Re: [PATCH v2 4/4] devfreq: add mediatek cci devfreq

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

Hi Andrew-sh.Cheng,

Please add the dt-binding documentation.

On 19. 3. 29. 오후 3:46, Andrew-sh.Cheng wrote:
> 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 | 235 +++++++++++++++++++++++++++++++++++
>  3 files changed, 246 insertions(+)
>  create mode 100644 drivers/devfreq/mt8183-cci-devfreq.c
> 
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index 6a172d3..da2f8ec 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -91,6 +91,16 @@ 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 "Tegra DEVFREQ Driver"
>  	depends on ARCH_TEGRA_124_SOC
> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> index 32b8d4d..817dde7 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)		+= tegra-devfreq.o
>  
> diff --git a/drivers/devfreq/mt8183-cci-devfreq.c b/drivers/devfreq/mt8183-cci-devfreq.c
> new file mode 100644
> index 0000000..af82d2e
> --- /dev/null
> +++ b/drivers/devfreq/mt8183-cci-devfreq.c
> @@ -0,0 +1,235 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019 MediaTek Inc.

You can add the author information under copyright information.

> + */
> +
> +#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;

Just use the space instead of tab as following:

	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)
> +{
> +	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);
> +			update_devfreq(cci_df->devfreq);

Please handle the return value of update_devfreq() for exception handling.

> +			mutex_unlock(&cci_df->devfreq->lock);
> +		}
> +	}
> +
> +	if ((val & REGULATOR_EVENT_ABORT_VOLTAGE_CHANGE) &&

if -> else if

At the same time, receives only one notification.
It is not necessary to check the two if statement always, .


> +	    ((unsigned long)data > cci_df->proc_reg_uV)) {
> +		cci_df->proc_reg_uV = (unsigned long)data;
> +		mutex_lock(&cci_df->devfreq->lock);
> +		update_devfreq(cci_df->devfreq);

ditto. Please check the return value of update_devfreq.

> +		mutex_unlock(&cci_df->devfreq->lock);
> +	}
> +
> +	/* deal with increase frequency */
> +	if ((val & REGULATOR_EVENT_VOLTAGE_CHANGE) &&

ditto.
if -> else if

At the same time, receives only one notification.
It is not necessary to check the two if statement always, .


> +	    (cci_df->proc_reg_uV < (unsigned long)data)) {
> +		cci_df->proc_reg_uV = (unsigned long)data;
> +		mutex_lock(&cci_df->devfreq->lock);
> +		update_devfreq(cci_df->devfreq);

ditto. Please check the return value of update_devfreq.

> +		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_max_freq_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)
> +{
> +	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;
> +		regulator_register_notifier(cci_df->proc_reg,
> +					    nb);

Please check the return value of regulator_register_notifier
in order to handle the exception handling.


> +		break;
> +
> +	case DEVFREQ_GOV_STOP:
> +	case DEVFREQ_GOV_SUSPEND:
> +		regulator_unregister_notifier(cci_df->proc_reg,
> +					    nb);

ditto.

> +

Remove unneeded blank line.

> +		break;
> +
> +	default:
> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +static struct devfreq_governor mtk_cci_devfreq_governor = {
> +	.name = "mtk_cci_vmon",

How about editing the name from mtk_cci_vmon to mediatek_cci_voltage_monitor
for the readability? Actually, 'mtk' and 'vmon' are not standard expression.

> +	.get_target_freq = mtk_cci_governor_get_target,
> +	.event_handler = mtk_cci_governor_event_handler,

Please add following code to make it as the immutable
because the governor for this driver will not be changed
through sysfs interface.

	.immutable = true

> +};
> +
> +static int mtk_cci_devfreq_target(struct device *dev, unsigned long *freq,
> +				  u32 flags)
> +{
> +	struct cci_devfreq *cci_df = dev_get_drvdata(dev);
> +
> +	if (!cci_df)
> +		return -EINVAL;
> +
> +	clk_set_rate(cci_df->cci_clk, *freq);

Please check the return value of clk_set_rate().

> +
> +	return 0;
> +}
> +
> +static struct devfreq_dev_profile cci_devfreq_profile = {
> +	.target		= mtk_cci_devfreq_target,

Just use the space instead of tab because cci_devfreq_profile
only has one record.

	.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 = clk_get(cci_dev, "cci_clock");

clk_get -> devm_clk_get()

> +	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);
> +

Remove unneeded blank line.

> +		return ret;
> +	}> +
> +	cci_df->proc_reg = regulator_get_optional(cci_dev, "proc");


regulator_get_optional -> devm_regulator_get_optional

> +	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);
> +

Remove unneeded blank line.

> +		goto err_put_clk;

If you use devm_clk_get(), just return instead of goto.

> +	}
> +
> +	ret = dev_pm_opp_of_add_table(&pdev->dev);
> +	if (ret) {
> +		dev_err(cci_dev, "Fail to init CCI OPP table\n");
> +		goto err_put_reg;
> +	}
> +
> +	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)) {
> +		dev_err(cci_dev, "cannot create cci devfreq device\n", ret);
> +		goto err_put_reg;
> +	}
> +
> +	return 0;
> +
> +err_put_reg:
> +	regulator_put(cci_df->proc_reg);
> +err_put_clk:
> +	clk_put(cci_df->cci_clk);

If you use devm_clk_get()/devm_regulator_get(),
'err_put_reg' and 'err_put_clk' are unneeded.

> +
> +	return ret;
> +}
> +
> +static const 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 = 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)
> +
> +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