[PATCH v3 13/13] genpd: arm: Add the SCMI performance domain

[Ulf Hansson]

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@xxxxxxxxxx>
---

Changes in v3:
	- Move files to drivers/genpd/arm/ and update MAINTAINERS.
	- Updated the commit msg header.
	- Prevent setting performance level 0.
	- Initialize the genpd as always-on.
	- Note, the corresponding Kconfigs should be placed in the genpd dir
	too, but that's better suited on top or through a later-version.

---
 MAINTAINERS                          |   1 +
 drivers/firmware/arm_scmi/Kconfig    |  12 +++
 drivers/genpd/Makefile               |   1 +
 drivers/genpd/arm/Makefile           |   3 +
 drivers/genpd/arm/scmi_perf_domain.c | 150 +++++++++++++++++++++++++++
 5 files changed, 167 insertions(+)
 create mode 100644 drivers/genpd/arm/Makefile
 create mode 100644 drivers/genpd/arm/scmi_perf_domain.c

diff --git a/MAINTAINERS b/MAINTAINERS
index dff5d812f3ff..8995a160b240 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20705,6 +20705,7 @@ 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/genpd/arm/
 F:	drivers/powercap/arm_scmi_powercap.c
 F:	drivers/regulator/scmi-regulator.c
 F:	drivers/reset/reset-scmi.c
diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig
index ea0f5083ac47..706d1264d038 100644
--- a/drivers/firmware/arm_scmi/Kconfig
+++ b/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)
diff --git a/drivers/genpd/Makefile b/drivers/genpd/Makefile
index 666753676e5c..f0326b27b30b 100644
--- a/drivers/genpd/Makefile
+++ b/drivers/genpd/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/
diff --git a/drivers/genpd/arm/Makefile b/drivers/genpd/arm/Makefile
new file mode 100644
index 000000000000..7128db96deac
--- /dev/null
+++ b/drivers/genpd/arm/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_ARM_SCMI_PERF_DOMAIN) += scmi_perf_domain.o
diff --git a/drivers/genpd/arm/scmi_perf_domain.c b/drivers/genpd/arm/scmi_perf_domain.c
new file mode 100644
index 000000000000..aa100270500f
--- /dev/null
+++ b/drivers/genpd/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@xxxxxxxxxx>");
+MODULE_DESCRIPTION("ARM SCMI perf domain driver");
+MODULE_LICENSE("GPL v2");
-- 
2.34.1