[PATCH RFC 5/9] PM / devfreq: Add devfreq driver for interconnect bandwidth voting

[Sibi Sankar]

From: Saravana Kannan <skannan@xxxxxxxxxxxxxx>

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 powersave governor to set the GPU to DDR
  interconnect path for minimum performance.
* Use the Passive governor to scale the DDR frequency based
  on the needs of the CPUs' current frequency

Signed-off-by: Saravana Kannan <skannan@xxxxxxxxxxxxxx>
[Sibi: cleanup and added passive governor support]
Signed-off-by: Sibi Sankar <sibis@xxxxxxxxxxxxxx>
---
 drivers/devfreq/Kconfig        |  15 ++++
 drivers/devfreq/Makefile       |   1 +
 drivers/devfreq/devfreq_icbw.c | 132 +++++++++++++++++++++++++++++++++
 3 files changed, 148 insertions(+)
 create mode 100644 drivers/devfreq/devfreq_icbw.c

diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
index 9a45f464a56b..0df5b65f157a 100644
--- a/drivers/devfreq/Kconfig
+++ b/drivers/devfreq/Kconfig
@@ -117,6 +117,21 @@ config ARM_RK3399_DMC_DEVFREQ
           It sets the frequency for the memory controller and reads the usage counts
           from hardware.
 
+config DEVFREQ_ICBW
+	tristate "Driver for making bandwidth votes on interconnect paths"
+	select DEVFREQ_GOV_PASSIVE
+	select DEVFREQ_GOV_PERFORMANCE
+	select DEVFREQ_GOV_POWERSAVE
+	select DEVFREQ_GOV_USERSPACE
+	depends on INTERCONNECT
+	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 32b8d4d3f12c..66591b0e5259 100644
--- a/drivers/devfreq/Makefile
+++ b/drivers/devfreq/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
 obj-$(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 000000000000..c552cf4218c8
--- /dev/null
+++ b/drivers/devfreq/devfreq_icbw.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2018, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/devfreq.h>
+#include <linux/interconnect.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct icbw_data {
+	struct devfreq *df;
+	struct icc_path *path;
+	u32 cur_ab;
+	u32 cur_pb;
+};
+
+static int icbw_target(struct device *dev, unsigned long *freq, u32 flags)
+{
+	struct dev_pm_opp *opp;
+	struct icbw_data *data = dev_get_drvdata(dev);
+	u32 new_pb, new_ab;
+	int ret;
+
+	opp = devfreq_recommended_opp(dev, freq, flags);
+	if (IS_ERR(opp))
+		return PTR_ERR(opp);
+
+	/* Get avg and peak bandwidth */
+	new_ab = dev_pm_opp_get_avg_bw(opp);
+	new_pb = dev_pm_opp_get_peak_bw(opp);
+	dev_pm_opp_put(opp);
+
+	if (data->cur_pb == new_pb && data->cur_ab == new_ab)
+		return 0;
+
+	dev_dbg(dev, "BW icc: AB: %u PB: %u\n", new_ab, new_pb);
+
+	ret = icc_set_bw(data->path, new_ab, new_pb);
+	if (ret) {
+		dev_err(dev, "bandwidth request failed (%d)\n", ret);
+	} else {
+		data->cur_pb = new_pb;
+		data->cur_ab = new_ab;
+	}
+
+	return ret;
+}
+
+static int devfreq_icbw_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct devfreq_dev_profile *profile;
+	struct devfreq_passive_data *passive_data;
+	struct icbw_data *data;
+	int ret;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+	dev_set_drvdata(dev, data);
+
+	passive_data = devm_kzalloc(dev, sizeof(*passive_data), GFP_KERNEL);
+	if (!passive_data)
+		return -ENOMEM;
+
+	passive_data->cpufreq_type = true;
+
+	profile = devm_kzalloc(dev, sizeof(*profile), GFP_KERNEL);
+	if (!profile)
+		return -ENOMEM;
+
+	profile->target = icbw_target;
+
+	data->path = of_icc_get(dev, NULL);
+	if (IS_ERR(data->path)) {
+		dev_err(dev, "Unable to register interconnect path\n");
+		return PTR_ERR(data->path);
+	}
+
+	ret = dev_pm_opp_of_add_table(dev);
+	if (ret) {
+		dev_err(dev, "Couldn't find OPP table\n");
+		goto err_icc;
+	}
+
+	data->df = devfreq_add_device(dev, profile,
+				      DEVFREQ_GOV_PASSIVE, passive_data);
+	if (IS_ERR(data->df)) {
+		ret = PTR_ERR(data->df);
+		goto err_opp_table;
+	}
+
+	return 0;
+
+err_opp_table:
+	dev_pm_opp_of_remove_table(dev);
+err_icc:
+	icc_put(data->path);
+	return ret;
+}
+
+static int devfreq_icbw_remove(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct icbw_data *data = dev_get_drvdata(dev);
+
+	devfreq_remove_device(data->df);
+	icc_put(data->path);
+	return 0;
+}
+
+static const struct of_device_id icbw_match_table[] = {
+	{ .compatible = "devfreq-icbw" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, icbw_match_table);
+
+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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