pmdomain: arm: Add the SCMI performance domain

To enable support for performance scaling (DVFS) for generic devices with
the SCMI performance protocol, let's add an SCMI performance domain. This
is being modelled as a genpd provider, with support for performance scaling
through genpd's ->set_performance_state() callback.

Note that, this adds the initial support that allows consumer drivers for
attached devices, to vote for a new performance state via calling the
dev_pm_genpd_set_performance_state(). However, this should be avoided as
it's in most cases preferred to use the OPP library to vote for a new OPP
instead. The support using the OPP library isn't part of this change, but
needs to be implemented from subsequent changes.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20230919121605.7304-1-ulf.hansson@linaro.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

MAINTAINERS

@@ -20902,6 +20902,7 @@ F:	drivers/clk/clk-sc[mp]i.c
 F:	drivers/cpufreq/sc[mp]i-cpufreq.c
 F:	drivers/firmware/arm_scmi/
 F:	drivers/firmware/arm_scpi.c
+F:	drivers/pmdomain/arm/
 F:	drivers/powercap/arm_scmi_powercap.c
 F:	drivers/regulator/scmi-regulator.c
 F:	drivers/reset/reset-scmi.c

drivers/firmware/arm_scmi/Kconfig

@@ -181,6 +181,18 @@ config ARM_SCMI_POWER_DOMAIN
 	  will be called scmi_pm_domain. Note this may needed early in boot
 	  before rootfs may be available.
 
+config ARM_SCMI_PERF_DOMAIN
+	tristate "SCMI performance 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 performance 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_perf_domain.
+
 config ARM_SCMI_POWER_CONTROL
 	tristate "SCMI system power control driver"
 	depends on ARM_SCMI_PROTOCOL || (COMPILE_TEST && OF)

drivers/pmdomain/Makefile

@@ -2,6 +2,7 @@
 obj-y					+= actions/
 obj-y					+= amlogic/
 obj-y					+= apple/
+obj-y					+= arm/
 obj-y					+= bcm/
 obj-y					+= imx/
 obj-y					+= mediatek/

drivers/pmdomain/arm/Makefile

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_ARM_SCMI_PERF_DOMAIN) += scmi_perf_domain.o

drivers/pmdomain/arm/scmi_perf_domain.c

@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SCMI performance domain support.
+ *
+ * Copyright (C) 2023 Linaro Ltd.
+ */
+
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/pm_domain.h>
+#include <linux/scmi_protocol.h>
+#include <linux/slab.h>
+
+struct scmi_perf_domain {
+	struct generic_pm_domain genpd;
+	const struct scmi_perf_proto_ops *perf_ops;
+	const struct scmi_protocol_handle *ph;
+	const struct scmi_perf_domain_info *info;
+	u32 domain_id;
+};
+
+#define to_scmi_pd(pd) container_of(pd, struct scmi_perf_domain, genpd)
+
+static int
+scmi_pd_set_perf_state(struct generic_pm_domain *genpd, unsigned int state)
+{
+	struct scmi_perf_domain *pd = to_scmi_pd(genpd);
+	int ret;
+
+	if (!pd->info->set_perf)
+		return 0;
+
+	if (!state)
+		return -EINVAL;
+
+	ret = pd->perf_ops->level_set(pd->ph, pd->domain_id, state, true);
+	if (ret)
+		dev_warn(&genpd->dev, "Failed with %d when trying to set %d perf level",
+			 ret, state);
+
+	return ret;
+}
+
+static int scmi_perf_domain_probe(struct scmi_device *sdev)
+{
+	struct device *dev = &sdev->dev;
+	const struct scmi_handle *handle = sdev->handle;
+	const struct scmi_perf_proto_ops *perf_ops;
+	struct scmi_protocol_handle *ph;
+	struct scmi_perf_domain *scmi_pd;
+	struct genpd_onecell_data *scmi_pd_data;
+	struct generic_pm_domain **domains;
+	int num_domains, i, ret = 0;
+
+	if (!handle)
+		return -ENODEV;
+
+	/* The OF node must specify us as a power-domain provider. */
+	if (!of_find_property(dev->of_node, "#power-domain-cells", NULL))
+		return 0;
+
+	perf_ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_PERF, &ph);
+	if (IS_ERR(perf_ops))
+		return PTR_ERR(perf_ops);
+
+	num_domains = perf_ops->num_domains_get(ph);
+	if (num_domains < 0) {
+		dev_warn(dev, "Failed with %d when getting num perf domains\n",
+			 num_domains);
+		return num_domains;
+	} else if (!num_domains) {
+		return 0;
+	}
+
+	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++) {
+		scmi_pd->info = perf_ops->info_get(ph, i);
+
+		scmi_pd->domain_id = i;
+		scmi_pd->perf_ops = perf_ops;
+		scmi_pd->ph = ph;
+		scmi_pd->genpd.name = scmi_pd->info->name;
+		scmi_pd->genpd.flags = GENPD_FLAG_ALWAYS_ON |
+				       GENPD_FLAG_OPP_TABLE_FW;
+		scmi_pd->genpd.set_performance_state = scmi_pd_set_perf_state;
+
+		ret = pm_genpd_init(&scmi_pd->genpd, NULL, false);
+		if (ret)
+			goto err;
+
+		domains[i] = &scmi_pd->genpd;
+	}
+
+	scmi_pd_data->domains = domains;
+	scmi_pd_data->num_domains = num_domains;
+
+	ret = of_genpd_add_provider_onecell(dev->of_node, scmi_pd_data);
+	if (ret)
+		goto err;
+
+	dev_set_drvdata(dev, scmi_pd_data);
+	dev_info(dev, "Initialized %d performance domains", num_domains);
+	return 0;
+err:
+	for (i--; i >= 0; i--)
+		pm_genpd_remove(domains[i]);
+	return ret;
+}
+
+static void scmi_perf_domain_remove(struct scmi_device *sdev)
+{
+	struct device *dev = &sdev->dev;
+	struct genpd_onecell_data *scmi_pd_data = dev_get_drvdata(dev);
+	int i;
+
+	of_genpd_del_provider(dev->of_node);
+
+	for (i = 0; i < scmi_pd_data->num_domains; i++)
+		pm_genpd_remove(scmi_pd_data->domains[i]);
+}
+
+static const struct scmi_device_id scmi_id_table[] = {
+	{ SCMI_PROTOCOL_PERF, "perf" },
+	{ },
+};
+MODULE_DEVICE_TABLE(scmi, scmi_id_table);
+
+static struct scmi_driver scmi_perf_domain_driver = {
+	.name		= "scmi-perf-domain",
+	.probe		= scmi_perf_domain_probe,
+	.remove		= scmi_perf_domain_remove,
+	.id_table	= scmi_id_table,
+};
+module_scmi_driver(scmi_perf_domain_driver);
+
+MODULE_AUTHOR("Ulf Hansson <ulf.hansson@linaro.org>");
+MODULE_DESCRIPTION("ARM SCMI perf domain driver");
+MODULE_LICENSE("GPL v2");