[PATCH V8 4/8] devfreq: add mediatek cci devfreq

[Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>]

From: "Andrew-sh.Cheng" <andrew-sh.cheng@mediatek.com>

This adds a devfreq driver for the Cache Coherent Interconnect (CCI)
of the Mediatek MT8183.

On the MT8183 the CCI is supplied by the same regulator as the LITTLE
cores. The driver is notified when the regulator voltage changes
(driven by cpufreq) and adjusts the CCI frequency to the maximum
possible value.

Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>
---
 drivers/devfreq/Kconfig              |  10 ++
 drivers/devfreq/Makefile             |   1 +
 drivers/devfreq/mt8183-cci-devfreq.c | 198 +++++++++++++++++++++++++++++++++++
 3 files changed, 209 insertions(+)
 create mode 100644 drivers/devfreq/mt8183-cci-devfreq.c

diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
index f56132b0ae64..2538255ac2c1 100644
--- a/drivers/devfreq/Kconfig
+++ b/drivers/devfreq/Kconfig
@@ -111,6 +111,16 @@ config ARM_IMX8M_DDRC_DEVFREQ
 	  This adds the DEVFREQ driver for the i.MX8M DDR Controller. It allows
 	  adjusting DRAM frequency.
 
+config ARM_MT8183_CCI_DEVFREQ
+	tristate "MT8183 CCI DEVFREQ Driver"
+	depends on ARM_MEDIATEK_CPUFREQ
+	help
+		This adds a devfreq driver for Cache Coherent Interconnect
+		of Mediatek MT8183, which is shared the same regulator
+		with cpu cluster.
+		It can track buck voltage and update a proper CCI frequency.
+		Use notification to get regulator status.
+
 config ARM_TEGRA_DEVFREQ
 	tristate "NVIDIA Tegra30/114/124/210 DEVFREQ Driver"
 	depends on ARCH_TEGRA_3x_SOC || ARCH_TEGRA_114_SOC || \
diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
index a16333ea7034..991ef7740759 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-$(CONFIG_ARM_IMX_BUS_DEVFREQ)	+= imx-bus.o
 obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)	+= imx8m-ddrc.o
+obj-$(CONFIG_ARM_MT8183_CCI_DEVFREQ)	+= mt8183-cci-devfreq.o
 obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
 obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra30-devfreq.o
 
diff --git a/drivers/devfreq/mt8183-cci-devfreq.c b/drivers/devfreq/mt8183-cci-devfreq.c
new file mode 100644
index 000000000000..018543db7bae
--- /dev/null
+++ b/drivers/devfreq/mt8183-cci-devfreq.c
@@ -0,0 +1,198 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021 MediaTek Inc.
+
+ * Author: Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/devfreq.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/time.h>
+
+#define MAX_VOLT_LIMIT		(1150000)
+
+struct cci_devfreq {
+	struct devfreq *devfreq;
+	struct regulator *cpu_reg;
+	struct clk *cci_clk;
+	int old_vproc;
+	unsigned long old_freq;
+};
+
+static int mtk_cci_set_voltage(struct cci_devfreq *cci_df, int vproc)
+{
+	int ret;
+
+	ret = regulator_set_voltage(cci_df->cpu_reg, vproc,
+				    MAX_VOLT_LIMIT);
+	if (!ret)
+		cci_df->old_vproc = vproc;
+	return ret;
+}
+
+static int mtk_cci_devfreq_target(struct device *dev, unsigned long *freq,
+				  u32 flags)
+{
+	int ret;
+	struct cci_devfreq *cci_df = dev_get_drvdata(dev);
+	struct dev_pm_opp *opp;
+	unsigned long opp_rate, opp_voltage, old_voltage;
+
+	if (!cci_df)
+		return -EINVAL;
+
+	if (cci_df->old_freq == *freq)
+		return 0;
+
+	opp_rate = *freq;
+	opp = devfreq_recommended_opp(dev, &opp_rate, 1);
+	opp_voltage = dev_pm_opp_get_voltage(opp);
+	dev_pm_opp_put(opp);
+
+	old_voltage = cci_df->old_vproc;
+	if (old_voltage == 0)
+		old_voltage = regulator_get_voltage(cci_df->cpu_reg);
+
+	// scale up: set voltage first then freq
+	if (opp_voltage > old_voltage) {
+		ret = mtk_cci_set_voltage(cci_df, opp_voltage);
+		if (ret) {
+			pr_err("cci: failed to scale up voltage\n");
+			return ret;
+		}
+	}
+
+	ret = clk_set_rate(cci_df->cci_clk, *freq);
+	if (ret) {
+		pr_err("%s: failed cci to set rate: %d\n", __func__,
+		       ret);
+		mtk_cci_set_voltage(cci_df, old_voltage);
+		return ret;
+	}
+
+	// scale down: set freq first then voltage
+	if (opp_voltage < old_voltage) {
+		ret = mtk_cci_set_voltage(cci_df, opp_voltage);
+		if (ret) {
+			pr_err("cci: failed to scale down voltage\n");
+			clk_set_rate(cci_df->cci_clk, cci_df->old_freq);
+			return ret;
+		}
+	}
+
+	cci_df->old_freq = *freq;
+
+	return 0;
+}
+
+static struct devfreq_dev_profile cci_devfreq_profile = {
+	.target = mtk_cci_devfreq_target,
+};
+
+static int mtk_cci_devfreq_probe(struct platform_device *pdev)
+{
+	struct device *cci_dev = &pdev->dev;
+	struct cci_devfreq *cci_df;
+	struct devfreq_passive_data *passive_data;
+	int ret;
+
+	cci_df = devm_kzalloc(cci_dev, sizeof(*cci_df), GFP_KERNEL);
+	if (!cci_df)
+		return -ENOMEM;
+
+	cci_df->cci_clk = devm_clk_get(cci_dev, "cci_clock");
+	ret = PTR_ERR_OR_ZERO(cci_df->cci_clk);
+	if (ret) {
+		if (ret != -EPROBE_DEFER)
+			dev_err(cci_dev, "failed to get clock for CCI: %d\n",
+				ret);
+		return ret;
+	}
+	cci_df->cpu_reg = devm_regulator_get_optional(cci_dev, "proc");
+	ret = PTR_ERR_OR_ZERO(cci_df->cpu_reg);
+	if (ret) {
+		if (ret != -EPROBE_DEFER)
+			dev_err(cci_dev, "failed to get regulator for CCI: %d\n",
+				ret);
+		return ret;
+	}
+	ret = regulator_enable(cci_df->cpu_reg);
+	if (ret) {
+		dev_err(cci_dev, "enable buck for cci fail\n");
+		return ret;
+	}
+
+	ret = dev_pm_opp_of_add_table(cci_dev);
+	if (ret) {
+		dev_err(cci_dev, "Fail to get OPP table for CCI: %d\n", ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, cci_df);
+
+	passive_data = devm_kzalloc(cci_dev, sizeof(*passive_data), GFP_KERNEL);
+	if (!passive_data) {
+		ret = -ENOMEM;
+		goto err_opp;
+	}
+
+	passive_data->parent_type = CPUFREQ_PARENT_DEV;
+
+	cci_df->devfreq = devm_devfreq_add_device(cci_dev,
+						  &cci_devfreq_profile,
+						  DEVFREQ_GOV_PASSIVE,
+						  passive_data);
+	if (IS_ERR(cci_df->devfreq)) {
+		ret = PTR_ERR(cci_df->devfreq);
+		dev_err(cci_dev, "cannot create cci devfreq device:%d\n", ret);
+		goto err_opp;
+	}
+
+	return 0;
+
+err_opp:
+	dev_pm_opp_of_remove_table(cci_dev);
+	return ret;
+}
+
+static int mtk_cci_devfreq_remove(struct platform_device *pdev)
+{
+	struct device *cci_dev = &pdev->dev;
+	struct cci_devfreq *cci_df;
+	struct notifier_block *opp_nb;
+
+	cci_df = platform_get_drvdata(pdev);
+	opp_nb = &cci_df->opp_nb;
+
+	dev_pm_opp_unregister_notifier(cci_dev, opp_nb);
+	dev_pm_opp_of_remove_table(cci_dev);
+	regulator_disable(cci_df->cpu_reg);
+
+	return 0;
+}
+
+static const __maybe_unused struct of_device_id
+	mediatek_cci_of_match[] = {
+	{ .compatible = "mediatek,mt8183-cci" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, mediatek_cci_of_match);
+
+static struct platform_driver cci_devfreq_driver = {
+	.probe	= mtk_cci_devfreq_probe,
+	.remove	= mtk_cci_devfreq_remove,
+	.driver = {
+		.name = "mediatek-cci-devfreq",
+		.of_match_table = of_match_ptr(mediatek_cci_of_match),
+	},
+};
+
+module_platform_driver(cci_devfreq_driver);
+
+MODULE_DESCRIPTION("Mediatek CCI devfreq driver");
+MODULE_AUTHOR("Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>");
+MODULE_LICENSE("GPL v2");
-- 
2.12.5
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