Message-ID: <3ff7ac1c-6234-1b82-d38d-389906d295e9@samsung.com>
Date:   Tue, 12 Feb 2019 13:06:55 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Andrew-sh Cheng <andrew-sh.cheng@...iatek.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        srv_heupstream@...iatek.com, fan.chen@...iatek.com
Subject: Re: [PATCH 3/3] devfreq: add mediatek cci devfreq

Hi Andrew-sh.Cheng,

On 19. 1. 29. 오후 3:35, Andrew-sh Cheng wrote:
> From: "Andrew-sh.Cheng" <andrew-sh.cheng@...iatek.com>
> 
> For big/little cpu cluster architecture,
> not only CPU frequency, but CCI frequency will also affect performance.
> 
> Little cores and cci share the same buck in Mediatek mt8183 IC,
> so we add a CCI devfreq which will get notification when buck voltage
> is changed, then CCI devfreq can set cci frequency as high as possible.
> 
> Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@...iatek.com>
> ---
>  drivers/devfreq/Kconfig              |   9 ++
>  drivers/devfreq/Makefile             |   1 +
>  drivers/devfreq/mt8183-cci-devfreq.c | 224 +++++++++++++++++++++++++++++++++++
>  3 files changed, 234 insertions(+)
>  create mode 100644 drivers/devfreq/mt8183-cci-devfreq.c
> 
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index 6a172d3..0b14aab 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -113,6 +113,15 @@ config ARM_RK3399_DMC_DEVFREQ
>            It sets the frequency for the memory controller and reads the usage counts
>            from hardware.
>  
> +config ARM_MT8183_CCI_DEVFREQ
> +	tristate "MT8183 CCI DEVFREQ Driver"
> +	depends on ARM_MEDIATEK_CPUFREQ
> +	help
> +		This adds devfreq for cci clock
> +		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.
> +

Move ARM_MT8183_CCI_DEVFREQ under ARM_EXYNOS_BUS_DEVFREQ.
On later, I'll change the order between ARM_TEGRA_DEVFREQ and ARM_RK3399_DMC_DEVFREQ
alphabetically. So, you better to keep the order of name.


>  source "drivers/devfreq/event/Kconfig"
>  
>  endif # PM_DEVFREQ
> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> index 32b8d4d..25afe8c 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_ARM_MT8183_CCI_DEVFREQ)	+= mt8183-cci-devfreq.o

Move it under obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ).

>  
>  # DEVFREQ Event Drivers
>  obj-$(CONFIG_PM_DEVFREQ_EVENT)		+= event/
> diff --git a/drivers/devfreq/mt8183-cci-devfreq.c b/drivers/devfreq/mt8183-cci-devfreq.c
> new file mode 100644
> index 0000000..4837892
> --- /dev/null
> +++ b/drivers/devfreq/mt8183-cci-devfreq.c
> @@ -0,0 +1,224 @@
> +// SPDX-License-Identifier: GPL-2.0
> +//
> +// Copyright (c) 2018 MediaTek Inc.

Add blank line and change year 2018 -> 2019.

> +#include <linux/cpu.h>
> +#include <linux/cpufreq.h>

This driver doesn't use any helper function of cpufreq.h/cpu.h.
It depends on devfreq/regulator framework. Please remove them.

> +#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_data {
> +	struct devfreq		*devfreq;
> +	struct regulator	*proc_reg;
> +	struct clk		*cci_clk;
> +	unsigned long		buck_volt;
> +	int			volt_increasing;
> +	struct notifier_block	nb;
> +};
> +
> +static int mtk_cci_governor_get_target(struct devfreq *devfreq,
> +				       unsigned long *freq)
> +{
> +	struct cci_devfreq_data *cci_devdata;
> +	int	i, opp_count;
> +	struct dev_pm_opp	*opp;
> +	unsigned long	opp_rate, opp_voltage;

Above three definitions use the tab for indentation. Please use space.

> +
> +	cci_devdata = dev_get_drvdata(devfreq->dev.parent);
> +
> +	/* find available frequency */
> +	opp_count = dev_pm_opp_get_opp_count(devfreq->dev.parent);
> +	for (i = 0, opp_rate = ULONG_MAX; i < opp_count; i++, opp_rate--) {
> +		opp = dev_pm_opp_find_freq_floor(devfreq->dev.parent,
> +						 &opp_rate);
> +		opp_voltage = dev_pm_opp_get_voltage(opp);
> +		dev_pm_opp_put(opp);
> +
> +		if (opp_voltage <= cci_devdata->buck_volt)
> +			break;
> +	}
> +	*freq = opp_rate;
> +
> +	return 0;
> +}
> +
> +static int mtk_cci_governor_event_handler(struct devfreq *devfreq,
> +					  unsigned int event, void *data)
> +{
> +	return 0;
> +}

The devfreq core enables the governor with using DEVFREQ_GOV_START.
But, this driver just start after proving the device driver. It break
the previous sequence of governor.

So, if you register/unregister the regulator as following,
it can keep the existing sequence for governor starting.

	case DEVFREQ_GOV_START:
	case DEVFREQ_GOV_RESUME:
		regulator_register_notifier(...);

	case DEVFREQ_GOV_STOP:
	case DEVFREQ_GOV_SUSPEND:
		regulator_unregister_notifier(...);
		break;

> +
> +static struct devfreq_governor mtk_cci_devfreq_governor = {
> +	.name = "voltage_monitor",
> +	.get_target_freq = mtk_cci_governor_get_target,
> +	.event_handler = mtk_cci_governor_event_handler,
> +};
> +
> +static int mtk_cci_devfreq_target(struct device *dev, unsigned long *freq,
> +				  u32 flags)
> +{
> +	struct cci_devfreq_data *cci_devdata;
> +
> +	cci_devdata = dev_get_drvdata(dev);

You better to modify it as following:

	struct cci_devfreq_data *cci_devdata = dev_get_drvdata(dev);
	
	if (!cci_devdata)
		return -EINVAL;

> +
> +	clk_set_rate(cci_devdata->cci_clk, *freq);
> +
> +	return 0;
> +}
> +
> +static struct devfreq_dev_profile cci_devfreq_profile = {
> +	.polling_ms	= 0,

Dont' need to initialize it as zero. just remove this line.

> +	.target		= mtk_cci_devfreq_target,
> +};
> +
> +static int cci_devfreq_regulator_notifier(struct notifier_block *nb,
> +					  unsigned long val, void *data)
> +{
> +	struct cci_devfreq_data *cci_devdata =
> +		container_of(nb, struct cci_devfreq_data, nb);
> +
> +	/* deal with reduce frequency */
> +	if (val & REGULATOR_EVENT_PRE_VOLTAGE_CHANGE) {
> +		struct pre_voltage_change_data *pvc_data = data;
> +
> +		if (pvc_data->old_uV > pvc_data->min_uV) {
> +			cci_devdata->volt_increasing = 0;

IMO, 'volt_increasing' is not clear. Instead, cci_devdata
could have the 'previous_voltage' variable instead of volt_increasing.
And you could use 'previous_voltage' for comparision.

> +			cci_devdata->buck_volt =
> +				(unsigned long)(pvc_data->min_uV);
> +			mutex_lock(&cci_devdata->devfreq->lock);
> +			update_devfreq(cci_devdata->devfreq);
> +			mutex_unlock(&cci_devdata->devfreq->lock);
> +		} else {
> +			cci_devdata->volt_increasing = 1;
> +		}
> +	}
> +	/* deal with abort reduce frequency */
> +	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, .



> +	    /* deal with increase frequency */
> +	    ((val & REGULATOR_EVENT_VOLTAGE_CHANGE) &&
> +	     cci_devdata->volt_increasing == 1)) {
> +		cci_devdata->buck_volt = (unsigned long)data;
> +		mutex_lock(&cci_devdata->devfreq->lock);
> +		update_devfreq(cci_devdata->devfreq);
> +		mutex_unlock(&cci_devdata->devfreq->lock);
> +	}
> +
> +	return 0;
> +}
> +
> +static int mtk_cci_devfreq_probe(struct platform_device *pdev)
> +{
> +	struct device *cci_dev = &pdev->dev;
> +	struct cci_devfreq_data *cci_devdata;
> +	struct notifier_block *nb;
> +	int ret;
> +
> +	dev_pm_opp_of_add_table(&pdev->dev);

Move it after getting clock/regulator. After checking that all resourcess are available,
and then you better to get the opp table. And check the return value  of dev_pm_opp...()

> +
> +	cci_devdata = devm_kzalloc(cci_dev, sizeof(*cci_devdata), GFP_KERNEL);
> +	if (!cci_devdata)
> +		return -ENOMEM;
> +	nb = &cci_devdata->nb;
> +	cci_devdata->cci_clk = ERR_PTR(-ENODEV);

It should be handled when error happen. It is not good for readability.

> +	cci_devdata->proc_reg = ERR_PTR(-ENODEV);

ditto.

> +
> +	cci_devdata->cci_clk = clk_get(cci_dev, "cci_clock");
> +	ret = PTR_ERR_OR_ZERO(cci_devdata->cci_clk);
> +	if (ret) {
> +		if (ret == -EPROBE_DEFER)
> +			pr_err("cci clock not ready, retry\n");

You should use 'dev_err' instead of pr_err on this driver.

I think that don't show the error when EPROBE_DEFER. you better to just return.

> +		else
> +			pr_err("no clock for cci: %d\n", ret);

How about changing the log like below?
"failed to get clock for CCI"

pr_err -> dev_err

> +
> +		goto out_free_resources;
> +	}
> +
> +	cci_devdata->proc_reg = regulator_get_optional(cci_dev, "proc");
> +	ret = PTR_ERR_OR_ZERO(cci_devdata->proc_reg);
> +	if (ret) {
> +		if (ret == -EPROBE_DEFER)
> +			pr_err("cci regulator not ready, retry\n");

ditto.

> +		else
> +			pr_err("no regulator for cci: %d\n", ret);

How about changing the log like below?
"failed to get regulator for CCI"

> +
> +		goto out_free_resources;
> +	}
> +
> +	platform_set_drvdata(pdev, cci_devdata);
> +
> +	/* create cci_devfreq and add to cci device.
> +	 * governor is voltage_monitor.
> +	 * governor will get platform_device data to make decision.
> +	 */

I think that you don't need to explain the kind of governor and how to
decide the next frequency by governor. It is enough to call the devm_devfreq_add_device.

> +	cci_devdata->devfreq = devm_devfreq_add_device(cci_dev,
> +						       &cci_devfreq_profile,
> +						       "voltage_monitor",
> +						       NULL);
> +
> +	nb->notifier_call = cci_devfreq_regulator_notifier;
> +	regulator_register_notifier(cci_devdata->proc_reg,
> +				    nb);

As I commented, regulator_register_notifier() should be handled in event_handler function.

> +
> +	return 0;
> +
> +out_free_resources:
> +	if (!IS_ERR(cci_devdata->cci_clk))
> +		clk_put(cci_devdata->cci_clk);
> +	if (!IS_ERR(cci_devdata->proc_reg))
> +		regulator_put(cci_devdata->proc_reg);
> +
> +	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 = 0;
> +
> +	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 = 0;
> +
> +	platform_driver_unregister(&cci_devfreq_driver);
> +
> +	ret = devfreq_remove_governor(&mtk_cci_devfreq_governor);
> +	if (ret)
> +		pr_err("%s: failed to remove governor: %d\n", __func__, ret);
> +}
> +module_exit(mtk_cci_devfreq_exit)
> +
> +MODULE_LICENSE("GPL v2");

nitpick. better to move it under MODULE_AUTHOR("")

> +MODULE_DESCRIPTION("Mediatek CCI devfreq driver");
> +MODULE_AUTHOR("andrew-sh.cheng");

Add full name and email as following:
- MODULE_AUTHOR("Andrew-sh.Cheng <andrew-sh.cheng@...iatek.com>"


> +
> 

Remove unneeded blank line.


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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