firmware: arm_scmi: Populate fast channel rate_limit

Arm SCMI spec. v3.2, s4.5.3.12 PERFORMANCE_DESCRIBE_FASTCHANNEL
defines a per-domain rate_limit for performance requests:
"""
Rate Limit in microseconds, indicating the minimum time
required between successive requests. A value of 0
indicates that this field is not applicable or supported
on the platform.
""""
The field is first defined in SCMI v2.0.

Add support to fetch this value and advertise it through
a fast_switch_rate_limit() callback.
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/firmware/arm_scmi/driver.c

@@ -1617,7 +1617,7 @@ static void
 scmi_common_fastchannel_init(const struct scmi_protocol_handle *ph,
 			     u8 describe_id, u32 message_id, u32 valid_size,
 			     u32 domain, void __iomem **p_addr,
-			     struct scmi_fc_db_info **p_db)
+			     struct scmi_fc_db_info **p_db, u32 *rate_limit)
 {
 	int ret;
 	u32 flags;
@@ -1661,6 +1661,9 @@ scmi_common_fastchannel_init(const struct scmi_protocol_handle *ph,
 		goto err_xfer;
 	}
 
+	if (rate_limit)
+		*rate_limit = le32_to_cpu(resp->rate_limit) & GENMASK(19, 0);
+
 	phys_addr = le32_to_cpu(resp->chan_addr_low);
 	phys_addr |= (u64)le32_to_cpu(resp->chan_addr_high) << 32;
 	addr = devm_ioremap(ph->dev, phys_addr, size);

drivers/firmware/arm_scmi/perf.c

@@ -776,23 +776,27 @@ static void scmi_perf_domain_init_fc(const struct scmi_protocol_handle *ph,
 
 	ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
 				   PERF_LEVEL_GET, 4, dom->id,
-				   &fc[PERF_FC_LEVEL].get_addr, NULL);
+				   &fc[PERF_FC_LEVEL].get_addr, NULL,
+				   &fc[PERF_FC_LEVEL].rate_limit);
 
 	ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
 				   PERF_LIMITS_GET, 8, dom->id,
-				   &fc[PERF_FC_LIMIT].get_addr, NULL);
+				   &fc[PERF_FC_LIMIT].get_addr, NULL,
+				   &fc[PERF_FC_LIMIT].rate_limit);
 
 	if (dom->info.set_perf)
 		ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
 					   PERF_LEVEL_SET, 4, dom->id,
 					   &fc[PERF_FC_LEVEL].set_addr,
-					   &fc[PERF_FC_LEVEL].set_db);
+					   &fc[PERF_FC_LEVEL].set_db,
+					   &fc[PERF_FC_LEVEL].rate_limit);
 
 	if (dom->set_limits)
 		ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
 					   PERF_LIMITS_SET, 8, dom->id,
 					   &fc[PERF_FC_LIMIT].set_addr,
-					   &fc[PERF_FC_LIMIT].set_db);
+					   &fc[PERF_FC_LIMIT].set_db,
+					   &fc[PERF_FC_LIMIT].rate_limit);
 
 	dom->fc_info = fc;
 }
@@ -961,6 +965,25 @@ static bool scmi_fast_switch_possible(const struct scmi_protocol_handle *ph,
 	return dom->fc_info && dom->fc_info[PERF_FC_LEVEL].set_addr;
 }
 
+static int scmi_fast_switch_rate_limit(const struct scmi_protocol_handle *ph,
+				       u32 domain, u32 *rate_limit)
+{
+	struct perf_dom_info *dom;
+
+	if (!rate_limit)
+		return -EINVAL;
+
+	dom = scmi_perf_domain_lookup(ph, domain);
+	if (IS_ERR(dom))
+		return PTR_ERR(dom);
+
+	if (!dom->fc_info)
+		return -EINVAL;
+
+	*rate_limit = dom->fc_info[PERF_FC_LEVEL].rate_limit;
+	return 0;
+}
+
 static enum scmi_power_scale
 scmi_power_scale_get(const struct scmi_protocol_handle *ph)
 {
@@ -983,6 +1006,7 @@ static const struct scmi_perf_proto_ops perf_proto_ops = {
 	.freq_get = scmi_dvfs_freq_get,
 	.est_power_get = scmi_dvfs_est_power_get,
 	.fast_switch_possible = scmi_fast_switch_possible,
+	.fast_switch_rate_limit = scmi_fast_switch_rate_limit,
 	.power_scale_get = scmi_power_scale_get,
 };
 

drivers/firmware/arm_scmi/powercap.c

@@ -703,20 +703,24 @@ static void scmi_powercap_domain_init_fc(const struct scmi_protocol_handle *ph,
 	ph->hops->fastchannel_init(ph, POWERCAP_DESCRIBE_FASTCHANNEL,
 				   POWERCAP_CAP_SET, 4, domain,
 				   &fc[POWERCAP_FC_CAP].set_addr,
-				   &fc[POWERCAP_FC_CAP].set_db);
+				   &fc[POWERCAP_FC_CAP].set_db,
+				   &fc[POWERCAP_FC_CAP].rate_limit);
 
 	ph->hops->fastchannel_init(ph, POWERCAP_DESCRIBE_FASTCHANNEL,
 				   POWERCAP_CAP_GET, 4, domain,
-				   &fc[POWERCAP_FC_CAP].get_addr, NULL);
+				   &fc[POWERCAP_FC_CAP].get_addr, NULL,
+				   &fc[POWERCAP_FC_CAP].rate_limit);
 
 	ph->hops->fastchannel_init(ph, POWERCAP_DESCRIBE_FASTCHANNEL,
 				   POWERCAP_PAI_SET, 4, domain,
 				   &fc[POWERCAP_FC_PAI].set_addr,
-				   &fc[POWERCAP_FC_PAI].set_db);
+				   &fc[POWERCAP_FC_PAI].set_db,
+				   &fc[POWERCAP_FC_PAI].rate_limit);
 
 	ph->hops->fastchannel_init(ph, POWERCAP_DESCRIBE_FASTCHANNEL,
 				   POWERCAP_PAI_GET, 4, domain,
-				   &fc[POWERCAP_FC_PAI].get_addr, NULL);
+				   &fc[POWERCAP_FC_PAI].get_addr, NULL,
+				   &fc[POWERCAP_PAI_GET].rate_limit);
 
 	*p_fc = fc;
 }

drivers/firmware/arm_scmi/protocols.h

@@ -234,6 +234,7 @@ struct scmi_fc_info {
 	void __iomem *set_addr;
 	void __iomem *get_addr;
 	struct scmi_fc_db_info *set_db;
+	u32 rate_limit;
 };
 
 /**
@@ -268,7 +269,8 @@ struct scmi_proto_helpers_ops {
 				 u8 describe_id, u32 message_id,
 				 u32 valid_size, u32 domain,
 				 void __iomem **p_addr,
-				 struct scmi_fc_db_info **p_db);
+				 struct scmi_fc_db_info **p_db,
+				 u32 *rate_limit);
 	void (*fastchannel_db_ring)(struct scmi_fc_db_info *db);
 };
 

include/linux/scmi_protocol.h

@@ -139,6 +139,8 @@ struct scmi_perf_domain_info {
  *	at a given frequency
  * @fast_switch_possible: indicates if fast DVFS switching is possible or not
  *	for a given device
+ * @fast_switch_rate_limit: gets the minimum time (us) required between
+ *	successive fast_switching requests
  * @power_scale_mw_get: indicates if the power values provided are in milliWatts
  *	or in some other (abstract) scale
  */
@@ -168,6 +170,8 @@ struct scmi_perf_proto_ops {
 			     unsigned long *rate, unsigned long *power);
 	bool (*fast_switch_possible)(const struct scmi_protocol_handle *ph,
 				     u32 domain);
+	int (*fast_switch_rate_limit)(const struct scmi_protocol_handle *ph,
+				      u32 domain, u32 *rate_limit);
 	enum scmi_power_scale (*power_scale_get)(const struct scmi_protocol_handle *ph);
 };