firmware: scpi: add device power domain support using genpd

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

Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Tested-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Tested-by: Jon Medhurst <tixy@linaro.org>
Reviewed-by: Jon Medhurst <tixy@linaro.org>
Reviewed-by: 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

@@ -27,6 +27,16 @@ config ARM_SCPI_PROTOCOL
 	  This protocol library provides interface for all the client drivers
 	  making use of the features offered by the SCP.
 
+config ARM_SCPI_POWER_DOMAIN
+	tristate "SCPI power domain driver"
+	depends on ARM_SCPI_PROTOCOL || COMPILE_TEST
+	default y
+	select PM_GENERIC_DOMAINS if PM
+	select PM_GENERIC_DOMAINS_OF if PM
+	help
+	  This enables support for the SCPI power domains which can be
+	  enabled or disabled via the SCP firmware
+
 config EDD
 	tristate "BIOS Enhanced Disk Drive calls determine boot disk"
 	depends on X86

drivers/firmware/Makefile

@@ -3,6 +3,7 @@
 #
 obj-$(CONFIG_ARM_PSCI_FW)	+= psci.o
 obj-$(CONFIG_ARM_SCPI_PROTOCOL)	+= arm_scpi.o
+obj-$(CONFIG_ARM_SCPI_POWER_DOMAIN) += scpi_pm_domain.o
 obj-$(CONFIG_DMI)		+= dmi_scan.o
 obj-$(CONFIG_DMI_SYSFS)		+= dmi-sysfs.o
 obj-$(CONFIG_EDD)		+= edd.o

drivers/firmware/scpi_pm_domain.c

@@ -0,0 +1,163 @@
+/*
+ * SCPI Generic power domain support.
+ *
+ * Copyright (C) 2016 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/pm_domain.h>
+#include <linux/scpi_protocol.h>
+
+struct scpi_pm_domain {
+	struct generic_pm_domain genpd;
+	struct scpi_ops *ops;
+	u32 domain;
+	char name[30];
+};
+
+/*
+ * These device power state values are not well-defined in the specification.
+ * In case, different implementations use different values, we can make these
+ * specific to compatibles rather than getting these values from device tree.
+ */
+enum scpi_power_domain_state {
+	SCPI_PD_STATE_ON = 0,
+	SCPI_PD_STATE_OFF = 3,
+};
+
+#define to_scpi_pd(gpd) container_of(gpd, struct scpi_pm_domain, genpd)
+
+static int scpi_pd_power(struct scpi_pm_domain *pd, bool power_on)
+{
+	int ret;
+	enum scpi_power_domain_state state;
+
+	if (power_on)
+		state = SCPI_PD_STATE_ON;
+	else
+		state = SCPI_PD_STATE_OFF;
+
+	ret = pd->ops->device_set_power_state(pd->domain, state);
+	if (ret)
+		return ret;
+
+	return !(state == pd->ops->device_get_power_state(pd->domain));
+}
+
+static int scpi_pd_power_on(struct generic_pm_domain *domain)
+{
+	struct scpi_pm_domain *pd = to_scpi_pd(domain);
+
+	return scpi_pd_power(pd, true);
+}
+
+static int scpi_pd_power_off(struct generic_pm_domain *domain)
+{
+	struct scpi_pm_domain *pd = to_scpi_pd(domain);
+
+	return scpi_pd_power(pd, false);
+}
+
+static int scpi_pm_domain_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct scpi_pm_domain *scpi_pd;
+	struct genpd_onecell_data *scpi_pd_data;
+	struct generic_pm_domain **domains;
+	struct scpi_ops *scpi_ops;
+	int ret, num_domains, i;
+
+	scpi_ops = get_scpi_ops();
+	if (!scpi_ops)
+		return -EPROBE_DEFER;
+
+	if (!np) {
+		dev_err(dev, "device tree node not found\n");
+		return -ENODEV;
+	}
+
+	if (!scpi_ops->device_set_power_state ||
+	    !scpi_ops->device_get_power_state) {
+		dev_err(dev, "power domains not supported in the firmware\n");
+		return -ENODEV;
+	}
+
+	ret = of_property_read_u32(np, "num-domains", &num_domains);
+	if (ret) {
+		dev_err(dev, "number of domains not found\n");
+		return -EINVAL;
+	}
+
+	scpi_pd = devm_kcalloc(dev, num_domains, sizeof(*scpi_pd), GFP_KERNEL);
+	if (!scpi_pd)
+		return -ENOMEM;
+
+	scpi_pd_data = devm_kzalloc(dev, sizeof(*scpi_pd_data), GFP_KERNEL);
+	if (!scpi_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++, scpi_pd++) {
+		domains[i] = &scpi_pd->genpd;
+
+		scpi_pd->domain = i;
+		scpi_pd->ops = scpi_ops;
+		sprintf(scpi_pd->name, "%s.%d", np->name, i);
+		scpi_pd->genpd.name = scpi_pd->name;
+		scpi_pd->genpd.power_off = scpi_pd_power_off;
+		scpi_pd->genpd.power_on = scpi_pd_power_on;
+
+		/*
+		 * Treat all power domains as off at boot.
+		 *
+		 * The SCP firmware itself may have switched on some domains,
+		 * but for reference counting purpose, keep it this way.
+		 */
+		pm_genpd_init(&scpi_pd->genpd, NULL, true);
+	}
+
+	scpi_pd_data->domains = domains;
+	scpi_pd_data->num_domains = num_domains;
+
+	of_genpd_add_provider_onecell(np, scpi_pd_data);
+
+	return 0;
+}
+
+static const struct of_device_id scpi_power_domain_ids[] = {
+	{ .compatible = "arm,scpi-power-domains", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, scpi_power_domain_ids);
+
+static struct platform_driver scpi_power_domain_driver = {
+	.driver	= {
+		.name = "scpi_power_domain",
+		.of_match_table = scpi_power_domain_ids,
+	},
+	.probe = scpi_pm_domain_probe,
+};
+module_platform_driver(scpi_power_domain_driver);
+
+MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
+MODULE_DESCRIPTION("ARM SCPI power domain driver");
+MODULE_LICENSE("GPL v2");