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Subject[RFC PATCH v5 2/6] interconnect: Add generic interconnect driver for Exynos SoCs
Date
This patch adds a generic interconnect driver for Exynos SoCs in order
to provide interconnect functionality for each "samsung,exynos-bus"
compatible device.

The SoC topology is a graph (or more specifically, a tree) and its
edges are specified using the 'samsung,interconnect-parent' 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 dynamically at runtime. 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>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>

Changes for v5:
- adjust to renamed exynos,interconnect-parent-node property,
- use automatically generated platform device id as the interconect
node id instead of a now unavailable devfreq->id field,
- add icc_ prefix to some variables to make the code more self-commenting,
- use icc_nodes_remove() instead of icc_node_del() + icc_node_destroy(),
- adjust to exynos,interconnect-parent-node property rename to
samsung,interconnect-parent,
- converted to a separate platform driver in drivers/interconnect.
---
drivers/interconnect/Kconfig | 1 +
drivers/interconnect/Makefile | 1 +
drivers/interconnect/exynos/Kconfig | 6 ++
drivers/interconnect/exynos/Makefile | 4 +
drivers/interconnect/exynos/exynos.c | 185 +++++++++++++++++++++++++++++++++++
5 files changed, 197 insertions(+)
create mode 100644 drivers/interconnect/exynos/Kconfig
create mode 100644 drivers/interconnect/exynos/Makefile
create mode 100644 drivers/interconnect/exynos/exynos.c

diff --git a/drivers/interconnect/Kconfig b/drivers/interconnect/Kconfig
index 5b7204e..eca6eda 100644
--- a/drivers/interconnect/Kconfig
+++ b/drivers/interconnect/Kconfig
@@ -11,6 +11,7 @@ menuconfig INTERCONNECT

if INTERCONNECT

+source "drivers/interconnect/exynos/Kconfig"
source "drivers/interconnect/imx/Kconfig"
source "drivers/interconnect/qcom/Kconfig"

diff --git a/drivers/interconnect/Makefile b/drivers/interconnect/Makefile
index 4825c28..2ba1de6 100644
--- a/drivers/interconnect/Makefile
+++ b/drivers/interconnect/Makefile
@@ -4,5 +4,6 @@ CFLAGS_core.o := -I$(src)
icc-core-objs := core.o

obj-$(CONFIG_INTERCONNECT) += icc-core.o
+obj-$(CONFIG_INTERCONNECT_EXYNOS) += exynos/
obj-$(CONFIG_INTERCONNECT_IMX) += imx/
obj-$(CONFIG_INTERCONNECT_QCOM) += qcom/
diff --git a/drivers/interconnect/exynos/Kconfig b/drivers/interconnect/exynos/Kconfig
new file mode 100644
index 0000000..e51e52e
--- /dev/null
+++ b/drivers/interconnect/exynos/Kconfig
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config INTERCONNECT_EXYNOS
+ tristate "Exynos generic interconnect driver"
+ depends on ARCH_EXYNOS || COMPILE_TEST
+ help
+ Generic interconnect driver for Exynos SoCs.
diff --git a/drivers/interconnect/exynos/Makefile b/drivers/interconnect/exynos/Makefile
new file mode 100644
index 0000000..e19d1df
--- /dev/null
+++ b/drivers/interconnect/exynos/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+exynos-interconnect-objs := exynos.o
+
+obj-$(CONFIG_INTERCONNECT_EXYNOS) += exynos-interconnect.o
diff --git a/drivers/interconnect/exynos/exynos.c b/drivers/interconnect/exynos/exynos.c
new file mode 100644
index 0000000..8278194
--- /dev/null
+++ b/drivers/interconnect/exynos/exynos.c
@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Exynos generic interconnect provider driver
+ *
+ * Copyright (c) 2020 Samsung Electronics Co., Ltd.
+ *
+ * Authors: Artur Świgoń <a.swigon@samsung.com>
+ * Sylwester Nawrocki <s.nawrocki@samsung.com>
+ */
+#include <linux/device.h>
+#include <linux/interconnect-provider.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm_qos.h>
+
+#define kbps_to_khz(x) ((x) / 8)
+
+struct exynos_icc_priv {
+ struct device *dev;
+
+ /* One interconnect node per provider */
+ struct icc_provider provider;
+ struct icc_node *node;
+
+ struct dev_pm_qos_request qos_req;
+};
+
+static struct icc_node *exynos_icc_get_parent(struct device_node *np)
+{
+ struct of_phandle_args args;
+ int num, ret;
+
+ num = of_count_phandle_with_args(np, "samsung,interconnect-parent",
+ "#interconnect-cells");
+ if (num != 1)
+ return NULL; /* parent nodes are optional */
+
+ ret = of_parse_phandle_with_args(np, "samsung,interconnect-parent",
+ "#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_generic_icc_set(struct icc_node *src, struct icc_node *dst)
+{
+ struct exynos_icc_priv *src_priv = src->data, *dst_priv = dst->data;
+ s32 src_freq = kbps_to_khz(max(src->avg_bw, src->peak_bw));
+ s32 dst_freq = kbps_to_khz(max(dst->avg_bw, dst->peak_bw));
+ int ret;
+
+ ret = dev_pm_qos_update_request(&src_priv->qos_req, src_freq);
+ if (ret < 0) {
+ dev_err(src_priv->dev, "failed to update PM QoS of %s\n",
+ src->name);
+ return ret;
+ }
+
+ ret = dev_pm_qos_update_request(&dst_priv->qos_req, dst_freq);
+ if (ret < 0) {
+ dev_err(dst_priv->dev, "failed to update PM QoS of %s\n",
+ dst->name);
+ return ret;
+ }
+
+ return 0;
+}
+
+static struct icc_node *exynos_generic_icc_xlate(struct of_phandle_args *spec,
+ void *data)
+{
+ struct exynos_icc_priv *priv = data;
+
+ if (spec->np != priv->dev->parent->of_node)
+ return ERR_PTR(-EINVAL);
+
+ return priv->node;
+}
+
+static int exynos_generic_icc_remove(struct platform_device *pdev)
+{
+ struct exynos_icc_priv *priv = platform_get_drvdata(pdev);
+ struct icc_node *parent_node, *node = priv->node;
+
+ parent_node = exynos_icc_get_parent(priv->dev->parent->of_node);
+ if (parent_node && !IS_ERR(parent_node))
+ icc_link_destroy(node, parent_node);
+
+ icc_nodes_remove(&priv->provider);
+ icc_provider_del(&priv->provider);
+
+ return 0;
+}
+
+static int exynos_generic_icc_probe(struct platform_device *pdev)
+{
+ struct device *bus_dev = pdev->dev.parent;
+ struct exynos_icc_priv *priv;
+ struct icc_provider *provider;
+ struct icc_node *icc_node, *icc_parent_node;
+ int ret;
+
+ priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->dev = &pdev->dev;
+ platform_set_drvdata(pdev, priv);
+
+ provider = &priv->provider;
+
+ provider->set = exynos_generic_icc_set;
+ provider->aggregate = icc_std_aggregate;
+ provider->xlate = exynos_generic_icc_xlate;
+ provider->dev = bus_dev;
+ provider->inter_set = true;
+ provider->data = priv;
+
+ ret = icc_provider_add(provider);
+ if (ret < 0)
+ return ret;
+
+ icc_node = icc_node_create(pdev->id);
+ if (IS_ERR(icc_node)) {
+ ret = PTR_ERR(icc_node);
+ goto err_prov_del;
+ }
+
+ priv->node = icc_node;
+ icc_node->name = bus_dev->of_node->name;
+ icc_node->data = priv;
+ icc_node_add(icc_node, provider);
+
+ icc_parent_node = exynos_icc_get_parent(bus_dev->of_node);
+ if (IS_ERR(icc_parent_node)) {
+ ret = PTR_ERR(icc_parent_node);
+ goto err_node_del;
+ }
+ if (icc_parent_node) {
+ ret = icc_link_create(icc_node, icc_parent_node->id);
+ if (ret < 0)
+ goto err_node_del;
+ }
+
+ /*
+ * Register a PM QoS request for the bus device for which also devfreq
+ * functionality is registered.
+ */
+ ret = dev_pm_qos_add_request(bus_dev, &priv->qos_req,
+ DEV_PM_QOS_MIN_FREQUENCY, 0);
+ if (ret < 0)
+ goto err_link_destroy;
+
+ return 0;
+
+err_link_destroy:
+ if (icc_parent_node)
+ icc_link_destroy(icc_node, icc_parent_node);
+err_node_del:
+ icc_nodes_remove(provider);
+err_prov_del:
+ icc_provider_del(provider);
+
+ return ret;
+}
+
+static struct platform_driver exynos_generic_icc_driver = {
+ .driver = {
+ .name = "exynos-generic-icc",
+ },
+ .probe = exynos_generic_icc_probe,
+ .remove = exynos_generic_icc_remove,
+};
+module_platform_driver(exynos_generic_icc_driver);
+
+MODULE_DESCRIPTION("Exynos generic interconnect driver");
+MODULE_AUTHOR("Artur Świgoń <a.swigon@samsung.com>");
+MODULE_AUTHOR("Sylwester Nawrocki <s.nawrocki@samsung.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:exynos-generic-icc");
--
2.7.4
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