[PATCH v3 2/2] PM / devfreq: Add devfreq driver for interconnect bandwidth voting

[Saravana Kannan]

This driver registers itself as a devfreq device that allows devfreq
governors to make bandwidth votes for an interconnect path. This allows
applying various policies for different interconnect paths using devfreq
governors.

Example uses:
* Use the devfreq performance governor to set the CPU to DDR interconnect
  path for maximum performance.
* Use the devfreq performance governor to set the GPU to DDR interconnect
  path for maximum performance.
* Use the CPU frequency to device frequency mapping governor to scale the
  DDR frequency based on the needs of the CPUs' current frequency.

Signed-off-by: Saravana Kannan <skannan@xxxxxxxxxxxxxx>
---
 Documentation/devicetree/bindings/devfreq/icbw.txt |  21 ++++
 drivers/devfreq/Kconfig                            |  13 +++
 drivers/devfreq/Makefile                           |   1 +
 drivers/devfreq/devfreq_icbw.c                     | 116 +++++++++++++++++++++
 4 files changed, 151 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/devfreq/icbw.txt
 create mode 100644 drivers/devfreq/devfreq_icbw.c

diff --git a/Documentation/devicetree/bindings/devfreq/icbw.txt b/Documentation/devicetree/bindings/devfreq/icbw.txt
new file mode 100644
index 0000000..36cf045
--- /dev/null
+++ b/Documentation/devicetree/bindings/devfreq/icbw.txt
@@ -0,0 +1,21 @@
+Interconnect bandwidth device
+
+icbw is a device that represents an interconnect path that connects two
+devices. This device is typically used to vote for BW requirements between
+two devices. Eg: CPU to DDR, GPU to DDR, etc
+
+Required properties:
+- compatible:		Must be "devfreq-icbw"
+- interconnects:	Pairs of phandles and interconnect provider specifier
+			to denote the edge source and destination ports of
+			the interconnect path. See also:
+		Documentation/devicetree/bindings/interconnect/interconnect.txt
+- interconnect-names:	Must have one entry with the name "path".
+
+Example:
+
+	qcom,cpubw {
+		compatible = "devfreq-icbw";
+		interconnects = <&snoc MASTER_APSS_1 &bimc SLAVE_EBI_CH0>;
+		interconnect-names = "path";
+	};
diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
index 3d9ae68..590370e 100644
--- a/drivers/devfreq/Kconfig
+++ b/drivers/devfreq/Kconfig
@@ -121,6 +121,19 @@ config ARM_RK3399_DMC_DEVFREQ
           It sets the frequency for the memory controller and reads the usage counts
           from hardware.
 
+config DEVFREQ_ICBW
+	bool "DEVFREQ device for making bandwidth votes on interconnect paths"
+	select DEVFREQ_GOV_PERFORMANCE
+	select DEVFREQ_GOV_POWERSAVE
+	select DEVFREQ_GOV_USERSPACE
+	default n
+	help
+	  Different devfreq governors use this devfreq device to make
+	  bandwidth votes for interconnect paths between different devices
+	  (Eg: CPU to DDR, GPU to DDR, etc). This driver provides a generic
+	  interface so that the devfreq governors can be shared across SoCs
+	  and architectures.
+
 source "drivers/devfreq/event/Kconfig"
 
 endif # PM_DEVFREQ
diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
index e9dc3e9..b302c5cf 100644
--- a/drivers/devfreq/Makefile
+++ b/drivers/devfreq/Makefile
@@ -12,6 +12,7 @@ obj-$(CONFIG_DEVFREQ_GOV_CPUFREQ_MAP)	+= governor_cpufreq_map.o
 obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
 obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
 obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra-devfreq.o
+obj-$(CONFIG_DEVFREQ_ICBW)		+= devfreq_icbw.o
 
 # DEVFREQ Event Drivers
 obj-$(CONFIG_PM_DEVFREQ_EVENT)		+= event/
diff --git a/drivers/devfreq/devfreq_icbw.c b/drivers/devfreq/devfreq_icbw.c
new file mode 100644
index 0000000..231fb21
--- /dev/null
+++ b/drivers/devfreq/devfreq_icbw.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2013-2014, 2018, The Linux Foundation. All rights reserved.
+ */
+
+#define pr_fmt(fmt) "icbw: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/mutex.h>
+#include <linux/devfreq.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/interconnect.h>
+
+struct dev_data {
+	struct icc_path *path;
+	u32 cur_ab;
+	u32 cur_pb;
+	unsigned long gov_ab;
+	struct devfreq *df;
+	struct devfreq_dev_profile dp;
+};
+
+static int icbw_target(struct device *dev, unsigned long *freq, u32 flags)
+{
+	struct dev_data *d = dev_get_drvdata(dev);
+	int ret;
+	u32 new_pb = *freq, new_ab = d->gov_ab;
+
+	if (d->cur_pb == new_pb && d->cur_ab == new_ab)
+		return 0;
+
+	dev_dbg(dev, "BW KBps: AB: %u PB: %u\n", new_ab, new_pb);
+
+	ret = icc_set(d->path, new_ab, new_pb);
+	if (ret) {
+		dev_err(dev, "bandwidth request failed (%d)\n", ret);
+	} else {
+		d->cur_pb = new_pb;
+		d->cur_ab = new_ab;
+	}
+
+	return ret;
+}
+
+static int icbw_get_dev_status(struct device *dev,
+				struct devfreq_dev_status *stat)
+{
+	struct dev_data *d = dev_get_drvdata(dev);
+
+	stat->private_data = &d->gov_ab;
+	return 0;
+}
+
+static int devfreq_icbw_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct dev_data *d;
+	struct devfreq_dev_profile *p;
+
+	d = devm_kzalloc(dev, sizeof(*d), GFP_KERNEL);
+	if (!d)
+		return -ENOMEM;
+	dev_set_drvdata(dev, d);
+
+	p = &d->dp;
+	p->polling_ms = 50;
+	p->target = icbw_target;
+	p->get_dev_status = icbw_get_dev_status;
+
+	d->path = of_icc_get(dev, "path");
+	if (IS_ERR(d->path)) {
+		dev_err(dev, "Unable to register interconnect path\n");
+		return -ENODEV;
+	}
+
+	d->df = devfreq_add_device(dev, p, "performance", NULL);
+	if (IS_ERR(d->df)) {
+		icc_put(d->path);
+		return PTR_ERR(d->df);
+	}
+
+	return 0;
+}
+
+static int devfreq_icbw_remove(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct dev_data *d = dev_get_drvdata(dev);
+
+	devfreq_remove_device(d->df);
+	icc_put(d->path);
+	return 0;
+}
+
+static const struct of_device_id icbw_match_table[] = {
+	{ .compatible = "devfreq-icbw" },
+	{}
+};
+
+static struct platform_driver icbw_driver = {
+	.probe = devfreq_icbw_probe,
+	.remove = devfreq_icbw_remove,
+	.driver = {
+		.name = "devfreq-icbw",
+		.of_match_table = icbw_match_table,
+	},
+};
+
+module_platform_driver(icbw_driver);
+MODULE_DESCRIPTION("Interconnect bandwidth voting driver");
+MODULE_LICENSE("GPL v2");
-- 
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