[RFC PATCH v2 09/11] devfreq: exynos-bus: Add interconnect functionality to exynos-bus

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

From: Artur Świgoń <a.swigon@partner.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 most of
its edges are taken from the devfreq parent-child hierarchy (cf.
Documentation/devicetree/bindings/devfreq/exynos-bus.txt). Due to
unspecified relative probing order, -EPROBE_DEFER may be propagated to
guarantee that a child is probed before its parent.

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@partner.samsung.com>
---
 drivers/devfreq/exynos-bus.c | 153 +++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)

diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
index 8d44810cac69..e0232202720d 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 icc_units_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;
 };
 
 /*
@@ -59,6 +70,13 @@ exynos_bus_ops_edev(enable_edev);
 exynos_bus_ops_edev(disable_edev);
 exynos_bus_ops_edev(set_event);
 
+static int exynos_bus_next_id(void)
+{
+	static DEFINE_IDA(exynos_bus_icc_ida);
+
+	return ida_alloc(&exynos_bus_icc_ida, GFP_KERNEL);
+}
+
 static int exynos_bus_get_event(struct exynos_bus *bus,
 				struct devfreq_event_data *edata)
 {
@@ -171,6 +189,38 @@ 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 = icc_units_to_khz(src->avg_bw);
+	s32 dst_freq = icc_units_to_khz(dst->avg_bw);
+
+	dev_pm_qos_update_request(&src_bus->qos_req, src_freq);
+	dev_pm_qos_update_request(&dst_bus->qos_req, dst_freq);
+
+	return 0;
+}
+
+static int exynos_bus_icc_aggregate(struct icc_node *node, u32 tag, u32 avg_bw,
+				    u32 peak_bw, u32 *agg_avg, u32 *agg_peak)
+{
+	*agg_avg += avg_bw;
+	*agg_peak = max(*agg_peak, peak_bw);
+
+	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)
 {
@@ -366,6 +416,101 @@ static int exynos_bus_profile_init_passive(struct exynos_bus *bus,
 	return 0;
 }
 
+static int exynos_bus_icc_connect(struct exynos_bus *bus)
+{
+	struct device_node *np = bus->dev->of_node;
+	struct devfreq *parent_devfreq;
+	struct icc_node *parent_node = NULL;
+	struct of_phandle_args args;
+	int ret = 0;
+
+	parent_devfreq = devfreq_get_devfreq_by_phandle(bus->dev, 0);
+	if (!IS_ERR(parent_devfreq)) {
+		struct exynos_bus *parent_bus;
+
+		parent_bus = dev_get_drvdata(parent_devfreq->dev.parent);
+		parent_node = parent_bus->node;
+	} else {
+		/* Look for parent in DT */
+		int num = of_count_phandle_with_args(np, "parent",
+						     "#interconnect-cells");
+		if (num != 1)
+			goto out; /* 'parent' is optional */
+
+		ret = of_parse_phandle_with_args(np, "parent",
+						 "#interconnect-cells",
+						 0, &args);
+		if (ret < 0)
+			goto out;
+
+		of_node_put(args.np);
+
+		parent_node = of_icc_get_from_provider(&args);
+		if (IS_ERR(parent_node)) {
+			/* May be -EPROBE_DEFER */
+			ret = PTR_ERR(parent_node);
+			goto out;
+		}
+	}
+
+	ret = icc_link_create(bus->node, parent_node->id);
+
+out:
+	return ret;
+}
+
+static int exynos_bus_icc_init(struct exynos_bus *bus)
+{
+	struct device *dev = bus->dev;
+	struct icc_provider *provider = &bus->provider;
+	struct icc_node *node;
+	int id, ret;
+
+	/* Initialize the interconnect provider */
+	provider->set = exynos_bus_icc_set;
+	provider->aggregate = exynos_bus_icc_aggregate;
+	provider->xlate = exynos_bus_icc_xlate;
+	provider->dev = dev;
+	provider->data = bus;
+
+	ret = icc_provider_add(provider);
+	if (ret < 0)
+		goto out;
+
+	ret = id = exynos_bus_next_id();
+	if (ret < 0)
+		goto err_node;
+
+	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);
+
+	ret = exynos_bus_icc_connect(bus);
+	if (ret < 0)
+		goto err_connect;
+
+	ret = dev_pm_qos_add_request(bus->devfreq->dev.parent, &bus->qos_req,
+				     DEV_PM_QOS_MIN_FREQUENCY, 0);
+
+out:
+	return ret;
+
+err_connect:
+	icc_node_del(node);
+	icc_node_destroy(id);
+err_node:
+	icc_provider_del(provider);
+
+	return ret;
+}
+
 static int exynos_bus_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -415,6 +560,14 @@ 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)
+		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


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