firmware: arm_scmi: add device power domain support using genpd

This patch hooks up the support for device power domain provided by
SCMI using the Linux generic power domain infrastructure.

Cc: Kevin Hilman <khilman@baylibre.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/Kconfig

@@ -40,6 +40,19 @@ config ARM_SCMI_PROTOCOL
 	  This protocol library provides interface for all the client drivers
 	  making use of the features offered by the SCMI.
 
+config ARM_SCMI_POWER_DOMAIN
+	tristate "SCMI power domain driver"
+	depends on ARM_SCMI_PROTOCOL || (COMPILE_TEST && OF)
+	default y
+	select PM_GENERIC_DOMAINS if PM
+	help
+	  This enables support for the SCMI power domains which can be
+	  enabled or disabled via the SCP firmware
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called scmi_pm_domain. Note this may needed early in boot
+	  before rootfs may be available.
+
 config ARM_SCPI_PROTOCOL
 	tristate "ARM System Control and Power Interface (SCPI) Message Protocol"
 	depends on ARM || ARM64 || COMPILE_TEST

drivers/firmware/arm_scmi/Makefile

@@ -2,3 +2,4 @@ obj-y	= scmi-bus.o scmi-driver.o scmi-protocols.o
 scmi-bus-y = bus.o
 scmi-driver-y = driver.o
 scmi-protocols-y = base.o clock.o perf.o power.o sensors.o
+obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o

drivers/firmware/arm_scmi/scmi_pm_domain.c

@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SCMI Generic power domain support.
+ *
+ * Copyright (C) 2018 ARM Ltd.
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/pm_domain.h>
+#include <linux/scmi_protocol.h>
+
+struct scmi_pm_domain {
+	struct generic_pm_domain genpd;
+	const struct scmi_handle *handle;
+	const char *name;
+	u32 domain;
+};
+
+#define to_scmi_pd(gpd) container_of(gpd, struct scmi_pm_domain, genpd)
+
+static int scmi_pd_power(struct generic_pm_domain *domain, bool power_on)
+{
+	int ret;
+	u32 state, ret_state;
+	struct scmi_pm_domain *pd = to_scmi_pd(domain);
+	const struct scmi_power_ops *ops = pd->handle->power_ops;
+
+	if (power_on)
+		state = SCMI_POWER_STATE_GENERIC_ON;
+	else
+		state = SCMI_POWER_STATE_GENERIC_OFF;
+
+	ret = ops->state_set(pd->handle, pd->domain, state);
+	if (!ret)
+		ret = ops->state_get(pd->handle, pd->domain, &ret_state);
+	if (!ret && state != ret_state)
+		return -EIO;
+
+	return ret;
+}
+
+static int scmi_pd_power_on(struct generic_pm_domain *domain)
+{
+	return scmi_pd_power(domain, true);
+}
+
+static int scmi_pd_power_off(struct generic_pm_domain *domain)
+{
+	return scmi_pd_power(domain, false);
+}
+
+static int scmi_pm_domain_probe(struct scmi_device *sdev)
+{
+	int num_domains, i;
+	struct device *dev = &sdev->dev;
+	struct device_node *np = dev->of_node;
+	struct scmi_pm_domain *scmi_pd;
+	struct genpd_onecell_data *scmi_pd_data;
+	struct generic_pm_domain **domains;
+	const struct scmi_handle *handle = sdev->handle;
+
+	if (!handle || !handle->power_ops)
+		return -ENODEV;
+
+	num_domains = handle->power_ops->num_domains_get(handle);
+	if (num_domains < 0) {
+		dev_err(dev, "number of domains not found\n");
+		return num_domains;
+	}
+
+	scmi_pd = devm_kcalloc(dev, num_domains, sizeof(*scmi_pd), GFP_KERNEL);
+	if (!scmi_pd)
+		return -ENOMEM;
+
+	scmi_pd_data = devm_kzalloc(dev, sizeof(*scmi_pd_data), GFP_KERNEL);
+	if (!scmi_pd_data)
+		return -ENOMEM;
+
+	domains = devm_kcalloc(dev, num_domains, sizeof(*domains), GFP_KERNEL);
+	if (!domains)
+		return -ENOMEM;
+
+	for (i = 0; i < num_domains; i++, scmi_pd++) {
+		u32 state;
+
+		domains[i] = &scmi_pd->genpd;
+
+		scmi_pd->domain = i;
+		scmi_pd->handle = handle;
+		scmi_pd->name = handle->power_ops->name_get(handle, i);
+		scmi_pd->genpd.name = scmi_pd->name;
+		scmi_pd->genpd.power_off = scmi_pd_power_off;
+		scmi_pd->genpd.power_on = scmi_pd_power_on;
+
+		if (handle->power_ops->state_get(handle, i, &state)) {
+			dev_warn(dev, "failed to get state for domain %d\n", i);
+			continue;
+		}
+
+		pm_genpd_init(&scmi_pd->genpd, NULL,
+			      state == SCMI_POWER_STATE_GENERIC_OFF);
+	}
+
+	scmi_pd_data->domains = domains;
+	scmi_pd_data->num_domains = num_domains;
+
+	of_genpd_add_provider_onecell(np, scmi_pd_data);
+
+	return 0;
+}
+
+static const struct scmi_device_id scmi_id_table[] = {
+	{ SCMI_PROTOCOL_POWER },
+	{ },
+};
+MODULE_DEVICE_TABLE(scmi, scmi_id_table);
+
+static struct scmi_driver scmi_power_domain_driver = {
+	.name = "scmi-power-domain",
+	.probe = scmi_pm_domain_probe,
+	.id_table = scmi_id_table,
+};
+module_scmi_driver(scmi_power_domain_driver);
+
+MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
+MODULE_DESCRIPTION("ARM SCMI power domain driver");
+MODULE_LICENSE("GPL v2");