252.37160-1-sudeep.holla@arm.comReviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/perf.c

@@ -762,29 +762,36 @@ static void scmi_perf_domain_init_fc(const struct scmi_protocol_handle *ph,
 				     u32 domain, struct scmi_fc_info **p_fc)
 {
 	struct scmi_fc_info *fc;
+	struct perf_dom_info *dom;
+
+	dom = scmi_perf_domain_lookup(ph, domain);
+	if (IS_ERR(dom))
+		return;
 
 	fc = devm_kcalloc(ph->dev, PERF_FC_MAX, sizeof(*fc), GFP_KERNEL);
 	if (!fc)
 		return;
 
-	ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
-				   PERF_LEVEL_SET, 4, domain,
-				   &fc[PERF_FC_LEVEL].set_addr,
-				   &fc[PERF_FC_LEVEL].set_db);
-
 	ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
 				   PERF_LEVEL_GET, 4, domain,
 				   &fc[PERF_FC_LEVEL].get_addr, NULL);
 
-	ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
-				   PERF_LIMITS_SET, 8, domain,
-				   &fc[PERF_FC_LIMIT].set_addr,
-				   &fc[PERF_FC_LIMIT].set_db);
-
 	ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
 				   PERF_LIMITS_GET, 8, domain,
 				   &fc[PERF_FC_LIMIT].get_addr, NULL);
 
+	if (dom->info.set_perf)
+		ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
+					   PERF_LEVEL_SET, 4, domain,
+					   &fc[PERF_FC_LEVEL].set_addr,
+					   &fc[PERF_FC_LEVEL].set_db);
+
+	if (dom->set_limits)
+		ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
+					   PERF_LIMITS_SET, 8, domain,
+					   &fc[PERF_FC_LIMIT].set_addr,
+					   &fc[PERF_FC_LIMIT].set_db);
+
 	*p_fc = fc;
 }