[RFC PATCH v3 5/7] devfreq: exynos-bus: Add interconnect functionality to exynos-bus

["Artur Świgoń" <a.swigon@samsung.com>]

This patch adds interconnect functionality to the exynos-bus devfreq
driver.

The SoC topology is a graph (or, more specifically, a tree) and its
edges are specified using the 'exynos,interconnect-parent-node' in the
DT. Due to unspecified relative probing order, -EPROBE_DEFER may be
propagated to ensure that the parent is probed before its children.

Each bus is now an interconnect provider and an interconnect node as well
(cf. Documentation/interconnect/interconnect.rst), i.e. every bus registers
itself as a node. Node IDs are not hardcoded but rather assigned at
runtime, in probing order (subject to the above-mentioned exception
regarding relative order). This approach allows for using this driver with
various Exynos SoCs.

Frequencies requested via the interconnect API for a given node are
propagated to devfreq using dev_pm_qos_update_request(). Please note that
it is not an error when CONFIG_INTERCONNECT is 'n', in which case all
interconnect API functions are no-op.

Signed-off-by: Artur Świgoń <a.swigon@samsung.com>
---
 drivers/devfreq/exynos-bus.c | 144 +++++++++++++++++++++++++++++++++++
 1 file changed, 144 insertions(+)

diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
index 9fdb188915e8..694a9581dcdb 100644
--- a/drivers/devfreq/exynos-bus.c
+++ b/drivers/devfreq/exynos-bus.c
@@ -14,14 +14,19 @@
 #include <linux/devfreq-event.h>
 #include <linux/device.h>
 #include <linux/export.h>
+#include <linux/idr.h>
+#include <linux/interconnect-provider.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/pm_opp.h>
+#include <linux/pm_qos.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
 
 #define DEFAULT_SATURATION_RATIO	40
 
+#define kbps_to_khz(x) ((x) / 8)
+
 struct exynos_bus {
 	struct device *dev;
 
@@ -35,6 +40,12 @@ struct exynos_bus {
 	struct opp_table *opp_table;
 	struct clk *clk;
 	unsigned int ratio;
+
+	/* One provider per bus, one node per provider */
+	struct icc_provider provider;
+	struct icc_node *node;
+
+	struct dev_pm_qos_request qos_req;
 };
 
 /*
@@ -205,6 +216,39 @@ static void exynos_bus_passive_exit(struct device *dev)
 	clk_disable_unprepare(bus->clk);
 }
 
+static int exynos_bus_icc_set(struct icc_node *src, struct icc_node *dst)
+{
+	struct exynos_bus *src_bus = src->data, *dst_bus = dst->data;
+	s32 src_freq = kbps_to_khz(src->avg_bw);
+	s32 dst_freq = kbps_to_khz(dst->avg_bw);
+	int ret;
+
+	ret = dev_pm_qos_update_request(&src_bus->qos_req, src_freq);
+	if (ret < 0) {
+		dev_err(src_bus->dev, "failed to update PM QoS request");
+		return ret;
+	}
+
+	ret = dev_pm_qos_update_request(&dst_bus->qos_req, dst_freq);
+	if (ret < 0) {
+		dev_err(dst_bus->dev, "failed to update PM QoS request");
+		return ret;
+	}
+
+	return 0;
+}
+
+static struct icc_node *exynos_bus_icc_xlate(struct of_phandle_args *spec,
+					     void *data)
+{
+	struct exynos_bus *bus = data;
+
+	if (spec->np != bus->dev->of_node)
+		return ERR_PTR(-EINVAL);
+
+	return bus->node;
+}
+
 static int exynos_bus_parent_parse_of(struct device_node *np,
 					struct exynos_bus *bus)
 {
@@ -419,6 +463,96 @@ static int exynos_bus_profile_init_passive(struct exynos_bus *bus,
 	return 0;
 }
 
+static struct icc_node *exynos_bus_icc_get_parent(struct exynos_bus *bus)
+{
+	struct device_node *np = bus->dev->of_node;
+	struct of_phandle_args args;
+	int num, ret;
+
+	num = of_count_phandle_with_args(np, "exynos,interconnect-parent-node",
+					"#interconnect-cells");
+	if (num != 1)
+		return NULL; /* parent nodes are optional */
+
+	ret = of_parse_phandle_with_args(np, "exynos,interconnect-parent-node",
+					"#interconnect-cells", 0, &args);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	of_node_put(args.np);
+
+	return of_icc_get_from_provider(&args);
+}
+
+static int exynos_bus_icc_init(struct exynos_bus *bus)
+{
+	static DEFINE_IDA(ida);
+
+	struct device *dev = bus->dev;
+	struct icc_provider *provider = &bus->provider;
+	struct icc_node *node, *parent_node;
+	int id, ret;
+
+	/* Initialize the interconnect provider */
+	provider->set = exynos_bus_icc_set;
+	provider->aggregate = icc_std_aggregate;
+	provider->xlate = exynos_bus_icc_xlate;
+	provider->dev = dev;
+	provider->inter_set = true;
+	provider->data = bus;
+
+	ret = icc_provider_add(provider);
+	if (ret < 0)
+		return ret;
+
+	ret = id = ida_alloc(&ida, GFP_KERNEL);
+	if (ret < 0)
+		goto err_id;
+
+	node = icc_node_create(id);
+	if (IS_ERR(node)) {
+		ret = PTR_ERR(node);
+		goto err_node;
+	}
+
+	bus->node = node;
+	node->name = dev->of_node->name;
+	node->data = bus;
+	icc_node_add(node, provider);
+
+	parent_node = exynos_bus_icc_get_parent(bus);
+	if (IS_ERR(parent_node)) {
+		ret = PTR_ERR(parent_node);
+		goto err_parent;
+	}
+
+	if (parent_node) {
+		ret = icc_link_create(node, parent_node->id);
+		if (ret < 0)
+			goto err_parent;
+	}
+
+	ret = dev_pm_qos_add_request(bus->devfreq->dev.parent, &bus->qos_req,
+					DEV_PM_QOS_MIN_FREQUENCY, 0);
+	if (ret < 0)
+		goto err_request;
+
+	return 0;
+
+err_request:
+	if (parent_node)
+		icc_link_destroy(node, parent_node);
+err_parent:
+	icc_node_del(node);
+	icc_node_destroy(id);
+err_node:
+	ida_free(&ida, id);
+err_id:
+	icc_provider_del(provider);
+
+	return ret;
+}
+
 static int exynos_bus_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -468,6 +602,16 @@ static int exynos_bus_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto err;
 
+	/*
+	 * Initialize interconnect provider. A return value of -ENOTSUPP means
+	 * that CONFIG_INTERCONNECT is disabled.
+	 */
+	ret = exynos_bus_icc_init(bus);
+	if (ret < 0 && ret != -ENOTSUPP) {
+		dev_err(dev, "failed to initialize the interconnect provider");
+		goto err;
+	}
+
 	max_state = bus->devfreq->profile->max_state;
 	min_freq = (bus->devfreq->profile->freq_table[0] / 1000);
 	max_freq = (bus->devfreq->profile->freq_table[max_state - 1] / 1000);
-- 
2.17.1