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

[Chanwoo Choi]

Hi,

On 3/23/21 8:33 PM, Andrew-sh.Cheng wrote:
> From: "Andrew-sh.Cheng" <andrew-sh.cheng@xxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxx>
> ---
>  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@xxxxxxxxxxxx>
> + */
> +
> +#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;

nitpick. how about using 'old_voltage'?
because 'vproc' is not easy for understanding.

> +	unsigned long old_freq;
> +};
> +
> +static int mtk_cci_set_voltage(struct cci_devfreq *cci_df, int vproc)

nitpick: how about changing 'vproc -> voltage'?

> +{
> +	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);

Use dev_err_probe() to handle EPROBE_DEFER case. It makes code more simple.

> +		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);

ditto. Use dev_err_probe()

> +		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);

Why do you call this function without registration?
If you want to catch the OPP changes of devfreq,
you can use devfreq_register_opp_notifier/devfreq_unregister_opp_notifier
functions.

> +	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[] = {

Need to change it as following at same line:
static const __maybe_unused struct of_device_idmediatek_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@xxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL v2");
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics