Re: [v5, PATCH 3/5] devfreq: add mediatek cci devfreq

[Chanwoo Choi <cw00.choi@samsung.com>]

Hi,

"mtk_cci_vmon" governor looks like the devfreq passive governor.
But, the existing devfreq passive governor depend on the other devfreq device.
"mtk_cci_vmon" governor depend on the regulator with regulator notifier.

I think that it is better to extend the passive governor
in order to support the regulator notifier.
It is possible because passive governor already used
the devfreq notifier. 

Previously, the patch[1] tried to add the cpu based scaling to passive governor.
[1] https://lore.kernel.org/patchwork/patch/1101049/
- [RFC,v2] PM / devfreq: Add cpu based scaling support to passive_governor

Regards,
Chanwoo Choi

On 11/26/19 8:50 PM, Andrew-sh.Cheng wrote:
> 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 | 247 +++++++++++++++++++++++++++++++++++
>  3 files changed, 258 insertions(+)
>  create mode 100644 drivers/devfreq/mt8183-cci-devfreq.c
> 
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index defe1d438710..76bc42657787 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -92,6 +92,16 @@ config ARM_EXYNOS_BUS_DEVFREQ
>  	  and adjusts the operating frequencies and voltages with OPP support.
>  	  This does not yet operate with optimal voltages.
>  
> +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 338ae8440db6..1fa05e39e4ff 100644
> --- a/drivers/devfreq/Makefile
> +++ b/drivers/devfreq/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
>  
>  # DEVFREQ Drivers
>  obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
> +obj-$(CONFIG_ARM_MT8183_CCI_DEVFREQ)	+= mt8183-cci-devfreq.o
>  obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>  obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra30-devfreq.o
>  obj-$(CONFIG_ARM_TEGRA20_DEVFREQ)	+= tegra20-devfreq.o
> diff --git a/drivers/devfreq/mt8183-cci-devfreq.c b/drivers/devfreq/mt8183-cci-devfreq.c
> new file mode 100644
> index 000000000000..818a167c442f
> --- /dev/null
> +++ b/drivers/devfreq/mt8183-cci-devfreq.c
> @@ -0,0 +1,247 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019 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 "governor.h"
> +
> +struct cci_devfreq {
> +	struct devfreq *devfreq;
> +	struct regulator *proc_reg;
> +	unsigned long proc_reg_uV;																																																																																															
> +	struct clk *cci_clk;
> +	struct notifier_block nb;
> +};
> +
> +static int cci_devfreq_regulator_notifier(struct notifier_block *nb,
> +					  unsigned long val, void *data)
> +{
> +	int ret;
> +	struct cci_devfreq *cci_df =
> +		container_of(nb, struct cci_devfreq, nb);
> +
> +	/* deal with reduce frequency */
> +	if (val & REGULATOR_EVENT_PRE_VOLTAGE_CHANGE) {
> +		struct pre_voltage_change_data *pvc_data = data;
> +
> +		if (pvc_data->min_uV < pvc_data->old_uV) {
> +			cci_df->proc_reg_uV =
> +				(unsigned long)(pvc_data->min_uV);
> +			mutex_lock(&cci_df->devfreq->lock);
> +			ret = update_devfreq(cci_df->devfreq);
> +			if (ret)
> +				pr_err("Fail to reduce cci frequency: %d\n",
> +				       ret);
> +			mutex_unlock(&cci_df->devfreq->lock);
> +		}
> +	} else if ((val & REGULATOR_EVENT_ABORT_VOLTAGE_CHANGE) &&
> +	    ((unsigned long)data > cci_df->proc_reg_uV)) {
> +		cci_df->proc_reg_uV = (unsigned long)data;
> +		mutex_lock(&cci_df->devfreq->lock);
> +		ret = update_devfreq(cci_df->devfreq);
> +		if (ret)
> +			pr_err("Fail to raise cci frequency back: %d\n", ret);
> +		mutex_unlock(&cci_df->devfreq->lock);
> +	} else if ((val & REGULATOR_EVENT_VOLTAGE_CHANGE) &&
> +	    (cci_df->proc_reg_uV < (unsigned long)data)) {
> +		/* deal with increase frequency */
> +		cci_df->proc_reg_uV = (unsigned long)data;
> +		mutex_lock(&cci_df->devfreq->lock);
> +		ret = update_devfreq(cci_df->devfreq);
> +		if (ret)
> +			pr_err("Fail to raise cci frequency: %d\n", ret);
> +		mutex_unlock(&cci_df->devfreq->lock);
> +	}
> +
> +	return 0;
> +}
> +
> +static int mtk_cci_governor_get_target(struct devfreq *devfreq,
> +				       unsigned long *freq)
> +{
> +	struct cci_devfreq *cci_df;
> +	struct dev_pm_opp *opp;
> +
> +	cci_df = dev_get_drvdata(devfreq->dev.parent);
> +
> +	/* find available frequency */
> +	opp = dev_pm_opp_find_freq_ceil_by_volt(devfreq->dev.parent,
> +						cci_df->proc_reg_uV);
> +	*freq = dev_pm_opp_get_freq(opp);
> +
> +	return 0;
> +}
> +
> +static int mtk_cci_governor_event_handler(struct devfreq *devfreq,
> +					  unsigned int event, void *data)
> +{
> +	int ret;
> +	struct cci_devfreq *cci_df;
> +	struct notifier_block *nb;
> +
> +	cci_df = dev_get_drvdata(devfreq->dev.parent);
> +	nb = &cci_df->nb;
> +
> +	switch (event) {
> +	case DEVFREQ_GOV_START:
> +	case DEVFREQ_GOV_RESUME:
> +		nb->notifier_call = cci_devfreq_regulator_notifier;
> +		ret = regulator_register_notifier(cci_df->proc_reg,
> +						  nb);
> +		if (ret)
> +			pr_err("%s: failed to add governor: %d\n", __func__,
> +			       ret);
> +		break;
> +
> +	case DEVFREQ_GOV_STOP:
> +	case DEVFREQ_GOV_SUSPEND:
> +		ret = regulator_unregister_notifier(cci_df->proc_reg,
> +						    nb);
> +		if (ret)
> +			pr_err("%s: failed to add governor: %d\n", __func__,
> +			       ret);
> +		break;
> +
> +	default:
> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +static struct devfreq_governor mtk_cci_devfreq_governor = {
> +	.name = "mtk_cci_vmon",
> +	.get_target_freq = mtk_cci_governor_get_target,
> +	.event_handler = mtk_cci_governor_event_handler,
> +	.immutable = true
> +};
> +
> +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);
> +
> +	if (!cci_df)
> +		return -EINVAL;
> +
> +	ret = clk_set_rate(cci_df->cci_clk, *freq);
> +	if (ret) {
> +		pr_err("%s: failed cci to set rate: %d\n", __func__,
> +		       ret);
> +		return ret;
> +	}
> +
> +	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;
> +	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->proc_reg = devm_regulator_get_optional(cci_dev, "proc");
> +	ret = PTR_ERR_OR_ZERO(cci_df->proc_reg);
> +	if (ret) {
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(cci_dev, "failed to get regulator for CCI: %d\n",
> +				ret);
> +		return ret;
> +	}
> +
> +	ret = dev_pm_opp_of_add_table(cci_dev);
> +	if (ret) {
> +		dev_err(cci_dev, "Fail to init CCI OPP table: %d\n", ret);
> +		return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, cci_df);
> +
> +	cci_df->devfreq = devm_devfreq_add_device(cci_dev,
> +						  &cci_devfreq_profile,
> +						  "mtk_cci_vmon",
> +						  NULL);
> +	if (IS_ERR(cci_df->devfreq)) {
> +		ret = PTR_ERR(cci_df->devfreq);
> +		dev_err(cci_dev, "cannot create cci devfreq device:%d\n", ret);
> +		dev_pm_opp_of_remove_table(cci_dev);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const __maybe_unused struct of_device_id
> +	mediatek_cci_devfreq_of_match[] = {
> +	{ .compatible = "mediatek,mt8183-cci" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, mediatek_cci_devfreq_of_match);
> +
> +static struct platform_driver cci_devfreq_driver = {
> +	.probe	= mtk_cci_devfreq_probe,
> +	.driver = {
> +		.name = "mediatek-cci-devfreq",
> +		.of_match_table = of_match_ptr(mediatek_cci_devfreq_of_match),
> +	},
> +};
> +
> +static int __init mtk_cci_devfreq_init(void)
> +{
> +	int ret;
> +
> +	ret = devfreq_add_governor(&mtk_cci_devfreq_governor);
> +	if (ret) {
> +		pr_err("%s: failed to add governor: %d\n", __func__, ret);
> +		return ret;
> +	}
> +
> +	ret = platform_driver_register(&cci_devfreq_driver);
> +	if (ret)
> +		devfreq_remove_governor(&mtk_cci_devfreq_governor);
> +
> +	return ret;
> +}
> +module_init(mtk_cci_devfreq_init)

Use module_platform_driver

> +
> +static void __exit mtk_cci_devfreq_exit(void)
> +{
> +	int ret;
> +
> +	ret = devfreq_remove_governor(&mtk_cci_devfreq_governor);
> +	if (ret)
> +		pr_err("%s: failed to remove governor: %d\n", __func__, ret);
> +
> +	platform_driver_unregister(&cci_devfreq_driver);
> +}
> +module_exit(mtk_cci_devfreq_exit)
> +
> +MODULE_DESCRIPTION("Mediatek CCI devfreq driver");
> +MODULE_AUTHOR("Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>");
> +MODULE_LICENSE("GPL v2");
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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