Re: [PATCH RFC v6 2/9] PM / devfreq: Add generic imx bus scaling driver

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

Hi,

Also, I think that 'devfreq' word is not proper for device driver name.
imx-bus.c or imx-noc.c or others to inform the role of this driver of developer.

And, I have a question.
This driver adds the devfreq device with either passive governor
or userspace governor.

As I understood, the devfreq device with passive governor
will be operated with imx8m-ddrc.c driver.
But, when is operating with userspace governor?

I think that you better to add the explanation to description
for two scenarios how to operate with interconnect provider
on either passive governor or userspace governor usage case.

On 12/13/19 10:51 AM, Chanwoo Choi wrote:
> On 12/13/19 10:30 AM, Chanwoo Choi wrote:
>> Hi,
>>
>> On 11/15/19 5:09 AM, Leonard Crestez wrote:
>>> Add initial support for dynamic frequency switching on pieces of the imx
>>> interconnect fabric.
>>>
>>> All this driver does is set a clk rate based on an opp table, it does
>>> not map register areas.
>>>
>>> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
>>> ---
>>>  drivers/devfreq/Kconfig       |   9 ++
>>>  drivers/devfreq/Makefile      |   1 +
>>>  drivers/devfreq/imx-devfreq.c | 150 ++++++++++++++++++++++++++++++++++
>>>  3 files changed, 160 insertions(+)
>>>  create mode 100644 drivers/devfreq/imx-devfreq.c
>>>
>>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>>> index 923a6132e741..fef5ce831e90 100644
>>> --- a/drivers/devfreq/Kconfig
>>> +++ b/drivers/devfreq/Kconfig
>>> @@ -98,10 +98,19 @@ config ARM_IMX8M_DDRC_DEVFREQ
>>>  	select DEVFREQ_GOV_USERSPACE
>>>  	help
>>>  	  This adds the DEVFREQ driver for the i.MX8M DDR Controller. It allows
>>>  	  adjusting DRAM frequency.
>>>  
>>> +config ARM_IMX_DEVFREQ
>>> +	tristate "i.MX Generic DEVFREQ Driver"
>>> +	depends on ARCH_MXC || COMPILE_TEST
>>> +	select DEVFREQ_GOV_PASSIVE
>>> +	select DEVFREQ_GOV_USERSPACE
>>> +	help
>>> +	  This adds the generic DEVFREQ driver for i.MX interconnects. It
>>> +	  allows adjusting NIC/NOC frequency.
>>> +
>>>  config ARM_TEGRA_DEVFREQ
>>>  	tristate "NVIDIA Tegra30/114/124/210 DEVFREQ Driver"
>>>  	depends on ARCH_TEGRA_3x_SOC || ARCH_TEGRA_114_SOC || \
>>>  		ARCH_TEGRA_132_SOC || ARCH_TEGRA_124_SOC || \
>>>  		ARCH_TEGRA_210_SOC || \
>>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>>> index 3eb4d5e6635c..61d0edee16f7 100644
>>> --- a/drivers/devfreq/Makefile
>>> +++ b/drivers/devfreq/Makefile
>>> @@ -8,10 +8,11 @@ obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
>>>  obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
>>>  
>>>  # DEVFREQ Drivers
>>>  obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
>>>  obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)	+= imx8m-ddrc.o
>>> +obj-$(CONFIG_ARM_IMX_DEVFREQ)		+= imx-devfreq.o
>>>  obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>>>  obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra30-devfreq.o
>>>  obj-$(CONFIG_ARM_TEGRA20_DEVFREQ)	+= tegra20-devfreq.o
>>>  
>>>  # DEVFREQ Event Drivers
>>> diff --git a/drivers/devfreq/imx-devfreq.c b/drivers/devfreq/imx-devfreq.c
>>> new file mode 100644
>>> index 000000000000..620b344e87aa
>>> --- /dev/null
>>> +++ b/drivers/devfreq/imx-devfreq.c
>>> @@ -0,0 +1,150 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Copyright 2019 NXP
>>> + */
>>> +
>>> +#include <linux/clk.h>
>>> +#include <linux/devfreq.h>
>>> +#include <linux/device.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of_device.h>
>>> +#include <linux/pm_opp.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/slab.h>
>>> +
>>> +struct imx_devfreq {
>>> +	struct devfreq_dev_profile profile;
>>> +	struct devfreq *devfreq;
>>> +	struct clk *clk;
>>> +	struct devfreq_passive_data passive_data;
>>> +};
>>> +
>>> +static int imx_devfreq_target(struct device *dev,
>>> +			      unsigned long *freq, u32 flags)
>>
>> Don't use space for the indentation. Please use only tab.
>>
>>> +{
>>> +	struct imx_devfreq *priv = dev_get_drvdata(dev);
>>> +	struct dev_pm_opp *new_opp;
>>> +	unsigned long new_freq;
>>> +	int ret;
>>> +
>>> +	new_opp = devfreq_recommended_opp(dev, freq, flags);
>>> +	if (IS_ERR(new_opp)) {
>>> +		ret = PTR_ERR(new_opp);
>>> +		dev_err(dev, "failed to get recommended opp: %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +	new_freq = dev_pm_opp_get_freq(new_opp);
>>> +	dev_pm_opp_put(new_opp);
>>> +
>>> +	return clk_set_rate(priv->clk, new_freq);
>>> +}
>>> +
>>> +static int imx_devfreq_get_cur_freq(struct device *dev, unsigned long *freq)
>>> +{
>>> +	struct imx_devfreq *priv = dev_get_drvdata(dev);
>>> +
>>> +	*freq = clk_get_rate(priv->clk);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int imx_devfreq_get_dev_status(struct device *dev,
>>> +				      struct devfreq_dev_status *stat)
>>
>> ditto. Please use tab for the indentation.
>>
>>> +{
>>> +	struct imx_devfreq *priv = dev_get_drvdata(dev);
>>> +
>>> +	stat->busy_time = 0;
>>> +	stat->total_time = 0;
>>> +	stat->current_frequency = clk_get_rate(priv->clk);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static void imx_devfreq_exit(struct device *dev)
>>> +{
>>> +	dev_pm_opp_of_remove_table(dev);
>>> +}
>>> +
>>> +static int imx_devfreq_probe(struct platform_device *pdev)
>>> +{
>>> +	struct device *dev = &pdev->dev;
>>> +	struct imx_devfreq *priv;
>>
>> How about changing the variable name 'priv' to 'imx' or 'imx_data'?
>> because it is not easy to catch the role of 'priv' from variable name.
>>
>>> +	const char *gov = DEVFREQ_GOV_USERSPACE;
>>> +	void *govdata = NULL;
>>
>> How about changing the variable name 'govdata' to 'gov_data'?
>> - govdata -> gov_data
>>
>>> +	int ret;
>>> +
>>> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>>> +	if (!priv)
>>> +		return -ENOMEM;
>>> +
>>> +	priv->clk = devm_clk_get(dev, NULL);
>>
>> nitpick: because the clock-name is not mandatory.
>> Don't need to specify the clock name to inform the role of clock
>> of other developer/user?
>>
>> For example, "ddr", "bus" and so on.
> 
> And, this driver doesn't include the 'clk_prepare_enable'.
> how to enable the clock?
> 
>>
>>> +	if (IS_ERR(priv->clk)) {
>>> +		ret = PTR_ERR(priv->clk);
>>> +		dev_err(dev, "failed to fetch clk: %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +	platform_set_drvdata(pdev, priv);
>>> +
>>> +	ret = dev_pm_opp_of_add_table(dev);
>>> +	if (ret < 0) {
>>> +		dev_err(dev, "failed to get OPP table\n");
>>> +		return ret;
>>> +	}
>>> +
>>> +	priv->profile.polling_ms = 1000;
>>> +	priv->profile.target = imx_devfreq_target;
>>> +	priv->profile.get_dev_status = imx_devfreq_get_dev_status;
>>> +	priv->profile.exit = imx_devfreq_exit;
>>> +	priv->profile.get_cur_freq = imx_devfreq_get_cur_freq;
>>> +	priv->profile.initial_freq = clk_get_rate(priv->clk);
>>> +
>>> +	/* Handle passive devfreq parent link */
>>> +	priv->passive_data.parent = devfreq_get_devfreq_by_phandle(dev, 0);
>>> +	if (!IS_ERR(priv->passive_data.parent)) {
>>> +		dev_info(dev, "setup passive link to %s\n",
>>> +			 dev_name(priv->passive_data.parent->dev.parent));
>>> +		gov = DEVFREQ_GOV_PASSIVE;
>>> +		govdata = &priv->passive_data;
>>> +	} else if (priv->passive_data.parent != ERR_PTR(-ENODEV)) {
>>> +		// -ENODEV means no parent: not an error.
>>> +		ret = PTR_ERR(priv->passive_data.parent);
>>> +		if (ret != -EPROBE_DEFER)
>>> +			dev_warn(dev, "failed to get initialize passive parent: %d\n",
>>> +				 ret);
>>> +		goto err;
>>> +	}
>>
>> You better to change the exception handling as following: It is more simple.
>>
>> 	} else if (PTR_ERR(priv->passive_data.parent) == -EPROBE_DEFER)
>> 			|| PTR_ERR(priv->passive_data.parent) == -ENODEV) {
>> 		goto err;
>> 	} else {
>> 		ret = PTR_ERR(priv->passive_data.parent);
>> 		dev_err(dev, "failed to get initialize passive parent: %d\n", ret);
>> 		goto err;
>> 	}
>>
>>> +
>>> +	priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
>>> +						gov, govdata);
>>> +	if (IS_ERR(priv->devfreq)) {
>>> +		ret = PTR_ERR(priv->devfreq);
>>> +		dev_err(dev, "failed to add devfreq device: %d\n", ret);
>>> +		goto err;
>>> +	}
>>> +
>>> +	return 0;
>>> +
>>> +err:
>>> +	dev_pm_opp_of_remove_table(dev);
>>> +	return ret;
>>> +}
>>> +
>>> +static const struct of_device_id imx_devfreq_of_match[] = {
>>> +	{ .compatible = "fsl,imx8m-noc", },
>>> +	{ .compatible = "fsl,imx8m-nic", },
>>> +	{ /* sentinel */ },
>>> +};
>>> +MODULE_DEVICE_TABLE(of, imx_devfreq_of_match);
>>> +
>>> +static struct platform_driver imx_devfreq_platdrv = {
>>> +	.probe		= imx_devfreq_probe,
>>> +	.driver = {
>>> +		.name	= "imx-devfreq",
>>> +		.of_match_table = of_match_ptr(imx_devfreq_of_match),
>>> +	},
>>> +};
>>> +module_platform_driver(imx_devfreq_platdrv);
>>> +
>>> +MODULE_DESCRIPTION("Generic i.MX bus frequency driver");
>>
>> If this driver is for bus frequency, you better to use 'bus' for the clock-name
>> for the readability.
>>
>>> +MODULE_AUTHOR("Leonard Crestez <leonard.crestez@nxp.com>");
>>> +MODULE_LICENSE("GPL v2");
>>>
>>
>>
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics