firmware: arm_scmi: Add SCMI v3.1 powercap protocol basic support

Add support for SCMI v3.1 powercap protocol, with the exception of powercap
fast channels, exposing all the new related powercap protocol operations as
usual in include/linux/scmi_protocol.h.

Link: https://lore.kernel.org/r/20220704102241.2988447-3-cristian.marussi@arm.com
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

5 files changed, 882 insertions, 1 deletions

diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
index faacd0ec7b81..9ea86f8cc8f7 100644
--- a/drivers/firmware/arm_scmi/Makefile
+++ b/drivers/firmware/arm_scmi/Makefile
@@ -7,7 +7,7 @@ scmi-transport-$(CONFIG_ARM_SCMI_TRANSPORT_SMC) += smc.o
 scmi-transport-$(CONFIG_ARM_SCMI_HAVE_MSG) += msg.o
 scmi-transport-$(CONFIG_ARM_SCMI_TRANSPORT_VIRTIO) += virtio.o
 scmi-transport-$(CONFIG_ARM_SCMI_TRANSPORT_OPTEE) += optee.o
-scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o voltage.o
+scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o voltage.o powercap.o
 scmi-module-objs := $(scmi-bus-y) $(scmi-driver-y) $(scmi-protocols-y) \
 		    $(scmi-transport-y)
 obj-$(CONFIG_ARM_SCMI_PROTOCOL) += scmi-module.o
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 1125a1f167a6..92a71e02b4cb 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -2485,6 +2485,7 @@ static int __init scmi_driver_init(void)
 	scmi_sensors_register();
 	scmi_voltage_register();
 	scmi_system_register();
+	scmi_powercap_register();
 
 	return platform_driver_register(&scmi_driver);
 }
@@ -2501,6 +2502,7 @@ static void __exit scmi_driver_exit(void)
 	scmi_sensors_unregister();
 	scmi_voltage_unregister();
 	scmi_system_unregister();
+	scmi_powercap_unregister();
 
 	scmi_bus_exit();
 
diff --git a/drivers/firmware/arm_scmi/powercap.c b/drivers/firmware/arm_scmi/powercap.c
new file mode 100644
index 000000000000..d71a1f6c2d8a
--- /dev/null
+++ b/drivers/firmware/arm_scmi/powercap.c
@@ -0,0 +1,753 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * System Control and Management Interface (SCMI) Powercap Protocol
+ *
+ * Copyright (C) 2022 ARM Ltd.
+ */
+
+#define pr_fmt(fmt) "SCMI Notifications POWERCAP - " fmt
+
+#include <linux/bitfield.h>
+#include <linux/module.h>
+#include <linux/scmi_protocol.h>
+
+#include "protocols.h"
+#include "notify.h"
+
+enum scmi_powercap_protocol_cmd {
+	POWERCAP_DOMAIN_ATTRIBUTES = 0x3,
+	POWERCAP_CAP_GET = 0x4,
+	POWERCAP_CAP_SET = 0x5,
+	POWERCAP_PAI_GET = 0x6,
+	POWERCAP_PAI_SET = 0x7,
+	POWERCAP_DOMAIN_NAME_GET = 0x8,
+	POWERCAP_MEASUREMENTS_GET = 0x9,
+	POWERCAP_CAP_NOTIFY = 0xa,
+	POWERCAP_MEASUREMENTS_NOTIFY = 0xb,
+	POWERCAP_DESCRIBE_FASTCHANNEL = 0xc,
+};
+
+struct scmi_msg_resp_powercap_domain_attributes {
+	__le32 attributes;
+#define SUPPORTS_POWERCAP_CAP_CHANGE_NOTIFY(x)		((x) & BIT(31))
+#define SUPPORTS_POWERCAP_MEASUREMENTS_CHANGE_NOTIFY(x)	((x) & BIT(30))
+#define SUPPORTS_ASYNC_POWERCAP_CAP_SET(x)		((x) & BIT(29))
+#define SUPPORTS_EXTENDED_NAMES(x)			((x) & BIT(28))
+#define SUPPORTS_POWERCAP_CAP_CONFIGURATION(x)		((x) & BIT(27))
+#define SUPPORTS_POWERCAP_MONITORING(x)			((x) & BIT(26))
+#define SUPPORTS_POWERCAP_PAI_CONFIGURATION(x)		((x) & BIT(25))
+#define POWERCAP_POWER_UNIT(x)				\
+		(FIELD_GET(GENMASK(24, 23), (x)))
+#define	SUPPORTS_POWER_UNITS_MW(x)			\
+		(POWERCAP_POWER_UNIT(x) == 0x2)
+#define	SUPPORTS_POWER_UNITS_UW(x)			\
+		(POWERCAP_POWER_UNIT(x) == 0x1)
+	u8 name[SCMI_SHORT_NAME_MAX_SIZE];
+	__le32 min_pai;
+	__le32 max_pai;
+	__le32 pai_step;
+	__le32 min_power_cap;
+	__le32 max_power_cap;
+	__le32 power_cap_step;
+	__le32 sustainable_power;
+	__le32 accuracy;
+	__le32 parent_id;
+};
+
+struct scmi_msg_powercap_set_cap_or_pai {
+	__le32 domain;
+	__le32 flags;
+#define CAP_SET_ASYNC		BIT(1)
+#define CAP_SET_IGNORE_DRESP	BIT(0)
+	__le32 value;
+};
+
+struct scmi_msg_resp_powercap_cap_set_complete {
+	__le32 domain;
+	__le32 power_cap;
+};
+
+struct scmi_msg_resp_powercap_meas_get {
+	__le32 power;
+	__le32 pai;
+};
+
+struct scmi_msg_powercap_notify_cap {
+	__le32 domain;
+	__le32 notify_enable;
+};
+
+struct scmi_msg_powercap_notify_thresh {
+	__le32 domain;
+	__le32 notify_enable;
+	__le32 power_thresh_low;
+	__le32 power_thresh_high;
+};
+
+struct scmi_powercap_cap_changed_notify_payld {
+	__le32 agent_id;
+	__le32 domain_id;
+	__le32 power_cap;
+	__le32 pai;
+};
+
+struct scmi_powercap_meas_changed_notify_payld {
+	__le32 agent_id;
+	__le32 domain_id;
+	__le32 power;
+};
+
+struct scmi_powercap_state {
+	bool meas_notif_enabled;
+	u64 thresholds;
+#define THRESH_LOW(p, id)				\
+	(lower_32_bits((p)->states[(id)].thresholds))
+#define THRESH_HIGH(p, id)				\
+	(upper_32_bits((p)->states[(id)].thresholds))
+};
+
+struct powercap_info {
+	u32 version;
+	int num_domains;
+	struct scmi_powercap_state *states;
+	struct scmi_powercap_info *powercaps;
+};
+
+static enum scmi_powercap_protocol_cmd evt_2_cmd[] = {
+	POWERCAP_CAP_NOTIFY,
+	POWERCAP_MEASUREMENTS_NOTIFY,
+};
+
+static int scmi_powercap_notify(const struct scmi_protocol_handle *ph,
+				u32 domain, int message_id, bool enable);
+
+static int
+scmi_powercap_attributes_get(const struct scmi_protocol_handle *ph,
+			     struct powercap_info *pi)
+{
+	int ret;
+	struct scmi_xfer *t;
+
+	ret = ph->xops->xfer_get_init(ph, PROTOCOL_ATTRIBUTES, 0,
+				      sizeof(u32), &t);
+	if (ret)
+		return ret;
+
+	ret = ph->xops->do_xfer(ph, t);
+	if (!ret) {
+		u32 attributes;
+
+		attributes = get_unaligned_le32(t->rx.buf);
+		pi->num_domains = FIELD_GET(GENMASK(15, 0), attributes);
+	}
+
+	ph->xops->xfer_put(ph, t);
+	return ret;
+}
+
+static inline int
+scmi_powercap_validate(unsigned int min_val, unsigned int max_val,
+		       unsigned int step_val, bool configurable)
+{
+	if (!min_val || !max_val)
+		return -EPROTO;
+
+	if ((configurable && min_val == max_val) ||
+	    (!configurable && min_val != max_val))
+		return -EPROTO;
+
+	if (min_val != max_val && !step_val)
+		return -EPROTO;
+
+	return 0;
+}
+
+static int
+scmi_powercap_domain_attributes_get(const struct scmi_protocol_handle *ph,
+				    struct powercap_info *pinfo, u32 domain)
+{
+	int ret;
+	u32 flags;
+	struct scmi_xfer *t;
+	struct scmi_powercap_info *dom_info = pinfo->powercaps + domain;
+	struct scmi_msg_resp_powercap_domain_attributes *resp;
+
+	ret = ph->xops->xfer_get_init(ph, POWERCAP_DOMAIN_ATTRIBUTES,
+				      sizeof(domain), sizeof(*resp), &t);
+	if (ret)
+		return ret;
+
+	put_unaligned_le32(domain, t->tx.buf);
+	resp = t->rx.buf;
+
+	ret = ph->xops->do_xfer(ph, t);
+	if (!ret) {
+		flags = le32_to_cpu(resp->attributes);
+
+		dom_info->id = domain;
+		dom_info->notify_powercap_cap_change =
+			SUPPORTS_POWERCAP_CAP_CHANGE_NOTIFY(flags);
+		dom_info->notify_powercap_measurement_change =
+			SUPPORTS_POWERCAP_MEASUREMENTS_CHANGE_NOTIFY(flags);
+		dom_info->async_powercap_cap_set =
+			SUPPORTS_ASYNC_POWERCAP_CAP_SET(flags);
+		dom_info->powercap_cap_config =
+			SUPPORTS_POWERCAP_CAP_CONFIGURATION(flags);
+		dom_info->powercap_monitoring =
+			SUPPORTS_POWERCAP_MONITORING(flags);
+		dom_info->powercap_pai_config =
+			SUPPORTS_POWERCAP_PAI_CONFIGURATION(flags);
+		dom_info->powercap_scale_mw =
+			SUPPORTS_POWER_UNITS_MW(flags);
+		dom_info->powercap_scale_uw =
+			SUPPORTS_POWER_UNITS_UW(flags);
+
+		strscpy(dom_info->name, resp->name, SCMI_SHORT_NAME_MAX_SIZE);
+
+		dom_info->min_pai = le32_to_cpu(resp->min_pai);
+		dom_info->max_pai = le32_to_cpu(resp->max_pai);
+		dom_info->pai_step = le32_to_cpu(resp->pai_step);
+		ret = scmi_powercap_validate(dom_info->min_pai,
+					     dom_info->max_pai,
+					     dom_info->pai_step,
+					     dom_info->powercap_pai_config);
+		if (ret) {
+			dev_err(ph->dev,
+				"Platform reported inconsistent PAI config for domain %d - %s\n",
+				dom_info->id, dom_info->name);
+			goto clean;
+		}
+
+		dom_info->min_power_cap = le32_to_cpu(resp->min_power_cap);
+		dom_info->max_power_cap = le32_to_cpu(resp->max_power_cap);
+		dom_info->power_cap_step = le32_to_cpu(resp->power_cap_step);
+		ret = scmi_powercap_validate(dom_info->min_power_cap,
+					     dom_info->max_power_cap,
+					     dom_info->power_cap_step,
+					     dom_info->powercap_cap_config);
+		if (ret) {
+			dev_err(ph->dev,
+				"Platform reported inconsistent CAP config for domain %d - %s\n",
+				dom_info->id, dom_info->name);
+			goto clean;
+		}
+
+		dom_info->sustainable_power =
+			le32_to_cpu(resp->sustainable_power);
+		dom_info->accuracy = le32_to_cpu(resp->accuracy);
+
+		dom_info->parent_id = le32_to_cpu(resp->parent_id);
+		if (dom_info->parent_id != SCMI_POWERCAP_ROOT_ZONE_ID &&
+		    (dom_info->parent_id >= pinfo->num_domains ||
+		     dom_info->parent_id == dom_info->id)) {
+			dev_err(ph->dev,
+				"Platform reported inconsistent parent ID for domain %d - %s\n",
+				dom_info->id, dom_info->name);
+			ret = -ENODEV;
+		}
+	}
+
+clean:
+	ph->xops->xfer_put(ph, t);
+
+	/*
+	 * If supported overwrite short name with the extended one;
+	 * on error just carry on and use already provided short name.
+	 */
+	if (!ret && SUPPORTS_EXTENDED_NAMES(flags))
+		ph->hops->extended_name_get(ph, POWERCAP_DOMAIN_NAME_GET,
+					    domain, dom_info->name,
+					    SCMI_MAX_STR_SIZE);
+
+	return ret;
+}
+
+static int scmi_powercap_num_domains_get(const struct scmi_protocol_handle *ph)
+{
+	struct powercap_info *pi = ph->get_priv(ph);
+
+	return pi->num_domains;
+}
+
+static const struct scmi_powercap_info *
+scmi_powercap_dom_info_get(const struct scmi_protocol_handle *ph, u32 domain_id)
+{
+	struct powercap_info *pi = ph->get_priv(ph);
+
+	if (domain_id >= pi->num_domains)
+		return NULL;
+
+	return pi->powercaps + domain_id;
+}
+
+static int scmi_powercap_cap_get(const struct scmi_protocol_handle *ph,
+				 u32 domain_id, u32 *power_cap)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct powercap_info *pi = ph->get_priv(ph);
+
+	if (!power_cap || domain_id >= pi->num_domains)
+		return -EINVAL;
+
+	ret = ph->xops->xfer_get_init(ph, POWERCAP_CAP_GET, sizeof(u32),
+				      sizeof(u32), &t);
+	if (ret)
+		return ret;
+
+	put_unaligned_le32(domain_id, t->tx.buf);
+	ret = ph->xops->do_xfer(ph, t);
+	if (!ret)
+		*power_cap = get_unaligned_le32(t->rx.buf);
+
+	ph->xops->xfer_put(ph, t);
+
+	return ret;
+}
+
+static int scmi_powercap_cap_set(const struct scmi_protocol_handle *ph,
+				 u32 domain_id, u32 power_cap,
+				 bool ignore_dresp)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct scmi_msg_powercap_set_cap_or_pai *msg;
+	const struct scmi_powercap_info *pc;
+
+	pc = scmi_powercap_dom_info_get(ph, domain_id);
+	if (!pc || !pc->powercap_cap_config || !power_cap ||
+	    power_cap < pc->min_power_cap ||
+	    power_cap > pc->max_power_cap)
+		return -EINVAL;
+
+	ret = ph->xops->xfer_get_init(ph, POWERCAP_CAP_SET,
+				      sizeof(*msg), 0, &t);
+	if (ret)
+		return ret;
+
+	msg = t->tx.buf;
+	msg->domain = cpu_to_le32(domain_id);
+	msg->flags =
+		cpu_to_le32(FIELD_PREP(CAP_SET_ASYNC, !!pc->async_powercap_cap_set) |
+			    FIELD_PREP(CAP_SET_IGNORE_DRESP, !!ignore_dresp));
+	msg->value = cpu_to_le32(power_cap);
+
+	if (!pc->async_powercap_cap_set || ignore_dresp) {
+		ret = ph->xops->do_xfer(ph, t);
+	} else {
+		ret = ph->xops->do_xfer_with_response(ph, t);
+		if (!ret) {
+			struct scmi_msg_resp_powercap_cap_set_complete *resp;
+
+			resp = t->rx.buf;
+			if (le32_to_cpu(resp->domain) == domain_id)
+				dev_dbg(ph->dev,
+					"Powercap ID %d CAP set async to %u\n",
+					domain_id,
+					get_unaligned_le32(&resp->power_cap));
+			else
+				ret = -EPROTO;
+		}
+	}
+
+	ph->xops->xfer_put(ph, t);
+	return ret;
+}
+
+static int scmi_powercap_pai_get(const struct scmi_protocol_handle *ph,
+				 u32 domain_id, u32 *pai)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct powercap_info *pi = ph->get_priv(ph);
+
+	if (!pai || domain_id >= pi->num_domains)
+		return -EINVAL;
+
+	ret = ph->xops->xfer_get_init(ph, POWERCAP_PAI_GET, sizeof(u32),
+				      sizeof(u32), &t);
+	if (ret)
+		return ret;
+
+	put_unaligned_le32(domain_id, t->tx.buf);
+	ret = ph->xops->do_xfer(ph, t);
+	if (!ret)
+		*pai = get_unaligned_le32(t->rx.buf);
+
+	ph->xops->xfer_put(ph, t);
+
+	return ret;
+}
+
+static int scmi_powercap_pai_set(const struct scmi_protocol_handle *ph,
+				 u32 domain_id, u32 pai)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct scmi_msg_powercap_set_cap_or_pai *msg;
+	const struct scmi_powercap_info *pc;
+
+	pc = scmi_powercap_dom_info_get(ph, domain_id);
+	if (!pc || !pc->powercap_pai_config || !pai ||
+	    pai < pc->min_pai || pai > pc->max_pai)
+		return -EINVAL;
+
+	ret = ph->xops->xfer_get_init(ph, POWERCAP_PAI_SET,
+				      sizeof(*msg), 0, &t);
+	if (ret)
+		return ret;
+
+	msg = t->tx.buf;
+	msg->domain = cpu_to_le32(domain_id);
+	msg->flags = cpu_to_le32(0);
+	msg->value = cpu_to_le32(pai);
+
+	ret = ph->xops->do_xfer(ph, t);
+
+	ph->xops->xfer_put(ph, t);
+	return ret;
+}
+
+static int scmi_powercap_measurements_get(const struct scmi_protocol_handle *ph,
+					  u32 domain_id, u32 *average_power,
+					  u32 *pai)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct scmi_msg_resp_powercap_meas_get *resp;
+	const struct scmi_powercap_info *pc;
+
+	pc = scmi_powercap_dom_info_get(ph, domain_id);
+	if (!pc || !pc->powercap_monitoring || !pai || !average_power)
+		return -EINVAL;
+
+	ret = ph->xops->xfer_get_init(ph, POWERCAP_MEASUREMENTS_GET,
+				      sizeof(u32), sizeof(*resp), &t);
+	if (ret)
+		return ret;
+
+	resp = t->rx.buf;
+	put_unaligned_le32(domain_id, t->tx.buf);
+	ret = ph->xops->do_xfer(ph, t);
+	if (!ret) {
+		*average_power = le32_to_cpu(resp->power);
+		*pai = le32_to_cpu(resp->pai);
+	}
+
+	ph->xops->xfer_put(ph, t);
+	return ret;
+}
+
+static int
+scmi_powercap_measurements_threshold_get(const struct scmi_protocol_handle *ph,
+					 u32 domain_id, u32 *power_thresh_low,
+					 u32 *power_thresh_high)
+{
+	struct powercap_info *pi = ph->get_priv(ph);
+
+	if (!power_thresh_low || !power_thresh_high ||
+	    domain_id >= pi->num_domains)
+		return -EINVAL;
+
+	*power_thresh_low =  THRESH_LOW(pi, domain_id);
+	*power_thresh_high = THRESH_HIGH(pi, domain_id);
+
+	return 0;
+}
+
+static int
+scmi_powercap_measurements_threshold_set(const struct scmi_protocol_handle *ph,
+					 u32 domain_id, u32 power_thresh_low,
+					 u32 power_thresh_high)
+{
+	int ret = 0;
+	struct powercap_info *pi = ph->get_priv(ph);
+
+	if (domain_id >= pi->num_domains ||
+	    power_thresh_low > power_thresh_high)
+		return -EINVAL;
+
+	/* Anything to do ? */
+	if (THRESH_LOW(pi, domain_id) == power_thresh_low &&
+	    THRESH_HIGH(pi, domain_id) == power_thresh_high)
+		return ret;
+
+	pi->states[domain_id].thresholds =
+		(FIELD_PREP(GENMASK_ULL(31, 0), power_thresh_low) |
+		 FIELD_PREP(GENMASK_ULL(63, 32), power_thresh_high));
+
+	/* Update thresholds if notification already enabled */
+	if (pi->states[domain_id].meas_notif_enabled)
+		ret = scmi_powercap_notify(ph, domain_id,
+					   POWERCAP_MEASUREMENTS_NOTIFY,
+					   true);
+
+	return ret;
+}
+
+static const struct scmi_powercap_proto_ops powercap_proto_ops = {
+	.num_domains_get = scmi_powercap_num_domains_get,
+	.info_get = scmi_powercap_dom_info_get,
+	.cap_get = scmi_powercap_cap_get,
+	.cap_set = scmi_powercap_cap_set,
+	.pai_get = scmi_powercap_pai_get,
+	.pai_set = scmi_powercap_pai_set,
+	.measurements_get = scmi_powercap_measurements_get,
+	.measurements_threshold_set = scmi_powercap_measurements_threshold_set,
+	.measurements_threshold_get = scmi_powercap_measurements_threshold_get,
+};
+
+static int scmi_powercap_notify(const struct scmi_protocol_handle *ph,
+				u32 domain, int message_id, bool enable)
+{
+	int ret;
+	struct scmi_xfer *t;
+
+	switch (message_id) {
+	case POWERCAP_CAP_NOTIFY:
+	{
+		struct scmi_msg_powercap_notify_cap *notify;
+
+		ret = ph->xops->xfer_get_init(ph, message_id,
+					      sizeof(*notify), 0, &t);
+		if (ret)
+			return ret;
+
+		notify = t->tx.buf;
+		notify->domain = cpu_to_le32(domain);
+		notify->notify_enable = cpu_to_le32(enable ? BIT(0) : 0);
+		break;
+	}
+	case POWERCAP_MEASUREMENTS_NOTIFY:
+	{
+		u32 low, high;
+		struct scmi_msg_powercap_notify_thresh *notify;
+
+		/*
+		 * Note that we have to pick the most recently configured
+		 * thresholds to build a proper POWERCAP_MEASUREMENTS_NOTIFY
+		 * enable request and we fail, complaining, if no thresholds
+		 * were ever set, since this is an indication the API has been
+		 * used wrongly.
+		 */
+		ret = scmi_powercap_measurements_threshold_get(ph, domain,
+							       &low, &high);
+		if (ret)
+			return ret;
+
+		if (enable && !low && !high) {
+			dev_err(ph->dev,
+				"Invalid Measurements Notify thresholds: %u/%u\n",
+				low, high);
+			return -EINVAL;
+		}
+
+		ret = ph->xops->xfer_get_init(ph, message_id,
+					      sizeof(*notify), 0, &t);
+		if (ret)
+			return ret;
+
+		notify = t->tx.buf;
+		notify->domain = cpu_to_le32(domain);
+		notify->notify_enable = cpu_to_le32(enable ? BIT(0) : 0);
+		notify->power_thresh_low = cpu_to_le32(low);
+		notify->power_thresh_high = cpu_to_le32(high);
+		break;
+	}
+	default:
+		return -EINVAL;
+	}
+
+	ret = ph->xops->do_xfer(ph, t);
+
+	ph->xops->xfer_put(ph, t);
+	return ret;
+}
+
+static int
+scmi_powercap_set_notify_enabled(const struct scmi_protocol_handle *ph,
+				 u8 evt_id, u32 src_id, bool enable)
+{
+	int ret, cmd_id;
+	struct powercap_info *pi = ph->get_priv(ph);
+
+	if (evt_id >= ARRAY_SIZE(evt_2_cmd) || src_id >= pi->num_domains)
+		return -EINVAL;
+
+	cmd_id = evt_2_cmd[evt_id];
+	ret = scmi_powercap_notify(ph, src_id, cmd_id, enable);
+	if (ret)
+		pr_debug("FAIL_ENABLED - evt[%X] dom[%d] - ret:%d\n",
+			 evt_id, src_id, ret);
+	else if (cmd_id == POWERCAP_MEASUREMENTS_NOTIFY)
+		/*
+		 * On success save the current notification enabled state, so
+		 * as to be able to properly update the notification thresholds
+		 * when they are modified on a domain for which measurement
+		 * notifications were currently enabled.
+		 *
+		 * This is needed because the SCMI Notification core machinery
+		 * and API does not support passing per-notification custom
+		 * arguments at callback registration time.
+		 *
+		 * Note that this can be done here with a simple flag since the
+		 * SCMI core Notifications code takes care of keeping proper
+		 * per-domain enables refcounting, so that this helper function
+		 * will be called only once (for enables) when the first user
+		 * registers a callback on this domain and once more (disable)
+		 * when the last user de-registers its callback.
+		 */
+		pi->states[src_id].meas_notif_enabled = enable;
+
+	return ret;
+}
+
+static void *
+scmi_powercap_fill_custom_report(const struct scmi_protocol_handle *ph,
+				 u8 evt_id, ktime_t timestamp,
+				 const void *payld, size_t payld_sz,
+				 void *report, u32 *src_id)
+{
+	void *rep = NULL;
+
+	switch (evt_id) {
+	case SCMI_EVENT_POWERCAP_CAP_CHANGED:
+	{
+		const struct scmi_powercap_cap_changed_notify_payld *p = payld;
+		struct scmi_powercap_cap_changed_report *r = report;
+
+		if (sizeof(*p) != payld_sz)
+			break;
+
+		r->timestamp = timestamp;
+		r->agent_id = le32_to_cpu(p->agent_id);
+		r->domain_id = le32_to_cpu(p->domain_id);
+		r->power_cap = le32_to_cpu(p->power_cap);
+		r->pai = le32_to_cpu(p->pai);
+		*src_id = r->domain_id;
+		rep = r;
+		break;
+	}
+	case SCMI_EVENT_POWERCAP_MEASUREMENTS_CHANGED:
+	{
+		const struct scmi_powercap_meas_changed_notify_payld *p = payld;
+		struct scmi_powercap_meas_changed_report *r = report;
+
+		if (sizeof(*p) != payld_sz)
+			break;
+
+		r->timestamp = timestamp;
+		r->agent_id = le32_to_cpu(p->agent_id);
+		r->domain_id = le32_to_cpu(p->domain_id);
+		r->power = le32_to_cpu(p->power);
+		*src_id = r->domain_id;
+		rep = r;
+		break;
+	}
+	default:
+		break;
+	}
+
+	return rep;
+}
+
+static int
+scmi_powercap_get_num_sources(const struct scmi_protocol_handle *ph)
+{
+	struct powercap_info *pi = ph->get_priv(ph);
+
+	if (!pi)
+		return -EINVAL;
+
+	return pi->num_domains;
+}
+
+static const struct scmi_event powercap_events[] = {
+	{
+		.id = SCMI_EVENT_POWERCAP_CAP_CHANGED,
+		.max_payld_sz =
+			sizeof(struct scmi_powercap_cap_changed_notify_payld),
+		.max_report_sz =
+			sizeof(struct scmi_powercap_cap_changed_report),
+	},
+	{
+		.id = SCMI_EVENT_POWERCAP_MEASUREMENTS_CHANGED,
+		.max_payld_sz =
+			sizeof(struct scmi_powercap_meas_changed_notify_payld),
+		.max_report_sz =
+			sizeof(struct scmi_powercap_meas_changed_report),
+	},
+};
+
+static const struct scmi_event_ops powercap_event_ops = {
+	.get_num_sources = scmi_powercap_get_num_sources,
+	.set_notify_enabled = scmi_powercap_set_notify_enabled,
+	.fill_custom_report = scmi_powercap_fill_custom_report,
+};
+
+static const struct scmi_protocol_events powercap_protocol_events = {
+	.queue_sz = SCMI_PROTO_QUEUE_SZ,
+	.ops = &powercap_event_ops,
+	.evts = powercap_events,
+	.num_events = ARRAY_SIZE(powercap_events),
+};
+
+static int
+scmi_powercap_protocol_init(const struct scmi_protocol_handle *ph)
+{
+	int domain, ret;
+	u32 version;
+	struct powercap_info *pinfo;
+
+	ret = ph->xops->version_get(ph, &version);
+	if (ret)
+		return ret;
+
+	dev_dbg(ph->dev, "Powercap Version %d.%d\n",
+		PROTOCOL_REV_MAJOR(version), PROTOCOL_REV_MINOR(version));
+
+	pinfo = devm_kzalloc(ph->dev, sizeof(*pinfo), GFP_KERNEL);
+	if (!pinfo)
+		return -ENOMEM;
+
+	ret = scmi_powercap_attributes_get(ph, pinfo);
+	if (ret)
+		return ret;
+
+	pinfo->powercaps = devm_kcalloc(ph->dev, pinfo->num_domains,
+					sizeof(*pinfo->powercaps),
+					GFP_KERNEL);
+	if (!pinfo->powercaps)
+		return -ENOMEM;
+
+	/*
+	 * Note that any failure in retrieving any domain attribute leads to
+	 * the whole Powercap protocol initialization failure: this way the
+	 * reported Powercap domains are all assured, when accessed, to be well
+	 * formed and correlated by sane parent-child relationship (if any).
+	 */
+	for (domain = 0; domain < pinfo->num_domains; domain++) {
+		ret = scmi_powercap_domain_attributes_get(ph, pinfo, domain);
+		if (ret)
+			return ret;
+	}
+
+	pinfo->states = devm_kcalloc(ph->dev, pinfo->num_domains,
+				     sizeof(*pinfo->states), GFP_KERNEL);
+	if (!pinfo->states)
+		return -ENOMEM;
+
+	pinfo->version = version;
+
+	return ph->set_priv(ph, pinfo);
+}
+
+static const struct scmi_protocol scmi_powercap = {
+	.id = SCMI_PROTOCOL_POWERCAP,
+	.owner = THIS_MODULE,
+	.instance_init = &scmi_powercap_protocol_init,
+	.ops = &powercap_proto_ops,
+	.events = &powercap_protocol_events,
+};
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(powercap, scmi_powercap)
diff --git a/drivers/firmware/arm_scmi/protocols.h b/drivers/firmware/arm_scmi/protocols.h
index 51c31379f9b3..99d36d503d1e 100644
--- a/drivers/firmware/arm_scmi/protocols.h
+++ b/drivers/firmware/arm_scmi/protocols.h
@@ -315,5 +315,6 @@ DECLARE_SCMI_REGISTER_UNREGISTER(reset);
 DECLARE_SCMI_REGISTER_UNREGISTER(sensors);
 DECLARE_SCMI_REGISTER_UNREGISTER(voltage);
 DECLARE_SCMI_REGISTER_UNREGISTER(system);
+DECLARE_SCMI_REGISTER_UNREGISTER(powercap);
 
 #endif /* _SCMI_PROTOCOLS_H */
diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 898488c7f185..95023dc8b3a3 100644
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h
@@ -561,6 +561,114 @@ struct scmi_voltage_proto_ops {
 };
 
 /**
+ * struct scmi_powercap_info  - Describe one available Powercap domain
+ *
+ * @id: Domain ID as advertised by the platform.
+ * @notify_powercap_cap_change: CAP change notification support.
+ * @notify_powercap_measurement_change: MEASUREMENTS change notifications
+ *				       support.
+ * @async_powercap_cap_set: Asynchronous CAP set support.
+ * @powercap_cap_config: CAP configuration support.
+ * @powercap_monitoring: Monitoring (measurements) support.
+ * @powercap_pai_config: PAI configuration support.
+ * @powercap_scale_mw: Domain reports power data in milliwatt units.
+ * @powercap_scale_uw: Domain reports power data in microwatt units.
+ *		       Note that, when both @powercap_scale_mw and
+ *		       @powercap_scale_uw are set to false, the domain
+ *		       reports power data on an abstract linear scale.
+ * @name: name assigned to the Powercap Domain by platform.
+ * @min_pai: Minimum configurable PAI.
+ * @max_pai: Maximum configurable PAI.
+ * @pai_step: Step size between two consecutive PAI values.
+ * @min_power_cap: Minimum configurable CAP.
+ * @max_power_cap: Maximum configurable CAP.
+ * @power_cap_step: Step size between two consecutive CAP values.
+ * @sustainable_power: Maximum sustainable power consumption for this domain
+ *		       under normal conditions.
+ * @accuracy: The accuracy with which the power is measured and reported in
+ *	      integral multiples of 0.001 percent.
+ * @parent_id: Identifier of the containing parent power capping domain, or the
+ *	       value 0xFFFFFFFF if this powercap domain is a root domain not
+ *	       contained in any other domain.
+ */
+struct scmi_powercap_info {
+	unsigned int id;
+	bool notify_powercap_cap_change;
+	bool notify_powercap_measurement_change;
+	bool async_powercap_cap_set;
+	bool powercap_cap_config;
+	bool powercap_monitoring;
+	bool powercap_pai_config;
+	bool powercap_scale_mw;
+	bool powercap_scale_uw;
+	char name[SCMI_MAX_STR_SIZE];
+	unsigned int min_pai;
+	unsigned int max_pai;
+	unsigned int pai_step;
+	unsigned int min_power_cap;
+	unsigned int max_power_cap;
+	unsigned int power_cap_step;
+	unsigned int sustainable_power;
+	unsigned int accuracy;
+#define SCMI_POWERCAP_ROOT_ZONE_ID     0xFFFFFFFFUL
+	unsigned int parent_id;
+};
+
+/**
+ * struct scmi_powercap_proto_ops - represents the various operations provided
+ * by SCMI Powercap Protocol
+ *
+ * @num_domains_get: get the count of powercap domains provided by SCMI.
+ * @info_get: get the information for the specified domain.
+ * @cap_get: get the current CAP value for the specified domain.
+ * @cap_set: set the CAP value for the specified domain to the provided value;
+ *	     if the domain supports setting the CAP with an asynchronous command
+ *	     this request will finally trigger an asynchronous transfer, but, if
+ *	     @ignore_dresp here is set to true, this call will anyway return
+ *	     immediately without waiting for the related delayed response.
+ * @pai_get: get the current PAI value for the specified domain.
+ * @pai_set: set the PAI value for the specified domain to the provided value.
+ * @measurements_get: retrieve the current average power measurements for the
+ *		      specified domain and the related PAI upon which is
+ *		      calculated.
+ * @measurements_threshold_set: set the desired low and high power thresholds
+ *				to be used when registering for notification
+ *				of type POWERCAP_MEASUREMENTS_NOTIFY with this
+ *				powercap domain.
+ *				Note that this must be called at least once
+ *				before registering any callback with the usual
+ *				@scmi_notify_ops; moreover, in case this method
+ *				is called with measurement notifications already
+ *				enabled it will also trigger, transparently, a
+ *				proper update of the power thresholds configured
+ *				in the SCMI backend server.
+ * @measurements_threshold_get: get the currently configured low and high power
+ *				thresholds used when registering callbacks for
+ *				notification POWERCAP_MEASUREMENTS_NOTIFY.
+ */
+struct scmi_powercap_proto_ops {
+	int (*num_domains_get)(const struct scmi_protocol_handle *ph);
+	const struct scmi_powercap_info __must_check *(*info_get)
+		(const struct scmi_protocol_handle *ph, u32 domain_id);
+	int (*cap_get)(const struct scmi_protocol_handle *ph, u32 domain_id,
+		       u32 *power_cap);
+	int (*cap_set)(const struct scmi_protocol_handle *ph, u32 domain_id,
+		       u32 power_cap, bool ignore_dresp);
+	int (*pai_get)(const struct scmi_protocol_handle *ph, u32 domain_id,
+		       u32 *pai);
+	int (*pai_set)(const struct scmi_protocol_handle *ph, u32 domain_id,
+		       u32 pai);
+	int (*measurements_get)(const struct scmi_protocol_handle *ph,
+				u32 domain_id, u32 *average_power, u32 *pai);
+	int (*measurements_threshold_set)(const struct scmi_protocol_handle *ph,
+					  u32 domain_id, u32 power_thresh_low,
+					  u32 power_thresh_high);
+	int (*measurements_threshold_get)(const struct scmi_protocol_handle *ph,
+					  u32 domain_id, u32 *power_thresh_low,
+					  u32 *power_thresh_high);
+};
+
+/**
  * struct scmi_notify_ops  - represents notifications' operations provided by
  * SCMI core
  * @devm_event_notifier_register: Managed registration of a notifier_block for
@@ -666,6 +774,7 @@ enum scmi_std_protocol {
 	SCMI_PROTOCOL_SENSOR = 0x15,
 	SCMI_PROTOCOL_RESET = 0x16,
 	SCMI_PROTOCOL_VOLTAGE = 0x17,
+	SCMI_PROTOCOL_POWERCAP = 0x18,
 };
 
 enum scmi_system_events {
@@ -767,6 +876,8 @@ enum scmi_notification_events {
 	SCMI_EVENT_RESET_ISSUED = 0x0,
 	SCMI_EVENT_BASE_ERROR_EVENT = 0x0,
 	SCMI_EVENT_SYSTEM_POWER_STATE_NOTIFIER = 0x0,
+	SCMI_EVENT_POWERCAP_CAP_CHANGED = 0x0,
+	SCMI_EVENT_POWERCAP_MEASUREMENTS_CHANGED = 0x1,
 };
 
 struct scmi_power_state_changed_report {
@@ -837,4 +948,18 @@ struct scmi_base_error_report {
 	unsigned long long	reports[];
 };
 
+struct scmi_powercap_cap_changed_report {
+	ktime_t		timestamp;
+	unsigned int	agent_id;
+	unsigned int	domain_id;
+	unsigned int	power_cap;
+	unsigned int	pai;
+};
+
+struct scmi_powercap_meas_changed_report {
+	ktime_t		timestamp;
+	unsigned int	agent_id;
+	unsigned int	domain_id;
+	unsigned int	power;
+};
 #endif /* _LINUX_SCMI_PROTOCOL_H */